Units, Symbols, and Terminology for Plant Physiology: A Reference for Presentation of Research Results in the Plant Sciences

UNITS, SYMBOLS , AND TERMINOLOG Y FOR PLAN T PHYSIOLOG Y

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UNITS, SYMBOLS , AND TERMINOLOGY FOR PLAN T PHYSIOLOG Y A Reference for Presentation of Research Results in the Plant Sciences Sponsored b y the International Association fo r Plant Physiology

Frank B. Salisbury , Edito r Utah State University

New York Oxfor d Oxford Universit y Press 1996

Oxford Universit y Pres s Oxford Ne w York Athens Aucklan d Bangko k Bogot a Bomba y Buenos Aire s Calcutt a Cap e Town Da r es Salaa m Delhi Florenc e Hon g Kon g Istanbu l Karach i Kuala Lumpur Madra s Madri d Melbourn e Mexico Cit y Nairob i Pari s Singapor e Taipei Toky o Toront o and associate d companie s in Berlin Ibada n

Copyright © 199 6 b y Oxford Universit y Press, Inc . Published b y Oxfor d Universit y Press, Inc . 198 Madison Avenue , Ne w York, New York 1001 6 Oxford i s a registered trademark of Oxford Universit y Press All right s reserved. No part o f thi s publication may be reproduced , stored in a retrieval system , or transmitted, i n an y form o r means , electronic, mechanical , photocopying , recording , o r otherwise , without th e prior permissio n o f Oxford Universit y Press . Library o f Congress Cataloging-in-Publication Dat a Units, symbols, an d terminology fo r plant physiology : a reference fo r presentation o f research result s in the plant sciences / sponsore d b y the International Association for Plan t Physiolog y ; Frank B . Salisbury, editor . p. cm . Includes bibliographical reference s an d index. ISBN 0-19-509445- X 1. Plan t physiology—Terminology . 2 . Botany—Terminology . 3. Technical writing . I. Salisbury, Fran k B. II. International Association fo r Plan t Physiology . QK710.5.U55 199 6 581.1'014—dc20 95-5059 3

9 8 7 6 5 4 3 2 1 Printed i n th e Unite d State s o f America on acid-fre e pape r

CONTENTS CONTRIBUTORS vii

i

PREFACE

ix

SECTION L THE BASICS

1

1. Summary of the International System of Units (SI Units) Salisbury Quantities and Units 4 Le Systeme International D'Unites (SI) 5 The SI Tables 6 Some Special Considerations 1

3

2. Rules for Botanical Nomenclature McNeill & Barkworth 2 Documentation 2 Taxonomic Groups (Taxa; singular: Taxon) : Som e Rules of Nomenclature Form of Scientific Names 2 Special Situation s 2

1 1 22 2 4

3

3. Statistics Sisson 2 General terms: 2 Measures of Central Tendency 2 Variability 2 Confidence Intervals 2 Test of Hypothesis 3 Regression Analysi s 3 Analysis of Variance 3 Covariance Analysis 3 Nonparametric Test s 4 Miscellaneous 4

7 7 7 8 9 0 1 2 8 0 1

SECTION II: PLANT BIOPHYSICS

43

4. Basic Thermodynamic Quantities Savage 4 Basic Concepts and the Chemical Potential 4 Free Energy and Water Potential 4 Enthalpy 5 Water Potential in the Vapor State 5 Components of Water Potential 5 Water Potential of Aqueous Solutions 5 Theory of the Pressure-Chamber Apparatu s 5

5 5 7 0 0 1 3 3

vi Contents 5. Solutions (Ionic Relations) Dainty 5 Abbreviations Use d as Subscripts an d Superscripts 5 The Tables 5

5 5 6

6. Water Relations Dainty 6 The Tables 6

0 0

7. Energy Transfer Salisbury & Savage 6 Terms, Symbols, an d Units Appropriate in Energy-Transfer Studies 6 Some Equations Used in Heat-Transfer Studies 6

5 5 8

8. Phloem Transport Geiger & van Bel 7 The Tables 7

2 2

9. Electromagnetic Radiation Krizek & Sager 7 The Tables 7

5 5

SECTION III. PLANT BIOCHEMISTRY AND MOLECULAR BIOLOGY 7

9

10. Plant Biochemistry Black 8 Instructions o n Chemical and Mathematical Usage 8 Abbreviations an d Symbols 8 The Tables 8

1 1 4 6

11. Plant Molecular Biology and Gene Designations Reardon & Price 9 Terminology 9 Gene Designations 10

7 7 5

SECTION IV: PLANT GROWTH AND DEVELOPMENT

109

12. Morphogenesis and the Kinetics of Plant Growth Erickson 11 The Biometry of Growth 11 Shoot and Root Morphogenesis 11

1 1 3

13. Growth Analysis and Yield Components Bugbee 11

5

14. Plant Movements Haupt 12 Types and Mechanisms o f Movement 12 Control of Movement: Genera l 12 Terms for Induced Movements (Type s of Response) 12 Stimuli 12 Direction o r Sense of Response 12 Terms for Autonomous Movements 12

0 0 1 2 3 4 4

15. Growth Substances Cleland 12

6

16. Biological Timing Koukkari & Sweeney 12

9

17. Dormancy, Photoperiodism, and Vernalization Salisbury 13

4

General Considerations 11 Units for Growth Analysis and Yield Components 11

18. Stress Physiology Fuchigami, Maas, Lyons, Rains, Raison, & Shackel General Stress-Physiolog y Terms 14

5 6

142 3

Contents vi Chilling Injury 14 Cold Hardiness 14 Water Stress 15 Salinity Stress 15 APPENDICES: PRESENTING SCIENTIFIC DATA 16 A. Some Suggestions About Scientific Writing Salisbury 16 The Sentence 16 Modifying Words 16 Modifying Phrases and Clauses 17 Verbs 17 Some Further Notes about Punctuation 17 Abbreviations 17 Unnecessary Words 17 Words with Special Problems 17 Some Suggestions about Format and Word Processors 18 Summary 18 B. Standards for Effective Presentations Koning Slide Presentations 18 Poster Presentations 19

i 4 6 1 4 1 3 4 8 2 5 6 8 8 9 3 5

188 9 5

C. Guidelines for Measuring and Reporting Environmental Parameters for Plant Experiments in Growth Chambers Sager, Krizek, Tibbitts 202 Purpose and scope 20 2 Introduction 20 3 Definitions 20 3 Instrumentation 20 6 Measurement Technique 20 7 Reporting 20 8 Synoptic Table 21 0 INDEX

217

CONTRIBUTORS Mary Barkworth, Utah State University, U.S.A. Clanton C. Black, University of Georgia, U.S.A. Bruce G. Bugbee, Utah State University, U.S.A. Robert E. Cleland, University of Washington, U.S.A. Jack Dainty, University of Toronto, Canada Ralph O. Erickson, University of Pennsylvania, U.S.A. Leslie H. Fuchigami, Oregon Stat e University, U.S.A. Donald R. Geiger, University of Dayton, Ohio, U.S.A. Wolfgang W. Haupt, Universtat Erlangen-Nurnberg, Germany Ross E. Koning, Eastern Connecticut University, U.S.A. Willard L. Koukkari, University of Minnesota, U.S.A. Donald T. Krizek, U.S. Department of Agriculture, Beltsville, Maryland, U.S.A. James M. Lyons, University of California, Davis, California, U.S.A. Eugene V . Maas, U.S. Salinity Laboratory, USDA-ARS, Riverside, California, U.S.A. John McNeill, Royal Ontario Museum, Toronto, Canada Carl A. Price, Rutgers University, New Jersey, U.S.A. William Rains, University of California, Davis, California, U.S.A. John K. Raison, Macquarie University, North Ryde, Australia (deceased) Ellen Reardon, Rutgers University, New Jersey, U.S.A. John C. Sager, Kennedy Space Center, Florida, U.S.A. Frank B. Salisbury, Utah State University, U.S.A. Michael J. Savage, University of Natal, Pietermaritzburg, Republic of South Africa. Kenneth Shackel, University of California, Davis, California, U.S.A. Donald Sisson, Utah State University, U.S.A. Beatrice M. Sweeney, University of California a t Santa Barbara, U.S.A. (deceased) Theodore W. Tibbitts, University of Wisconsin-Madison, U.S.A. Aart J.E. van Bel, Justus-Liebig Universitat, Giessen, Germany

PREFACE When one person wishes to communicate some information directly to another person, it is essential that the two speak the same language; that is, the words and symbols must have the same meaning for both persons. Suc h a thought provides one motivation for the preparation of this book, which is designed t o be a reference sourc e for plant physiologists and other plant scientists who are preparing their research results for publication or other presentation. Th e primary goal is to provide information about the use of units, symbols, and terminology in the plant sciences , especiall y plan t physiology. I n addition , w e als o provide som e hint s an d instructions abou t writing and the preparation of posters and slide presentations for scientific meetings, including a format for presentation of growth-chamber data. Section I introduces the basics. It s three chapters consider the use of SI units, rules for botanical nomenclature, and basic principles of statistics. Section s II, III, and IV present more detail i n the field s o f plant biophysics, biochemistry , and growth and development. Thes e sections emphasize SI units whenever that is appropriate, but they also contain many lists of terms that are used in the plant sciences. Th e appendices contain the hints and instructions for writing an d for preparing posters an d slide presentations, plus a summary of guidelines for reporting environmental parameter s for plant experiments in controlled environments. Th e chapter on biochemistry was modified from The Journal o f Biological Chemistry; i t is included here as a handy reference. Appendi x C was also prepared for another publication. Al l other sections were originally prepared for this volume. Each chapter was first prepared by one or more specialists in the field, and the authors then sent their chapters to several colleagues. A s a result, the present chapters represent a t least the beginnings o f a consensu s abou t th e term s an d sometime s symbol s within eac h subfield . Although th e tim e when al l plan t scientist s agre e o n al l units , symbols, terminology , an d presentation techniques may be in the distant future (i f it ever arrives), it is hoped that this book will bring us closer t o such a meeting of the minds. Afte r I had edited the manuscripts sent by the various authors, the entire book was sent to each author, who often commented about some chapters beside s hi s o r he r own . Thi s process wa s repeate d severa l time s over a period exceeding a decade (mostly because the project was set aside several times while other projects

x Preface were being completed). Durin g this long gestation period, two authors died and several other s retired! I n spite of the long period from conception t o birth, every chapter includes significant changes mad e shortly before publication. Th e book presents the most current thinking of its authors and editor. The chapters tha t include definitions of terms follow two different approaches : I n some chapters, terms ar e arranged alphabetically; in others they follow an order in which one term builds upon the preceding term or terms (a mini-review of the subject). Th e choice of approach depended upon the author and the subject matter, In the non-alphabetical cases, the number of terms is rather limited s o that it should be relatively easy to find a term by scanning the lists. A few references ar e presented, especially where definitions ar e somewhat controversial. And controversy remains in plant physiology! Pleas e submi t suggestions for future edition s to me or to the appropriate chapter author . We have tried to remove inconsistencies an d contradictions althoug h some seem to be inevitable. W e are aware of considerable redundancy, which should make the booklet easier to use as a reference source. A n editorial inconsistency tha t I have decided to allow concerns the use of references. Man y show only initials of authors, but when given names were known to me, I included them. W e have followed a reference style that includes written-out journal names rather tha n abbreviations and more punctuation than is used in many current journals. Thi s takes a little more space, but we believe it will make it easier for a reader to use the references. Several secretaries were involved with the manuscript, but Laura Wheelwright did much formatting, an d Mary Ann Clark must have spent the equivalent of an intense, full-time year working on the final formatting of camera-ready copy with much direction from Kirk Jensen, a Senio r Edito r a t th e Oxfor d University Press. Th e author s an d I wish t o expres s muc h appreciation to those diligent secretaries; their efforts wer e often "above an d beyond the call of duty." F.B. Salisbury Logan, Utah

APPROXIMATE CONVERSIONS: METRIC Temperature

Length

Mass

U.S.a Volume

° This char t was prepared by F.B.S. for: Fran k B. Salisbury and Cleon W. Ross. 1969 . Plan t Physiology First Edition. Wadswort h Publishing Co., Inc., Belmont, California. I t was not used in subsequent edition s Some letters have been changed to reflect the conventions presented in this book.

GREEK ALPHABET AND ENGLISH EQUIVALENTS Greek letter (roman)

A B

Greek letter (italic)

Greek name

A B

Alpha Beta

a b

Gamma

g d e z

Delta

E Z H

E Z H

Epsilon Zeta

Eta Theta

I K

I

Iota

K

Kappa Lambda

M N

M N

0

O

Mu Nu Xi

ks, x

P r s t

P

T

T

Tau

Sigma Upsilon

Phi Chi Psi Omega

aAt end of word.

th i k 1 m n o

P

X

e(e)

Omicron

Pi Rho

X

English equivalent (phonetic)

y

f, ph ch, kh ps o(o)

UNITS, SYMBOLS , AND TERMINOLOG Y FOR PLAN T PHYSIOLOG Y

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I THE BASICS This sectio n deals mostl y with constructed scientifi c languages. Ho w do people who want t o communicat e usuall y achiev e a commo n language ? Mostly , we begi n a s infants an d jus t us e th e languag e unti l meaning s becom e clear . Bu t ther e ar e problems wit h thi s approach . Fo r on e thing , people i n different part s o f societydifferent geographica l areas , fo r example—hav e forme d differen t languages . Furthermore, usag e ofte n produce s language s that lac k logi c an d consistency . A s scientists, w e would like to communicate effectively with everyone else on the plane t who migh t share our commo n interests . One solution tha t seem s to be fallin g into place withou t an y directe d effor t i s th e broadenin g acceptanc e o f Englis h a s th e language o f scienc e (an d muc h o f commerce , etc.) . A second solutio n fo r scienc e has involve d a consciou s an d directe d menta l effor t t o create consistenc y an d uniformity. Group s o f scientists hav e tried t o fin d way s to agree o n ho w to expres s physical quantities , nomenclatur e o f organisms, and mathematica l symbols (among other things) . I n thi s section, w e present th e thre e constructe d language s that dea l with physica l quantities , taxonomi c nomenclature, and statistics: 1. Th e Internationa l Syste m of Unit s for expressin g physical quantities , 2. Th e adopte d convention s for naming plant material; that is , many of th e important rule s o f taxonomi c nomenclatur e agree d upo n i n Botanica l Congresses, an d 3. Statistica l procedure s an d thei r notations ; thes e provid e a measur e o f significance. All plan t scientist s wh o wor k with quantitativ e measurements, regardles s o f thei r specialty withi n th e fiel d o f plant physiology or i n other area s o f botany, need t o b e conversant wit h thes e two international system s of communication plu s the mean s of evaluatin g th e reliabilit y of their numerica l data.

1 THE INTERNATIONAL SYSTEM OF UNITS (SI UNITS)1 Frank B . Salisbury Plants, Soils , an d Biometeorology Departmen t Utah Stat e University Logan, Uta h 84322-4820 , U.S.A . As modern scienc e cam e into being , it depended mor e and more upon the accurat e measurement o f physica l quantities . Suc h measuremen t require s a syste m o f standards that i s recognized an d accepted b y all those who would communicate their measurements t o eac h other . I n respons e t o thi s need , th e metric syste m o f measurement wa s devised durin g the Frenc h Revolutio n (178 9 t o 1799) . I t was an attempt to devis e a decima l syste m of measure s tha t woul d simplif y and unif y calculations. Nearl y a centur y later, recognizin g the nee d t o furthe r improv e th e system, th e Bureau International des Poids e t Mesures (BIPM ) was se t u p b y th e Convention du Metre signe d in Paris in 187 5 by seventeen States ; the Convention was amended i n 1921 . Th e tas k o f th e BIP M i s t o ensur e worldwid e unificatio n o f physical measurements . I t operates in offices an d laboratories in Sevres, near Paris, France, unde r supervisio n of the Comite International des Poids e t Mesures (CIPM) , which consist s o f 1 8 members, each fro m a different State . Th e CIP M itself come s under the authorit y of the Conference General e de s Poids e t Mesures (CGPM) , which consists o f delegates fro m al l the Membe r States (4 6 States i n March, 1991 ) o f th e Convention du Metre. Th e CGP M meets a t present ever y four years , but th e CIP M meets ever y year. By th e mi d twentiet h century , th e metri c syste m wa s bein g widel y use d i n science, bu t i n many cases, individua l branches of science ha d developed thei r own specialized unit s an d terms . Fo r example , th e CG S (centimeter.gram.second ) system o f mechanical units , used especially in physics, included such terms a s dyne, erg, poise , stokes , gauss , oersted, an d maxwel l (all no w considered obsolete) . T o

1

Earl y version s o f thi s chapte r wer e publishe d as Appendi x A i n Plant Physiology, Fourth Edition, b y F . B . Salisbur y an d Cleo n W . Ross , publishe d by Wadswort h Publishin g Company , Belmont, California , 94002 , U.S.A. , an d i n Journal o f Plant Physiology (Salisbury, 1991). Recen t study o f th e firs t an d second-leve l authoritie s (describe d in thi s chapter ) has le d no t onl y t o a somewhat differen t approac h but als o t o som e importan t modification s an d change s i n a fe w units and th e rule s for thei r use .

3

4 The

Basics

unify th e metri c syste m further , th e 9t h CGP M i n 194 8 instructe d th e CIP M t o study an d recommen d th e establishmen t o f a "practical system o f units of measurement suitabl e for adoption b y all signatories to the Metr e Convention " (se e Taylor , 1991). Thi s conferenc e als o laid dow n a set of principles fo r unit symbols and gav e a lis t o f unit s with special names . Si x base unit s were established i n 1954 , an d th e 11th CGP M i n 196 0 adopte d th e nam e Le Systeme International d'Unites (English : International Syste m o f Units) wit h th e internationa l abbreviatio n SI . Th e 11th CGPM also laid down rules fo r prefixes, derived an d supplementary units, and othe r matters. Thu s th e S I was born in 1960 , and subsequent meetings have added various amendments. Th e 14t h CGPM, in 1971, fo r example, added the mole to the original six base units , making a total o f seven bas e units in the SI , each with its own name and symbol , which i s th e sam e (wit h slight spellin g differences ) i n al l languages . The SI is currently by far the best measuremen t system humankind has been abl e t o develop. The purpos e o f thi s chapte r i s to presen t th e SI , especially a s it applies t o th e plant sciences . Th e informatio n presented her e come s fro m variou s sources. I t is convienent t o thin k o f thre e level s o f authority : Th e first , mos t primar y level, i s "Le Systeme International d'Unites (SI), 6 e Edition", French an d Englis h texts . Thi s is th e definitiv e publicatio n issue d i n 199 1 b y the Internationa l Bureau o f Weights and Measure s (BIPM) . Althoug h thi s publicatio n wa s prepared jointl y with th e National Physica l Laborator y i n th e Unite d Kingdom , some word s an d practice s follow Unite d State s rathe r tha n Britis h usage . I n general , this usag e (e.g. , mete r instead o f metre and lite r instea d of litre) i s closer t o the Europea n usag e than ar e the Britis h practices . Th e Unite d States translation o f this primary volume is listed in th e reference s t o thi s chapte r a s Taylo r (1991) ; i t i s virtually identica l t o th e version publishe d b y the BIP M except fo r a few small matters such as use of the do t instead o f the comm a a s the decima l marker. On e second leve l source o f authority is the IS O Standard s Handbook , Thir d Edition , publishe d i n 199 3 b y the Interna tional Organizatio n fo r Standardizatio n (ISO) i n Geneva , Switzerland . I t expand s upon th e rule s o f th e primar y source , an d thes e expansion s hav e influence d th e deliberations o f th e CGP M s o tha t som e recommendation s of th e IS O Standard s Handbook hav e become officia l S I rules. Anothe r second leve l sourc e o f authority is Special Publication (SP ) 811 of the Nationa l Institute of Standards and Technolo gy (NIST , formerl y the U.S . Nationa l Burea u o f Standards). S P 811 is the "Guid e for th e us e o f th e Internationa l Syste m o f Units (SI), " prepared b y Taylor (1995) . The third leve l o f authorit y include s th e man y publications suc h a s thi s on e tha t attempt to summarize , interpret , and condens e the SI for a give n field . (Se e many of th e bold-face d entries i n the lis t at the end of this chapter.) Th e rules presente d here are take n almos t exclusivel y from th e firs t tw o authority levels. 1. QUANTITIE S AND UNITS In scienc e i n genera l an d th e plan t science s i n particular , we dea l wit h physical quantities. T o communicate these physical quantities, we use three kinds of symbols: a symbol for th e physica l quantity, a symbol for a numerical value (i.e., a number),

The International System of Units (SI Units) 5 and a symbo l fo r a unit. Fo r example , i f we want t o communicat e th e lengt h o f some object , w e can write : l = 5.6 7 m If thi s notatio n i s to be a meaningful form o f communication, thos e o f us who want to communicat e mus t agre e tha t th e symbo l for lengt h is l, that w e will use Arabic numerals, an d tha t th e mete r (m ) represents a standard unit of length; namely , th e length o f th e pat h travelle d b y light i n vacuum during a time interval o f 1/29 9 79 2 458 o f a second . O f course , fo r practica l purposes , mos t o f u s wil l trus t th e manufacturers o f mete r stick s an d othe r measurin g devices , assumin g tha t thos e manufacturers accuratel y follo w a reliable standard when they create th e measurin g instruments. Th e variou s nation s hav e bureau s t o insur e thi s accurac y (i n th e United States , Th e Nationa l Institut e o f Standards an d Technology) , an d a s note d above, th e ultimat e authorit y for standards goes bac k to the CGP M an d the BIPM . Remember tha t th e uni t represent s a number . Th e physica l quantit y i s th e numerical valu e multiplie d b y th e unit . Thus , th e uni t i s subjec t t o algebrai c manipulations. Fo r example , th e numerica l value can be thought o f as the rati o of the physica l quantity to th e unit ; i n the abov e example : l/ m = 5.67 . Thi s notatio n is particularly usefu l i n graph s and i n th e heading s o f columns in tables . Note that th e symbol for the physical quantity (length in the example) is written in italic or slanted type (underlined if italic type is not available) , an d th e symbol for the uni t i s written i n roman (upright ) type. Thi s rul e (listed agai n in Table 4 , #17 ) should b e followe d wit h Greek symbol s as well as those fro m th e Roma n alphabet . 2. LE SYSTEME INTERNATIONAL

D'UNITES (SI)

The SI is a so-called coherent unit system, in which the equation s between numerica l values hav e exactl y th e sam e for m (includin g the numerica l factors ) a s th e corre sponding equation s betwee n th e quantities . Thi s i s achieved b y defining unit s fo r the bas e quantitie s (th e base units), and then derivin g further unit s fro m thes e bas e units based upo n th e equations betwee n th e quantitites. Fo r example, th e equatio n for spee d (v ) shows speed a s being equal t o th e incrementa l change i n distance (dl ) divided b y the incrementa l chang e i n time (dt) : v = dl/dt. Thu s th e uni t for spee d is th e mete r pe r second : m/s . Therefore , th e S I include s base units an d derived units. I n additio n ther e ar e tw o supplementary units, th e radia n (rad , fo r plan e angle) an d th e steradia n (sr , fo r solid angle) . The seve n bas e unit s o f th e S I ar e th e meter (length ; metre i s als o used , especially i n Britai n an d France) , kilogram (mass), second (time) , ampere (electri c current), kelvin (thermodynami c temperature) , candela (luminou s intensity) , an d mole (amoun t o f substance). Thes e units are show n with their symbol s in Table 1 . Actually, i t i s possible b y combining th e unit s of space (length , area , an d volume ) with those of mass, time, an d temperatur e t o deriv e unit s of any physical quantity . The basi c uni t o f lengt h i s th e meter (m) , whic h wa s originall y define d a s equivalent t o th e lengt h of a bar preserve d i n Sevres, France; i n 196 0 i t was defined as th e lengt h equa l t o 1 650 763.73 wave lengths in vacuum o f the radiatio n corre sponding t o th e transitio n between th e level s 2p10 an d 5d 5 of the krypton-8 6 atom.

6 The

Basics

In 1983 , agai n i n response t o advancin g technology, the mete r was redefined as th e distance ligh t travel s i n a vacuu m during a tim e interva l o f 1/29 9 79 2 45 8 o f a second. Table 1 . Th e Seve n Bas e Units Quantity

Unit

Symbol

Length (l )

meter

m

Mass (not weight ) (m a)

kilograma

kg

Time (t )

second

s

Electric curren t (I )

ampere

A

Thermodynamic temperatur e (T )

kelvin

K (not °K )

Luminous intensit y (I )

candelab

cd

Amount o f substance (n , Q )

c

mole

mol

a

For historical reasons, the kilogram is the SI base unit rather than the gram. It is a unit of mass rather than weight. Although weight is an acceptable synonym for mass, plant scientists should be careful to use mass instead of weight whenever appropriate—which is most of the time. (Note that the quantity mass is symbolized with italic m, which is not to be confused with roman m for meter. See ISO Standards Handbook, 1993.) As a unit of luminous intensity, the candela was traditionally based on the sensitivity of the human eye; we know of no application in plant physiology. The lux (lx) is a measure of illuminance based on the candela (1 1x = 1 cd. sr. m-2 ); it has been widely used in plant science but should be avoided. c

The mole should always be used to report the amount of a pure substance, and in such cases the type of substance must be specified. To report the amount of a mixture or of an unknown substance, mass must be used.

For historica l reasons , th e gra m is not the S I base unit for mass. Th e kilogram is th e onl y bas e uni t wit h a prefix . I t i s equa l t o th e mas s o f th e internationa l prototype o f th e kilogram , mad e o f platinum-iridium , kept a t th e BIP M unde r conditions specifie d b y the firs t CGP M i n 1889 . Not e tha t weight i s technically a measure o f th e force produce d b y gravity, whereas the kilogra m is a uni t o f mass. Mass i s a fundamenta l quantity that doe s no t chang e with the forc e of gravity (for example, wit h location) . Th e weigh t o f objects , o n th e othe r hand , i s abou t 1 percent les s a t th e equato r tha n a t th e pole s an d i s 82 percent les s o n th e moon . Thus i t is technically incorrec t t o use the word weight in conjunction with the uni t kilogram. Th e prope r uni t for weight is the newton . (O n earth, the weight of a 10 kg mass is about 98 newtons.) Although in many technical fields and i n everyday us e the term "weight* is considered as an acceptable synonym for "mass* plant scientists should use the term "mass* whenever it is appropriate. A balanc e balances th e mas s o f a n unknow n object agains t a define d mass; hence, a balance measure s true mass. Al l balances depend upon an accelerationa l force fo r thei r function , bu t th e magnitud e of th e accelerationa l forc e doe s no t affect th e reading . Unfortunately , the magnitud e of accelerational force doe s affec t the measuremen t o f mas s o n electroni c "balances " becaus e the y ar e reall y scale s

The International System of Units (SI Units) 1 that measur e weight . Thi s i s usually no t a seriou s proble m becaus e th e forc e of gravity is constant fo r a given location, and electronic balance s an d spring scales are calibrated with a standard se t o f objects o f known mass. All object s wit h a mas s als o have a volume and thus displace som e air , which has a densit y o f 1.20 5 k g m" 3 (standard atmospheri c pressure , dr y air , 2 0 °C) . A correction fo r this volume displacemen t woul d be necessary in some situations (fo r example, measurin g th e mas s of a heliu m balloon!) , bu t mos t plan t tissue s hav e a density simila r t o tha t o f water (1,00 0 kg m-3), s o the correctio n i s only about 0. 1 percent. Note that a quantity of substance ca n be expressed either i n terms of its mass or the numbe r o f particle s o f whic h i t i s composed : "Th e mole i s th e amoun t o f substance o f a system tha t contain s a s many elementary entities as there are atom s in 0.01 2 kilogra m o f carbo n 12 . Whe n th e mol e i s used , th e elementar y entitie s must b e specifie d an d ma y be atoms, molecules , ions , electrons , othe r particles , o r specified group s o f suc h particles " (Taylor , 1991) . Plan t physiologist s an d other s include photon s amon g th e particle s tha t ca n be expressed i n moles, but not e that the einstei n ( a mol e o f photons) i s not a n S I unit an d shoul d no t b e used . Not e that 1 mol o f a substance contain s Avogadro's number of particles (no w defined a s the numbe r o f atoms i n 0.012 k g of carbon 1 2 6.02204 5 x 10 23 particles) . Following variou s astronomica l definition s of the second (e.g. , 1/8 6 40 0 of th e mean sola r day), the secon d was defined i n 196 7 a s the duratio n o f 9 19 2 631 770 periods o f the radiatio n correspondin g t o th e transition betwee n th e tw o hyperfine levels of the groun d state of the cesium-133 atom . Althoug h the minute, hour, day, week, month, an d year are not officiall y par t of SI, plant physiologists will continu e to us e them whe n appropriate . The ampere is defined as that constan t current require d to produce, in vacuum, a forc e o f 2 x 10- 7 newton s per mete r o f length between two parallel conductor s of infinite lengt h and 1 meter apart . Becaus e force (the newton) is defined in terms of length, mass , and tim e (se e Tabl e 2) , current coul d also be defined i n those terms . The kelvin was define d b y the CGP M i n 196 7 a s th e fractio n 1/273.1 6 o f th e thermodynamic temperature o f th e tripl e poin t o f water. Tha t sam e CGP M als o adopted th e nam e kelvin (symbo l K ) t o b e use d instea d o f degree Kelvin (symbo l °K). I n addition t o the physical quantity thermodynamic temperature (symbo l T, unit K), us e is also mad e o f Celsius temperatur e (symbo l t, unit °C) , where t = T - T 0 and T 0 = 273.1 5 K by definition. A n interva l or differenc e o f Celsius temperatur e can be expressed i n kelvin s a s well as in degrees Celsius . Luminous intensit y (th e candela) wa s define d i n term s o f th e ligh t intensit y perceived b y the huma n eye as compared with the intensity of freezing platinum, but in 197 9 i t was redefined a s monochromatic radiation with a frequency o f 540 x 10 12 hertz and a radiant intensit y of 1/68 3 wat t per steradian . Th e watt (unit for power) also combine s length , mass , and time. Thus , although the S I recognizes seve n base units, only the unit s of length, mass, time, temperature, and numbe r (th e mole) ar e truly basic in that the y are no t derive d from an y other units—and temperature could be derive d fro m th e firs t three .

8 The

Basics

Because th e candel a an d it s derivative s wer e base d o n th e sensitivit y o f th e human eye, and plan t sensitivitie s ma y be very different (dependin g on the pigmen t involved), the candel a an d it s derivatives (e.g. , the lux ) should not b e used by plant scientists. Thi s i s true i n spite o f the mor e recen t definitio n based o n monochro matic light . Whil e th e candel a i s o f valu e t o engineer s wh o ar e concerne d wit h artificial lighting for human beings, other measure s of radiation can be derived fro m power (th e watt) pe r uni t are a ( W m- 2) or the numbe r (moles) of photons pe r uni t area time s uni t tim e (usuall y [umol m-2 s-1). Thes e unit s should b e use d b y plant scientists. I n either case , wav e lengths or frequencie s must be specified. Table 2 list s th e prefixe s that ar e use d i n th e Internationa l Syste m of Units . Some third-leve l publication s hav e suggested tha t fou r o f th e prefixe s were "non preferred": centi , deci, hecto, and deka. Althoug h the y were commonly used i n the metric system, it was suggested that the y should be avoided when it is convenient to use th e others . Th e first-leve l an d second-leve l sources , however , mak e n o suc h distinction abou t bein g preferre d o r non-preferred . I n man y cases , usin g thos e prefixes i s convenient an d lead s t o clarity . I n othe r cases , i t i s logical t o us e onl y prefixes tha t diffe r b y a factor of 1 000 (103). Table 2. SI Prefixesa (multiples and submultiples) Factor

Prefix

da

(10)

deci

d

hecto

h

(102)

centi

c

kilo

k

(10 )

milli

m

mega

M

micro

u

giga

G

(106) 9

Prefix

Symbol

deka

tera

T

peta

P

3

(10 )

Symbol

nano

n

12

pico

1S

femto

P f

18

(10 ) (10 )

Factor

(10-1) (10-2) (10-3) 6

(10- ) (10-9) (10-12) (10-15)

exa

E

(10 )

atto

a

(10-18)

zetta

Z

(1021)

zepto

z

yotta

Y

(1024)

yocto

y

(10-21) 24

(10- )

' Th e firs t syllabl e of every prefix is accented t o assure that the prefix will retai n its identity.

Table 3 show s som e importan t S I derive d unit s with specia l name s tha t ar e derived fro m th e bas e unit s and ar e o f value to plan t scientists. (Se e Taylor , 1991 , for complet e lists. ) Not e tha t th e standar d acceleratio n du e t o gravit y i s a n experimentally determined unit, and th e unifie d atomi c mass is an arbitrar y unit.

The International System of Units (SI Units) 9 Table 3. Derived Units of Interest to Plant Physiologists Unit Nam e Symbol Quantity (symbol) a Area (A )

square meter

m2 3

Definition m.m

Volume (V )

cubic mete r

m

m.m.m

Speed or velocity (v )

meters pe r secon d

m.s-1

m.s-1

Force (F )

newton

N

kg.m.s-2

Energy (E) , work (W), hea t (Q )

joule

J

N.m (m 2.kg.s-2)

Power (P )

watt

W

J.s-1 (m 2.kg.s-3)

Pressure (p )

pascal

Pa

N.m-2 (kg.s-2.m-1)

Hz

cycle s-1

Frequency (v , Gree k nu ) hertz Electric charg e (Q )

coulomb

C

A.s

Electric potentia l (V , )

volt

V

W.A-1 (J.A- 1.s-1; J.C-1)

Electric resistanc e (R )

ohm

ft

V.A-1

Electric capacitance (C )

farad

F

A.v-1 ( - 1) c.v.1

Concentration (c )

moles per cubi c meter

mol.m-3

mol.m-3

Irradiance (energy : E )

watts per squar e meter

W.m-2

J.s-1.m-2

Irradiance (mole s of photons)

moles per squar e meter secon d

mol.m-2.s-1

mol.m- 2.s-1

Spectral irradiance (moles o f photons )

moles pe r squar e meter secon d nano meter

mol.m-2 .S-1 .nm-1

mol.m-2.s-1. nm-1

Magnetic field strengt h (H)

amperes pe r mete r

A.m-1

A.m-1

Activity (o f radioactiv e source: A )

becquerel

Bq

s-1

Standard acceleratio n due t o gravity

standard acceleratio n gn due t o gravity

9.806 6 5 m s-2

Unified atomi c mass unit

Unified atomi c mass uni t

1/12 o f mass of 12 C

Electric conductanc e (G ) Siemens

a

S

u

Quantit y symbol s ar e fro m IS O Standard s Handbook , 1993 . Ther e ar e man y varizitions o f suc h symbols .

Technically, velocity i s a vector quantit y requirin g specification o f a magnitud e (speed ) an d a direction, bu t mag nitude i s most importan t i n plan t science .

10 Th

e Basics

Table 4 summarizes th e styl e conventions tha t gover n the us e of S I units an d that ar e o f interes t t o plan t scientists . Mos t o f thes e rule s ar e fro m th e primary source o f authority : L e System e International d'Unite s (SI), 6 e Edition (o r th e American Englis h equivalent: Taylor , 1991), bu t man y rely on the second-level IS O Standards Handbook an d NIS T Specia l Publicatio n 811 (Taylor, 1995) . A few are recommendations fro m third-leve l publications ; these ar e noted her e and discussed further i n the tex t and in relation t o Table s 5 and 6. Table 4. Summary of SI Style Conventions (Rules) Names of units and prefixes 1. Uni t name s begi n i n lowercase, excep t a t th e beginnin g of a sentence o r i n titles or heading s in which al l mai n words ar e capitalized ; tha t is , conventional grammatica l rule s appl y t o names. Units name d afte r individuals a als o begi n i n lowercase . (Th e "degre e Celsius " migh t appea r to b e a n exception , bu t "degree " begin s i n lowercas e an d i s modifie d b y "Celsius, " th e nam e of a n individual . Us e o f "degrees centigrade" i s obsolete.) 2. Appl y only one prefix t o a unit name (e.g. , nm , not mum) . Th e prefi x an d unit name ar e joine d without a hyphe n o r spac e between . I n thre e cases , th e fina l vowe l o f th e prefi x is dropped : megohm, kilohm , an d hectare . Prefixe s ar e adde d t o "gram, " no t t o th e bas e uni t "kilo gram." Prefixe d ar e neve r use d b y themselves . 3. I f a compound uni t involving division is spelled out , th e word per i s used (no t a slash or solidus , except i n table s i n which space ma y b e limited) . Onl y one per i s permitted i n a writte n uni t name (se e Rul e 3 0 below). 4. I f a compoun d uni t involvin g multiplicatio n i s spelle d out , th e us e o f a hyphe n i s usually unnecessary, bu t i t ca n b e use d fo r clarit y (e.g., newto n mete r o r newton-meter) . Th e multi plication (product ) do t (• ) shoul d no t b e used when unit names ar e spelle d out . 5. Plural s of uni t name s ar e forme d b y adding a n "s, " excep t tha t hertz , lux , and Siemen s remain unchanged, an d henr y become s henries . 6. Name s o f unit s are plura l fo r numerica l values greater tha n 1 , equal t o 0 , or les s tha n -1 . Al l other value s tak e th e singula r form o f th e uni t name . Examples : 10 0 meters , 1. 1 meters , 0 degrees Celsius , - 4 degrees Celsius , 0.5 meter, -0. 2 degre e Celsius , - 1 degree Celsius , 0. 5 liter. 7. NIS T S P 811 (Taylor , 1995 ) recommend s tha t writte n name s o f units be avoide d mos t o f th e time; unit symbols shoul d b e used instead . I t is appropriate, however , to use a written name th e first tim e th e uni t appear s i n a tex t i f it i s felt tha t reader s migh t not b e familia r wit h the unit . Symbols for units 8. Uni t symbol s shoul d b e though t o f as mathematica l entities : Th e physica l quantit y equals th e numeral multiplie d b y th e valu e represented b y the uni t symbol . Hence , with fe w exceptions (see Rule s 7 and 15) , symbol s are use d whe n units are use d i n conjunction with numerals. 9. Writte n symbol s are neve r mad e plura l (that is , by addition o f "s") . 10. A symbo l i s not followe d b y a perio d excep t a t th e en d o f a sentence . 11. Symbol s fo r unit s named afte r individualsa have th e first letter capitalized , but th e nam e o f th e unit i s written i n lowercas e (se e rul e 1) . Othe r symbol s ar e no t capitalize d excep t tha t th e second leve l authorities recommen d a capita l L instea d o f a lowe r cas e 1 as th e symbo l fo r th e liter t o avoi d confusio n with the numera l one (1) . Bot h L and 1 are recognize d b y the primar y authority a s symbols fo r th e liter . Th e capita l L is recommended here . 12. Symbol s fo r prefixe s greate r tha n kil o ar e capitalized ; kil o and al l others ar e lowercase . I t i s important t o follo w thi s rule because some letter s for prefixe s ar e th e sam e as some symbols or another prefix : G fo r gig a an d g for gram ; K fo r kelvi n an d k fo r kilo ; M fo r meg a an d m fo r milli an d fo r meter ; N fo r newto n an d n fo r nano; an d T fo r ter a an d t fo r metri c ton . Continued

The International System o f Units (S I Units) 1

1

Table 4. Summary of SI Style Conventions (Rules) (continued) 13. Us e numerica l superscript s (2 and 3 ) to indicat e squares an d cubes; d o not us e sq., cu. , or c. I t is also better, when uni t name s ar e writte n out , t o us e the for m "secon d squared " rathe r tha n "square second" unless volume o r are a ar e being discussed: "squar e meter, " "cubi c meter." 14. Exponent s als o appl y t o th e prefi x attache d t o a unit name; th e multipl e or submultipl e uni t is

treated as a single entity. Thus nm3 is the same as 10-18 m3.

15. Third-leve l sources an d Englis h styl e manual s recommend tha t sentence s shoul d no t begi n with numerals. Becaus e a unit symbol is always proceeded wit h a number (numeral), a sentence can never begi n wit h a uni t name o r symbol . Wheneve r possible , a writer shoul d recas t a sentenc e so it does not begi n with a numeral; if that can't b e done, th e numbe r and unit name shoul d b e spelled out . 16. Compoun d symbol s forme d b y multiplication may contain a produc t do t (• ) t o indicat e multiplication; internationa l rule s sa y tha t thi s ma y b e replace d wit h a perio d o r a space . I n th e United States, the produc t do t i s recommended. Compoun d symbol s formed by division can use a slas h (/) , a horizonta l lin e with units above an d below , or b e indicate d by negative exponents ; e.g., umol. m .s-1, umol.mol- 1 , etc . I n n o cas e shoul d symbol s b e ru n togethe r (e.g. , Wm-2). 17. Becaus e compoun d uni t symbol s ar e mathematica l entities , the y mus t no t includ e nonsymbo l words o r abbreviations . Thi s i s not tru e of unit names without numerals. Thu s an author mus t avoid " umol CO2 (mo l o f air)- 1" bu t ca n write: "Dat a ar e presente d a s micromole s o f CO 2 per mol e o f air ( umol.mol- 1)." (Se e discussio n i n the text. ) 18. D o no t mi x symbols an d spelled-ou t uni t name s (e.g. , W per squar e meter) , an d never mi x SI units or thei r accepte d relative s (e.g. , liter, minute, hour , day , plane angle in degrees) wit h units of another system suc h as the CG S or th e Englis h system (e.g. , mile s per liter , kg ft-3, o r gram s per ounc e fo r th e quantit y o f fat i n a food) . 19. Th e percen t symbo l (% ) i s an acceptabl e uni t for us e with th e SI : % = 0.01 . Whe n used , a space i s left betwee n th e symbo l % an d th e numbe r b y which it i s multiplied: X = 25 % = 2 5 x 0.0 1 = 0.25 . Rathe r tha n usin g such terms as "percentage b y volume" (meaningless becaus e % i s simply a number) , a recommende d approac h i s to presen t dat a a s mL/L, umol/mol , g/kg , mol/L, mol/kg , etc . (Taylor , 1995). 20. Uni t symbol s ar e printe d i n roman typ e (uprigh t letters); italic letters (slanted ) ar e reserve d for quantity symbols , suc h a s A fo r area , m fo r mass , t fo r time , and fo r water potential . Fo r typewriting or longhand , underlinin g may be use d a s a substitute fo r italics . Accordin g t o thi s rule, th e Gree k mu , u , whe n use d a s the prefi x symbol fo r micro , should b e printe d i n roma n type (no t i n italics). Numerals, often with Symbols 21. A spac e i s lef t betwee n th e las t digi t o f a numera l an d it s uni t symbol . A produc t do t (•) , space, o r slas h (/ ) i s use d betwee n uni t symbol s when mor e tha n on e i s used ; se e rul e 16 . Exceptions ar e th e degree , minute, and second symbol s for angles or latitude s (e.g., 30 ° north) . Note tha t th e degre e Celsiu s (°C ) i s a singl e uni t symbo l (n o spac e betwee n an d C ) tha t should als o b e proceede d b y a space . I t i s incorrect t o us e 1 2 t o 2 5 ° C (tha t is , to us e ° without C) ; correc t form s are: 1 2 °C to 2 5 °C, (12 to 25) °C , or 12-2 5 C . 22. Whe n a quantity is used i n an adjectiva l sense, Englis h rule s of grammar suggest tha t a hyphe n should b e used betwee n the numera l and the uni t name: a five-hundred-watt lamp . Bu t when unit symbols ar e used , the hyphe n shoul d b e omitted: a 50 0 W lamp (becaus e th e symbo l i s a mathematical entity , an d th e hyphe n coul d b e mistake n for a minu s sign). 23. I n th e Unite d States , th e perio d i s used a s the decima l marker although some countrie s (e.g., France, Germany , Grea t Britain ) use a comma o r a raised period . Continued

12 Th

e Basics

Table 4. Summary of SI Style Conventions (Rules) (continued) 24. T o avoi d confusio n (becaus e some countrie s us e a comma a s a decimal marker), a space shoul d be used instea d o f a comma t o group numerals into three-digit groups; this rule may be followed to th e righ t a s wel l a s t o th e lef t o f th e decima l marker . Omissio n o f th e spac e i s preferre d when ther e ar e onl y four digits , unless th e numera l i s in a colum n with others tha t hav e mor e than fou r digits . (I n spit e o f thi s rule , man y journals tha t consistentl y us e a perio d a s th e decimal marke r als o us e the comm a t o grou p numeral s int o three-digit groups. ) 25. Decima l fraction s are preferre d t o commo n fractions . 26. Decima l value s les s tha n on e hav e a zero to th e lef t o f the decima l (e.g. , 0.2 m). 27. Multiple s an d submultiple s ar e generall y selecte d s o tha t th e numera l coefficien t ha s a valu e between 0. 1 and 1000. Exception s occu r when the differences between number s being compare d are extrem e (e.g. , 150 0 m o f 2 m m wire) , an d fo r comparison , especiall y i n tables , simila r quantities shoul d us e th e sam e unit , even i f the value s fal l outsid e thi s range . 28. Wit h numerals , d o no t substitut e th e produc t do t (• ) fo r a multiplicatio n sign (x) . (E.g. , us e 2 x 2 , not 2.2. ) The denominator 29. Fo r a compound uni t tha t i s a quotient , us e "per" t o for m th e nam e (e.g. , meters pe r second ) and a slas h (/ ; solidus) t o for m th e symbol , with no spac e befor e o r afte r th e slas h (e.g. , m/s) . Compound unit s may be written wit h negative exponent s (e.g. , m.s-1 o r m s- 1). 30. D o no t us e tw o o r mor e "pers " o r slashe s i n the sam e expressio n becaus e the y ar e ambiguou s (see Rul e 3) ; negativ e exponent s avoi d thi s problem : J.K-1 .mol- 1 (no t J/K/mol) ; J/K.mo l i s acceptable because all symbols t o th e righ t of the slas h belong t o th e denominator . 31. Man y third-leve l source s suggest tha t th e denominato r shoul d no t b e a multipl e or submultiple of a n S I base uni t (e.g.,uN.m- 2 bu t no t N.um-2 ). (Bu t se e discussio n i n the text. ) aIndividuals afte r who m unit s ar e name d include : Antoin e Henr i Becquere l (France , 1852-1908) , Ander s Celsiu s (Sweden, 1701-1744) , Charle s Augusti n d e Coulom b (France , 1736-1806) , Michae l Farada y (England , 1791-1867) , Heinrich Rudol f Hert z (Germany , 1857-1894) , Jame s Prescot t Joul e (England , 1818-1889) , Lor d Willia m Thomso n Kelvin (Scotland, 1824-1907) , Sir Isaac Newton (England, 1643-1727), Geor g Simon Ohm (Germany, 1787-1854), Blaise Pascal (France , 1623-1662) , Si r Willia m Siemens (Germany , Great Britain , 1823-1883), Coun t Allessandr o Giusepp e Antonio Anastasi o Volt a (Italy , 1745-1827) , an d James Watt (Scotland, England, 1736-1819).

The CIP M recognized i n 196 9 tha t users of SI will also wish t o emplo y with i t certain unit s that ar e no t par t o f it , bu t tha t ar e importan t an d ar e widel y used. These unit s (along with the unifie d atomi c mass unit and the standard acceleration due t o gravity) , ar e show n in Table 5 . Not e tha t a goal in settin g up th e International Syste m of Units was to produc e a coherent system , as noted above , a system in whic h derive d unit s ar e variou s combination s o f th e bas e unit s withou t th e necessity o f including numerical multiplication factors. Al l of the unit s in Table 5 do requir e th e us e o f suc h factors , an d henc e the y los e th e advantage s o f th e coherence o f SI units . I t was recommended that thei r us e be restricted t o specia l cases. I t i s clear, however , that plant scientists will use th e minute , hour, and day (not to mention the week, month, and year) without hesitation in reporting methods and results . Th e liter is also a much more convient unit for plant scientists than the cubic meter, which i s th e officia l S I unit of volume. Thus , we can b e thankfu l fo r the CIPM' s decision s in 196 9 and fo r Table 5!

The International System o f Units (S I Units) 1

3

Table 5. Some Units used with the SI but not Officially Part of SIa Name

Symbol

Value i n SI units

minute

min

1 min = 60 s

hour

h

1 h = 6 0 min = 3600 s

day

d

1 d = 2 4 h = 8 6 400 s

degree

o

1° = ( /180 ) ra d

minute

f

1' = (1/60) ° = ( /1 0 800) rad

second

"

1" = (1/60) ' = ( /64 8 000) rad

liter (litre)

L (l)

1 L = 1 dm3 = 10- 3 m 3

metric ton (tonne)

t

1 t = 10 3 kg

unified atomi c mass unit b

u

1 u = (1/12 ) of the mass of an atom of the nuclid e 12 C

standard acceleration g due t o gravit y c

n

9.80

6 65 m.s-2

a

Becaus e thes e units must be multiplied by a factor t o mak e the m equivalen t t o SI units, the y are no t coheren t in the sense of othe r SI units.

The actua l value of th e unifie d atomi c mass uni t in SI unit s must be determined by experimentation. A t presen t it is considered consideredto to be: u = 1.66 0 540 2(10) 2( x 10- 27 kg . Th e uncertainty of the last tw o figures, a t the level of one standard deviation, i s shown i n parentheses. c

Thi s valu e was confirmed in 191 3 b y the 5t h CGPM . It s symbol , g n, shoul d b e use d instea d o f th e man y symbols currently used t o indicat e one acceleratio n due t o gravity at the earth's surface (e.g. , g , g, G, G , Xg , etc.).

Table 6 includes som e unit s that were use d with the metric syste m but tha t th e CIPM recommend s shoul d no t b e use d wit h the SI . A fe w of these units continu e to b e in wide use among plan t scientists . 3. SOME SPECIAL CONSIDERATIONS Although mos t o f th e rule s i n Table 4 are explaine d adequatel y in th e table , a few of the m a s well as some o f the unit s in Tables 5 and 6 are worthy of discussion . A. Language Conventions with Si-Unit Names and Symbols.2 Writte n ou t names fo r the unit s follow the rules of grammar (English or other language) , whereas th e uni t symbols shoul d b e though t o f a s mathematica l entitie s b y which th e preceeding numera l i s multiplied. Fo r example , unit names begin with a lowercase letter unles s grammatica l rule s cal l fo r uppercas e (i.e. , a t th e beginnin g o f a sentence an d i n titles) , bu t th e uppe r o r lowercas e o f symbols mus t neve r b e changed regardles s o f where the y appear. I n English, names ar e often mad e plural

2

Rule s in Table 4 that bea r on thi s discussio n are : 1, 7, 8, 15, 17, & 22.

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by addition o f s, but S I symbols never are . Number s (usuall y written out ) followe d by uni t name s use d i n an adjectiva l sens e can be connecte d wit h a hyphe n (e.g. , a fifty-watt lamp ) bu t th e hyphe n i s not use d wit h symbol s (a 50 W lamp). Becaus e of the mathematica l natur e o f symbols, it is desirable t o us e them instea d o f names . Of course the nam e ca n be used th e firs t tim e i t appears if the reader migh t not b e familiar wit h th e uni t o r it s symbol. In som e language s i t i s no t uncommo n fo r a numera l t o begi n a sentence ; i n English thi s should b e avoided, preferabl y by recasting th e sentence, but if necessar y by writing out th e numera l an d it s unit name . Table 6. Some Discarded Metric Units Discarded Metric Unit

Acceptable SI Unit

micron (u )

micrometer ( um )

millimicron (mu ) angstroma (A)

0.1 nanometer (nm)

nanometer (nm)

bara (bar )

0.1 megapascal (MPa); 100 kilopascal (kPa)

calorie (cal)

4.1842 joule (J)

degree centigrad e (°C)

degree Celsiu s (°C )

hectarea (ha )

10 000 m2 or 0.01 km 2 mole of photons or quant a (mol)

einstein (E ) dalton (Da )

unified atomi c mass unit (u ) (see Tabl e 5)

standard "gravity " (g, g, G, G, xg , etc. )

standard acceleration due to gravity (g n)

molar solution (M)

mol-L-1 (kmol m-3)

molal solution (m )

mol-kg-1

parts per millio n (ppm)

mg.kg-1 {umol.mol-1 (e.g., CO 2 i n air) (Use k g for mixe d substances and mo l fo r pure substances and gases. ) 1000 mm 3.m-3 (volume ; e.g., liquids) -1 ug.kg-1 nmol.mol-1 mm3.m-3 (volume ; e.g., liquids)

parts per billio n (ppb )

aIn vie w of existin g practice i n certai n fields , th e CIPM (1978 ) considered tha t these units could b e use d with the SI temporarily although they should no t be introduced wher e they are no t use d a t present.

Because name s follo w grammatica l rules , i t i s acceptabl e t o us e the m i n conjunction wit h othe r terms , bu t suc h term s mus t not b e include d wit h S I units : "Photon flu x wa s measure d a s mole s o f photon s i n th e photosyntheticall y activ e range (40 0 t o 70 0 nm ) pe r squar e mete r secon d (umol.m-2 .s-1 )." "Dat a ar e presented a s milligram s of protei n pe r gra m of fres h tissu e (mg/g). " Or : "Protei n

The International System o f Units (S I Units) 1

5

data ar e presente d o n a fresh-mass basis (mg.kg- 1)." Thi s rule i s often overlooke d by plan t physiologists , wh o eve n sometime s construc t meaningles s symbol s t o present thei r data : mg/gf w (meanin g milligrams per gram of fresh weight) or mg (kg fresh mass)- 1. Th e rul e was discussed b y Downs (1988) and perhap s in othe r thir d level source s o f which I am not aware , but i t has otherwise been largel y overlooked by plant physiologists. Th e rule is emphasized, however, by the second-level authorities (ISO Standard s Handbook , 1993 ; NIS T S P 811 , Taylor , 1995) . Plan t scientist s should improv e the rigo r of their presentation s b y adhering to this rule . B. Space Between Numerals and Units and Within Compound Units. Fo r some unknow n reaso n i t ha s becom e increasingl y commo n t o omi t th e spac e between a numeral and the unit that follows (e.g. , a 50mL flask) . I n the worst cases, the spac e o r produc t do t i s omitted betwee n symbol s in a multipl e unit, creatin g new symbol s tha t hav e n o meanin g (e.g. , Wm- 2, umolm-2S- 1, etc.) . Thi s practic e breaks Rule s 16 , 19 , and 2 1 i n Tabl e 4 , an d leavin g ou t th e spac e ca n confus e readers. Us e o f th e produc t do t i s highl y recommende d i n th e Unite d State s (Taylor, 1995) , but plan t scientists hav e used it only infrequently. It s consistent us e would remove any ambiguity from multipl e units and would overcome the tendency to run units together. C. Italics for Quantity Symbols, Roman for Unit Symbols. Thi s simple practice is stated i n Rul e 20 , Table 4 , but man y plan t scientists seem t o b e unawar e of it . Remember tha t unit symbols are printed in roman type (upright letters); italic letters (slanted) ar e reserve d fo r quantit y symbols, such a s A fo r area , m fo r mass , t fo r time, and 7 fo r water potential. Fo r typewriting or longhand, underlining may be used as a substitute for italics. Accordin g to this rule, the Greek mu , u , whe n used as the prefi x symbol for micro, should be printed in roman (i.e., upright) type whenever possible . Unfortunately , not all word processors allow this. (Not e that Greek , Roman, or eve n Cyrilli c alphabets ca n be printed in either roma n or italic type). D. Only One per or Slash in a Multiple Unit. Thi s is another simple rule that plant scientist s shoul d appl y more widel y (Rul e 30, Table 4) : D o no t us e tw o or more "pers " o r slashe s i n th e sam e expressio n becaus e the y ar e ambiguous . Negative exponent s avoi d thi s problem : J-K-1.mol- 1 (not J/K/mol) ; J/K.mol i s acceptable becaus e al l symbols to th e right of the slash belong to the denominator. I f this is written out, i t becomes: joule s per kelvi n mole. E. Only Base Units in Denominators. A s note d i n Rul e 31 , Tabl e 4 , man y third-level source s sugges t tha t th e denominato r shoul d no t b e a multipl e o r submultiple o f a n S I bas e uni t (e.g. , uN.m- 2 bu t no t N.um- 2). A s edito r o f Journal of Plan t Physiolog y during the pas t si x years, I have found thi s rul e t o b e the mos t difficul t t o enforce . I t goe s against much tradition and sometime s seem s illogical an d unreasonable . Fo r example , authors hav e long reported amount s or concentrations o f metabolites, hormones, and other compounds as ug/mg, nmol/mL, etc. I t ma y seem t o g o against one's intuition to us e the equivalent s of thos e tw o examples: g/kg , umol/ L (or , using "true" SI units: mmol/m-3 ). Now I learn tha t th e rul e of onl y base unit s i n denominator s is recommended solely i n third-leve l sources bu t i s no t a n officia l S I rul e an d i s no t i n th e IS O Standards Handbook or NIST SP 811 (Taylor, 1995), which are second-level sources with virtually as much authority as the primary SI publication. I t is not necessar y to

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adhere t o ever y suggestio n pu t fort h i n third-leve l publications . Thus , I will n o longer tr y to enforc e the rul e in my editing. Having sai d that , I will nevertheless mak e an argumen t (third level! ) tha t th e rule (suggestion , at least ) can , in many cases, be quite logical and helpful. Us e of a single denominator fo r a given quantity by everyone in the fiel d allow s us to thin k about th e variou s quantitie s withou t th e necessit y o f mentally converting the m t o our familia r range, differen t perhap s fro m tha t o f th e autho r w e ar e reading . O f course, t o take advantag e of this rule, those within the field mus t agree t o form new habits. Fo r example , photosynthesis rate s were previously expressed on the basis of CO2 uptak e (a s milligrams or moles ) per squar e decimete r o f leaf surface, perhaps because a square decimete r seeme d t o be an area simila r to the are a o f real leaves . Most workers now express mos t parameters relatin g t o photosynthesi s on the basis of a square meter, a s suggested by this rule. Afte r all , few real leaves are exactl y 1.0 dm2 o r exactl y 1. 0 m 2 i n area . (Doe s a banan a lea f approac h 1. 0 m 2?) An d irradiance i s commonly expressed o n th e basi s of a square meter: umol.m- 2.s-1 o r W.m-2. Whe n everythin g i s expresse d o n th e sam e basi s (m- 2), comparison s ar e much easier. In spit e o f th e tradition s note d above , unit s fo r quantitie s o f mas s can easil y follow th e rule . Wh y express the amoun t of growth regulator in a tissue sample as 8.5 pg mg- 1 when i t i s just as eas y to writ e 8.5 u g kg- 1? A kilogra m is a relativel y large amount o f tissue , but i t is easy enough to visualize. Th e researcher probabl y didn't us e a 1. 0 mg sample of tissue an y more than he or she used a 1. 0 kg sample. Uniform adherenc e t o thi s rul e would soon familiariz e researcher s wit h its merits. Nevertheless, applyin g the rul e is optional. Because a cubi c mete r i s so large , i t ma y seem a littl e les s logica l t o expres s solution concentration s o n th e basi s o f a cubic meter, which is the S I base uni t of volume. Nevertheless , man y plant scientists hav e decided to use the cubi c meter as the base unit for solution concentrations : 1. 0 m3 = 100 0 L; thus a 1.0 mmol/L solution = 1. 0 mol m- 3. Becaus e S I rules allo w use of the liter , however , even thoug h it is not a n official par t of the system, and because concentrations base d o n the liter have long been use d by plant physiologist s (and many solutions are made up in liter quantities), i t is acceptable t o use liters i n most journals that publish papers i n th e plant sciences . (Se e discussio n belo w o n molarit y and molality ; their traditiona l units, M and m , should b e phase d ou t o f use by plant scientists.) It i s no t alway s possible o r desirabl e t o hav e only base unit s in denominators . For example , spectra l energie s must specif y a narro w wave-lengt h range , th e nanometer: mol.m-2.S-1.nm- 1 o r W.m-2.nm- 1. (Th e rang e tha t wa s actuall y measured shoul d always be stated i n the methods section) In some case s i t ma y be preferabl e t o write out informatio n fo r furthe r clarity . For example , a stric t edito r tryin g t o enforc e thi s rul e woul d insis t tha t a tem perature gradient of 1 K mm-1 be written as 1000 K m-1. I t would be better t o state: "A temperature gradien t o f 1 K over a distance of 1 mm was measured." The recommendatio n o f thi s third-leve l publication : When i t i s logical an d helpful to do so, use only SI base units in denominators. F. The Liter: Symbols and Use; Molar and Molal Solutions. Th e lite r (litre in England, France) i s not a n officia l par t of SI, probably because it is not "coherent. "

Summary of the International System of Units (SI Units) 17 To deriv e i t fro m th e cubi c meter, th e S I base unit , a multiplication factor must be used ( 1 L = 0.00 1 m 3). Th e 12t h CGP M in 196 4 declared, however, "that the word 'liter' ma y b e employe d a s a specia l nam e fo r th e cubi c decimeter " an d recom mended "tha t th e nam e lite r shoul d no t b e employe d t o giv e th e result s o f hig h accuaracy volum e measurements. " (Taylor , 1993. ) Thes e statement s effectivel y defined th e liter as exactly 1 dm3 and the milliliter (mL ) as 1 cm3. Becaus e th e liter has a convien t siz e an d th e ter m i s traditiona l an d widel y use d b y non-scientists , plant scientist s wil l continue t o us e it an d th e milliliter . Eve n th e decilite r migh t sometimes b e mos t convenient . O f course, we could use dm 3 and cm 3 as easily. In 1979 , th e CGP M considere d "that , i n orde r t o avoi d th e ris k o f confusion between the lette r 1 and the number 1 , several countries have adopted th e symbol L instead o f 1 for th e uni t liter... " I t wa s further decide d "t o adopt th e tw o symbols 1 an d L a s symbol s t o b e use d fo r th e uni t liter , considerin g furthe r tha t i n th e future onl y one o f thes e tw o symbols should be retained... " NIS T SP 811 (Taylor, 1995) strongl y recommends L as the symbo l for the liter . The vast majority of papers i n plant physiology express concentrations i n term s of molarity (symbol M = mol.L- 1) or , especiall y i n th e fiel d o f water relations , o f molality (symbo l m = mol.kg- 1). Nevertheless , bot h second-leve l authoritie s (IS O Standards Handboo k an d NIS T SP 811, Taylor , 1995 ) recommen d that th e symbols for thes e term s b e discontinued . (Althoug h no t state d i n those sources , th e term s themselves migh t still b e used. ) Th e reaso n i s that thos e uni t symbols (M and m ) are specialize d symbol s that migh t not b e understood b y someone outsid e th e fiel d (e.g., a physicist), whereas mol.L- 1 an d mol.kg- 1 are simpl e S I units understood b y anyone familia r wit h SI . Furthermore , m fo r molalit y might be mistake n a s m fo r meter. Thi s recommendatio n i s confirme d b y a n importan t third-leve l source , Quantities, Units an d Symbols i n Physical Chemistry (Mill s e t al. , 1995). Mos t plan t physiologists will no doubt continue to use the terms molarity an d probably molality, but i t is recommended tha t th e equivalent SI units be used instead of the traditiona l symbols. (Bu t see Table 1 in Chapter 10. ) G. The Dalton and the Unified Atomic Mass Unit. Man y biochemists and mos t (virtually all ) plan t physiologist s us e th e dalton (D a o r D ) a s a uni t o f atomic o r molecular mass . Th e dalto n has , however, neve r been accepte d b y the CGPM , and it i s exactly equivalent t o th e unified atomic mass unit (symbol u, Table 5) , which has bee n considere d an d accepte d b y the CGP M an d is published i n th e first-level authority. Hence , there seems t o be little excuse beyond tradition to use the dalton. Most plan t scientist s gav e u p th e einstei n i n favo r o f mol e o f photons . Th e recommendation i s to begi n t o us e the unifie d atomi c mass unit with its symbol u, probably with some explanatio n unti l it becomes mor e familiar t o plan t scientists . H. Equivalent of Gravity at the Earth's Surface. I t is common for biochemist s and other s t o expres s th e acceleratio n experience d b y a sample being centrifuged as multiples of the averag e acceleratio n cause d by gravity at th e earth's surface . Ther e has been almost n o agreement, however , on the symbol that should be used for this value. O n sees i n various publications: G , g, g, G, g, xg, an d no doubt others. Th e problem wit h these symbol s is that g is the symbo l for gram, G i s the prefi x symbo l for giga , and italic s (g ) i s reserve d fo r physica l quantitie s rather tha n units. Bold facing has no precident in the use of units. Actually , there never shoul d hav e been

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a problem becaus e the CGP M establishe d th e standard acceleration due to gravity i n 1901 and confirmed the value in 1913 . Th e primary and secondary sources show th e symbol g n. Th e logi c o f thi s symbo l i s tha t th e acceleration o f fre e fall (g ) i s a physical quantity (hence italics) that can have any value (units: m.s-2), but the standard acceleration of free fall (indicate d b y the subscript , which is no t i n italics : gn = 9.80 6 6 5 m s- 2) i s the valu e of particular interest . I t mus t be experimentall y determined an d i s thus a noncoherent unit , but multiple s of this value can be use d to describe th e acceleration caused by centrifugation (e.g., sample centrifuged for 20 min at 100 0 g n) or the acceleration experience d i n an orbiting satellite (e.g. , 10- 3 g n). This symbol , i n context , shoul d b e readil y understoo d b y everyon e withou t an y special explanation . I. Other Discarded Metric Units. Tabl e 6 include s a numbe r o f discarde d metric unit s tha t hav e no t ye t been discussed . On e occasionall y see s micron, but most of us now use th e micrometer and nanometer. Th e angstrom is seldom use d in the plan t science s bu t i s still use d in certain fields , whic h is permitted accordin g t o the footnot e i n Table 6 . Th e bar is still use d in meteorology an d sometime s i n th e field o f plant wate r relations , bu t it s replacement wit h the coheren t megapascal o r kilopascal ha s been accepte d b y most plan t physiologists. Th e hectare (ha ) will n o doubt continu e t o b e use d b y agriculturists instead o f the mor e correc t hm 2 or m 2. The Calorie (kilocalorie ) i s a part of our moder n dieting culture, but (i n the Unite d States) s o i s th e Fahrenhei t temperatur e scale ; scientist s us e degree s Celsiu s an d should also us e joules instea d o f calories. On e often see s parts per million (or billion or eve n trillion), but i t i s mor e logica l t o us e thei r equivalent s i n unit s o f mass , volume, or amoun t of substanc e (e.g. , mg.kg- 1, mmol.kg-1 , mol-L-1). Wit h suc h units, it i s not necessar y t o specif y th e basis of comparison (i.e., volume, mass, etc.). IMPORTANT REFERENCES FOR APPLICATION OF S I UNITS Many of these publication s are no w out o f date an d ar e include d here onl y for historical reference. The most recen t and most recommende d publication s that have come t o my attention ar e written in bold face. American National Metric Council. 1993. ANMC Metric Editorial Guide, Fifth Edition. American National Metric Council, 4330 East/West Highway, Suite 1117, Bethesda, MD 20814. [Anonymous]. Standar d Practic e fo r Us e o f th e Internationa l System o f Units . AST M E380-89 . American Societ y for Testing and Materials, 1916 Rac e Street , Philadelphia PA 19103. [No date.] [Anonymous]. 1992. Guidelines for measuring and reporting environmental parameters for plant experiments in growth chambers. ASA E Engineering Practice: ASAE EP411.1. American Society of Agricultural Engineers, 2950 Niles Road, St. Joseph, Michigan 49085-9659. [Thi s is Appendix C in thi s book.] [Anonymous]. 1979 . Metri c Unit s of Measure an d Styl e Guide. U . S. Metric Association, 1024 5 Andasol Avenue, Northridg e C A 91103. [Anonymous]. 1985. Radiation quantities and units. ASAE Engineering Practice: ASAE EP402. American Society of Agricultural Engineers, 2950 Niles Road, St. Joseph, Michigan 490859659. [Anonymous]. 1982 . S I Units Require d i n Societ y Manuscripts. Agronom y New s (March-Apri l 1982, p 10-13). [Anonymous]. 1988. Use of SI (metric) units. ASAE Engineering Practice: ASAE EP285.7. American Society of Agricultural Engineers, 2950 Niles Road, St. Joseph, Michigan 490859659.

Summary of the International System of Units (SI Units) 19 Boching, P.M. 1983 . Author' s Guide t o Publication in Plant Physiology Journals. Deser t Researc h Institute Pub . No . 5020. Reno , Nev . Buxton, D.R., an d D.A. Fuccillo . 1985 . Lette r to the editor. Agronom y Journal 77:512-514. [Thi s letter include s a summar y of a survey of 97 journals; 7 7 percent eithe r require d o r encourage d the us e o f S I units.] Campbell, G.S. , an d Ja n va n Schilfgaarde . 1981 . Us e o f S I unit s i n soi l physics . Journa l o f Agronomic Education . 10:73-74 . CBE Styl e Manua l Committee . 1994 . Scientifi c styl e and format : th e CB E manua l for authors , editors, and publishers . 6t h edition . Cambridg e Universit y Press, Cambridge , Ne w York. [Se e also earlie r edition s o f CBE Styl e Manual.] Downs, Robert J. 1988. Rules for using the International System of Units. HortScience 23: 811812.

Goldman, Davi d T., and R.J. Bell , editors. 1986 . Th e International System of Units (SI). Nationa l Bureau o f Standards Specia l Publicatio n 330. U . S. Department o f Commerce/National Burea u of Standards. [Se e Taylo r (1991 ) for th e mos t recent version of this publication.] Incoll, L.D., S.P . Long, and M.R. Ashmore. 1977 . S I units in publications in plant science. Curren t Advances i n Plant Sciences 9(4):331-343 . [Thi s article recommended severa l practices that ar e now in wide use b y plant scientists. I t was a kind o f historical turning point.] ISO Standards Handbook. 1993 . Quantities and Units. Internationa l Organization for Standardization, Geneve . [Thi s i s th e highl y authorative , second-leve l reference . I t i s availabl e fro m American Nationa l Standards Institute , 11 West 42n d Street, Ne w York, NY 10036. ] Mills, Ian, Tomislav Cvitas, Klaus Homann, Nikola Kallay, and Kozo Kuchitsu. 1995. Quantities, Units and Symbols in Physical Chemistry 2nd Edition. Blackwell Scientific Publications, Oxford, London, Endinburgh, Boston, Palo Alto, & Melbourne.

Monteith, J.L . 1984 . Consistenc y an d convenienc e in th e choic e of unit s fo r agricultura l science . Experimental Agriculture . 20:105-117. Petersen, M.S. Decembe r 1990 . Recommendation s for use of SI units in hydraulics. Journa l of th e Hydraulics Division, Proceedings o f the America n Society of Civi l Engineers 106:HY12. Savage, M.J . 1979 . Us e o f th e internationa l syste m o f unit s in th e plan t sciences . HortScienc e 14:493-495. Salisbury, F.B . 1991 . System Internationale: Th e us e o f SI unit s i n plan t physiology . Journa l of Plant Physiology 139(l):l-7. Taylor, Barry N., editor. 1991 . Th e International System o f Units (SI). Nationa l Institut e of Standards and Technology Specia l Publicatio n 330 . U.S . Government Printing Office , Washington , D.C. [Thi s i s th e Unite d State s editio n o f th e Englis h translation of th e sixt h edition o f "L e System Internationa l d'Unite s (SI)" , th e definitiv e publicatio n of th e Internationa l Bureau o f Weights an d Measure s an d thu s the first-leve l authority. Ther e i s also a Britis h versio n wit h slight differences , a s i n th e spellin g o f "metre, " "litre, " an d "deca. " Th e Unite d State s version i s fo r sal e b y th e Superintenden t o f Documents , U . S . Governmen t Printin g Office , Washington, DC 20402. ] Taylor, Barr y N . 1995 . Guide for th e Us e of th e International System o f Units (SI). Nationa l Institute of Standards and Technolog y Special Publication 811. [Alon g with the ISO Standards Handbook, thi s publicatio n shoul d b e considere d secon d i n authorit y onl y t o "L e System International d'Unites (SI),* a t leas t for citizens o f the Unite d States. ] Thien, S.J., an d J.D. Oster . 1981 . Th e international system of units and its particular application in soil chemistry. Journa l o f Agronomic Educucatio n 10:62-70. U.S. Metri c Association. 1993 . Guid e t o th e Us e of the Metri c System [SI Version]. U.S . Metric Assocation, Inc. , 10245 Andaso l Avenue, Northridge, CA 91325-1504 . Vorst, J.J. , L.W . Schweitzer , and V.L . Lechtenberg . 1981 . Internationa l system o f unit s (SI) : Application t o crop science. Journa l of Agronomic Educucation 10:70-72 . Weast, Rober t C. , editor. (199 5 an d ne w editions each year). CR C Handboo k of Chemistry an d Physics. CR C Press , Boc a Raton , Fla .

20 Th

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Bruce G . Bugbe e Joh Utah Stat e University Kenned Logan, Uta h Louis Sokol * Nat Boulder, Colorad o Gaithersburg

n Sage r y Space Center , Florid a Barry N . Taylor * . Inst . of Standards & Technolog y , Maryland

*Dr. Soko l i s president emeritu s o f th e U.S. Metri c Association an d a member of the National Conference o n Weights an d Measures . H e i s a certified metricatio n specialist Dr . Taylor i s the U. S. representative on th e CGPM .

2 RULES FOR BOTANICAL NOMENCLATURE John McNeil l Royal Ontari o Museum 100 Queen's Park Toronto, M5S 2C6, Canad a and Mary E. Barkwort h Biology Departmen t Utah Stat e Universit y Logan, Uta h 84322-5300, U.S.A. The following discussion provides some recommendations for documenting the plant material use d i n experimenta l an d othe r studie s an d summarize s th e rule s o f nomenclature tha t hav e been establishe d a t botanica l congresses hel d ever y five o r six years for ove r a century (for the mos t recent editio n o f the rules, see Greuter e t al., 1994) . 1. DOCUMENTATION

It i s imperativ e tha t th e plan t o r funga l materia l use d i n an y experimen t b e documented. Th e source of the seeds, plants, or cultures used should be cited i n the publication, eithe r b y indicatin g th e supplie r (e.g. , commercia l source , cultur e collection) an d includin g any cultivar or strai n identification, or else, in the cas e of material obtained fro m th e wild, by a statement of the precise geographical location . In addition , i n comparativ e studies , o r i n thos e i n whic h th e materia l woul d b e difficult o r impossibl e t o replicat e (e.g. , plant s obtained fro m mos t wil d sources) , representative materia l shoul d b e deposite d i n a recognize d herbariu m or cultur e collection, a s appropriate . Th e herbariu m specimen s should includ e plant s a t reproductive maturit y plus representative materia l o f any other stage s use d i n th e study. I f growing the plant s to th e reproductiv e stage is not feasible , the n materia l from a s matur e a plan t a s possible shoul d b e used . Th e nam e and location o f th e herbarium or culture collection wher e the specimens have been deposited shoul d be reported. Thi s can be done concisely by using the internationally accepted abbrevia tions give n in Index herbariorum (Holmgre n e t al. , 1990) , o r i n th e World Directory for cultur e collection s (Staine s e t al. , 1986) . Th e Curato r o f you r institutiona l 21

22 Th

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herbarium wil l b e abl e t o provid e advic e o n ho w t o collec t an d preserv e plan t material fo r depositio n i n th e herbarium . Usefu l advic e ca n als o b e foun d i n Fosberg & Sachet (1965) , Le e et al.(1982), Radfor d (1986), Savile (1973), and Smith (1971), or fo r fungi , i n Hawksworth (1974) . 2. TAXONOMIC GROUPS (TAXA; SINGULAR: TAXON)

All plant s ar e assigne d t o species, th e specie s t o genera (sing, genus), an d th e genera t o families. Althoug h difference s of opinion a s to circumscriptio n o f som e species, genera , an d familie s exist amon g taxonomists, there i s good agreemen t o n their limit s fo r mos t flowerin g plants. Withi n some species, infraspecifi c tax a may be recognized , usuall y a t th e rank s o f subspecies (subsp. ) o r variety (var.). Th e major rank s above th e famil y (Latin : familia) i n ascending order are: Order (ordo), Class (classis), Division (divisio) o r Phylum, and Kingdom (regnum). Classification s at these level s are more controversial, and reference to them is not usually necessary in physiological researc h publications , unles s the researc h involve s comparison o f a broad spectru m o f plants. I n further discussio n of nomenclatural practice, w e shall, therefore, conside r onl y taxa at th e ran k of family an d below. A fulle r accoun t fo r the genera l biologis t o f th e us e o f scientifi c name s o f plant s i s t o b e foun d i n Gledhill (1985) . 3. FORM OF SCIENTIFIC NAME S

A. Family names. Famil y names are plura l nouns. The y should be written ou t in full , wit h th e initia l lette r capitalized , bu t the y ar e usuall y no t italicize d o r otherwise se t ou t fro m th e res t o f th e tex t i n publication s fro m English-speakin g countries. Famil y names , apar t fro m nin e exceptions , ar e base d o n th e ste m o f a generic nam e t o whic h th e suffi x -acea e i s attached . Eigh t o f th e exception s ar e simple alternatives : Crucifera e [alternativ e base d o n genu s = Brassicaceae] , Compositae [ = Asteraceae] , Graminea e [ = Poaceae] , Guttifera e [ = Clusiaceae] , Labiatae [ = Lamiaceae] , Leguminosa e [ = Fabaceae ] (bu t se e below), Palma e [ = Arecaceae], and Umbellifera e [ = Apiaceae] . Th e alternativ e name s ma y be use d instead o f th e standar d for m bu t nee d no t be . I t is , however , desirabl e t o b e consistent withi n a paper (i.e. , do not use , fo r example , Poaceae an d Leguminosa e in the sam e paper) . The nint h alternativ e name , Papilionaceae , ca n b e use d fo r th e papilionoi d legumes i f they are regarde d a s a famil y distinc t fro m th e caesalpinioi d an d mimosoid legumes . Th e standar d form s fo r thes e thre e group s o f legumes , i f eac h i s regarded a s a family , ar e Fabacea e [ = Papilionaceae] , Caesalpiniaceae , an d Mimosaceae. Th e nam e Leguminosa e (Fabacea e i n th e broa d sense ) canno t b e use d if these three units are treate d a s distinct families . B. Names of genera. Generic names ar e compose d o f a singl e word . The y should be italicized, underlined, or se t off in some other wa y from regula r tex t (e.g. , written i n roma n i f th e tex t i s italicized) , and hav e th e initia l lette r capitalized . They ar e singula r nouns, not adjectives . The y should be written out i n ful l unles s they are use d i n combinatio n with a specifi c epithe t a s the nam e of a species (se e next item) .

Rules for Botanical Nomenclature 2

3

C. Names of species. Th e nam e o f a specie s i s a binomial . I t consist s o f th e name o f th e genu s followe d b y a singl e specific epithet. Th e epithe t (calle d th e "species name " in zoology ) ma y be hyphenated but i s never tw o separate words. I t may b e a n adjective , o r a nou n i n apposition , o r i n th e genitive . Th e entir e binomial shoul d b e italicize d o r se t of f i n som e othe r wa y from th e mai n text . Underlining i s commonly used when italics ar e no t available . As noted above , th e initia l lette r o f the generi c nam e must be capitalized. Th e initial letter of the specific epithet should not be capitalized, although capitalization is permitted if : (a ) th e epithe t is derived fro m th e nam e of a person (e.g. , Plantago Tweedyi), (b ) i t i s derived fro m a vernacular nam e (e.g., Dolichos Lablab), o r (c ) i t was once a generi c nam e (e.g. , Picea Abies). Us e o f lowercase is , however, recom mended i n all cases; i t is never incorrect . When writin g th e nam e o f a species , bot h th e generi c nam e and th e specifi c epithet mus t be given . Th e generi c nam e may be abbreviate d to th e initia l lette r followed b y a period unles s i t i s being used for the firs t tim e in a text or ther e i s a possibility o f confusion because tw o genera unde r discussion have the sam e initia l letter. I n th e latte r case , a uniqu e abbreviation consistin g of the initia l lette r an d one o r mor e others is sometimes use d fo r each o f the generi c names concerned. D. Names of infraspecific taxa. Th e name of an infraspecific taxo n is a combination o f fou r words , th e generi c name , th e specifi c epithet , th e ter m denotin g infraspecific rank , an d th e (final ) infraspecifi c epithet . (I t i s possible , althoug h uncommon, to hav e a hierarchy of infraspecific ranks ; e.g., a subspecies with several varieties.) Th e ter m denoting rank (e.g., var., subsp.) should be in the same font a s the bul k of the text , but th e other words are italicize d (or set off in some other way from th e mai n text), e.g., Stipa nelsonii subsp . nelsonii, Phyllerpa prolifera var. firma, Trifolium stellatum f. nanum. A s with specific epithets, lowercase should be used for infraspecific epithet s (bu t see "Name s of Cultivars" below). E. Citation of Authorities. T o b e accurat e an d complete , i t i s necessar y t o indicate th e name s o f th e author(s ) wh o firs t validl y publishe d a give n nam e o r combination. Thi s is usually done by citing them the firs t tim e the plan t or fungu s name i s use d i n th e text , afte r whic h the nam e ma y be use d withou t citatio n o f authors. Alternatively , i n paper s treatin g man y specie s fro m a particula r area , a statement t o th e effec t tha t th e scientifi c nomenclature follows tha t use d i n a well known Flor a o r Manua l fo r th e are a i s generall y acceptable an d ma y b e mor e informative. I n addition it i s not necessar y to cit e the author s of genera o r tax a of higher ran k unles s a pape r specificall y addresse s th e taxonom y of highe r ranks . Likewise, fo r infraspecific ranks, it is not generall y necessary to cite the authorshi p of th e specie s name , e.g. , Stipa nelsonii subsp. dorei Barkwort h & Maze. Th e onl y exception t o thi s i s when th e fina l infraspecifi c epithet i s the sam e a s tha t o f th e specific epithe t (so-calle d autonyms) . I n such instances , th e autho r of th e specie s name is given, e.g., Stipa nelsonii Scribner subsp . nelsonii. As scientific names are i n Latin (o r treate d a s Latin), th e ampersan d (& ) o r th e Lati n word 'et' shoul d b e used whe n mor e tha n on e autho r i s involved , never th e wor d 'and ' o r it s equivalents in other modern languages. Parenthese s indicate that the taxo n was originall y named i n anothe r genu s o r a t a differen t ran k but wit h th e sam e (final ) epithet .

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The nam e o f th e perso n wh o firs t validl y published th e combinatio n bein g use d appears t o the right of the parenthetica l authors . Fo r example, Agropyron cristatum (L.) Gaertne r show s that th e taxo n was first name d by Linnaeus ("L.") , who coine d the epithet cristatum for it, but tha t he adopted a different taxonomi c treatment; in this case he included i t i n another genu s (Triticum). Gaertne r wa s the firs t perso n to combin e th e epithe t cristatum with th e generi c nam e Agropyron. I n botanica l nomenclature, unlik e the practice in zoology, the person publishing the combinatio n being used , a s well as the origina l author(s) , mus t be cited . If th e name s o f author s ar e connecte d b y 'ex, ' i t mean s tha t th e author(s ) named afte r th e 'ex ' wer e responsibl e fo r valid publicatio n o f th e name , but the y attributed th e nam e t o th e author(s ) whos e name(s ) preced e th e 'ex. ' Fo r example, Carex stipata Muhlenb . e x Willd . mean s tha t Willdeno w publishe d th e combination bu t attributed it to Muhlenberg who, although he had used the epithet , had not, i n fact, previously validly published it. I f one wishes to abbreviate the cita tion, on e should retai n the name s of those actuall y publishing the combination; i.e , those afte r th e 'ex ' (i n thi s cas e 'Willd.') . Authors ' name s ar e sometime s connected b y the wor d 'in' . Thi s implie s that th e firs t perso n actuall y named th e taxon an d provide d th e description , bu t tha t i t was published in a work written by the author(s ) name d afte r th e 'in; ' e.g. , Viburnum ternatum Rehde r i n Sargen t means that Rehde r describe d an d named the species, bu t that it was published in a larger wor k writte n b y Sargent . I n suc h circumstances , th e 'in ' an d th e nam e following i t are not strictl y part of the author citation and are better omitte d unles s the plac e of publication i s being cite d (i n this case retainin g only Rehder). The name s o f author s ca n b e abbreviated , bu t t o avoi d confusion , one shoul d follow the abbreviation s use d in some standard work (e.g. Hortus Third [Baile y Hor torium, 1976] , the Authors o f Plant Names [Brummit t & Powell, 1992 ] o r a major Flora of the area) . Abbreviate d name s are followe d b y a period (e.g. , Willd . is an abbreviation fo r Willdenow in the exampl e above). In th e case s o f name s o f fungi , ":Pers. " o r ":Fries " afte r th e nam e o f th e author indicate s tha t suc h name s wer e sanctione d fo r us e b y Persoo n o r Fries , respectively, an d hav e a preferred nomenclatural status (Hawksworth, 1984) . 4. SPECIAL SITUATIONS

A. Names of Hybrids. A hybri d between tax a may be referre d t o b y placing a multiplication sig n x betwee n the names of its two parental taxa; e.g.,Agrostis L. x Polypogon Desf. , Polypodium vulgare subsp . prionodes Roth x subsp . vulgare. Som e hybrids hav e bee n give n a nam e of thei r own . Thei r hybri d status i s indicate d b y placing a multiplicatio n sig n immediatel y before th e name , e.g . xAgropogon P . Fourn. ( = Agrostis L. x Polypogon Desf.) , Mentha xsmithiana R. A Graha m ( = M . aquatica L . x M . spicata L. ) I f the mathematica l symbol is not available , a lower case 'x' should be used (not italicized) and a single space inserted between it and the name to promot e clarity ; e.g., Mentha x smithiana R.A Graham . B. Controversial or Unfamiliar Names. I f there is controversy over the nam e of a taxon , o r i f on e i s usin g th e correc t bu t stil l unfamilia r nam e fo r a taxon , a familiar alternativ e nam e (synonym ) shoul d b e give n withi n squar e bracket s (o r

Summary o f Rules for Botanical Nomenclature 2

5

otherwise indicate d parenthetically ) immediatel y after the first mention o f the name ; e.g., Achnatherum hymenoides (Roeme r & Schultes ) Barkwort h [ = Oryzopsis hymenoides (Roeme r & Schultes) Ricke r o r Stipa hymenoides Roemer & Schultes] ; or Elymus lanceolatus (Scribner & J. G . Smith) Goul d [ = Agropyron dasystachyum (Hooker) Scribne r & J. G. Smith] . C. Names of Cultivated Plants. Th e name s of cultivated plant s follo w the rule s of nomenclatur e fo r othe r plant s i n s o fa r a s thes e ar e applicabl e (e.g. , Triticum aestivum L . for th e commonl y cultivate d species o f wheat), but name s of cultivate d varieties or race s (terme d "cultivars") ar e subject to additiona l rules. Th e nam e of a cultivar follow s that of the lowes t botanical rank to which it can be assigned. Fo r example, cultivar s o f whea t woul d hav e th e cultiva r nam e give n afte r Triticum aestivum, bu t fo r hybri d te a ros e cultivars , which ar e th e resul t o f extensiv e inter specific hybridization , the cultiva r nam e would follow th e generi c nam e Rosa. The cultivar nam e is not italicized, but its initial letter is in uppercase. I t should be pu t betwee n singl e quotatio n marks , e.g. , Taxus baccata 'Variegata' ; unti l recently i t coul d als o b e precede d b y cv . (fo r cultivar) , e.g. , Taxus baccata cv . Variegata. Th e grou p o f cultivar s t o whic h it belong s ma y also b e indicated , e.g. , Rosa (Hybri d Tea ) 'Peace' . The name s o f graft-chimera s consis t o f th e name s o f th e components , i n alphabetical order , connecte d b y th e additio n (plus ) sign : "+ " (e.g. , Cytisus purpureus + Laburnum anagyroides; Syringa xchinensis + S . vulgaris). Fo r furthe r information o n th e name s o f cultivated plants , see Trehane e t al . (1995). D. Pleomorphic Fungi. Fung i with differen t phase s i n thei r life-cycl e can hav e different name s applie d t o thei r various states. Th e fungu s i n all its parts is known by the nam e of the sexually reproducing stage (teleomorph) , but , where convenient , separate name s ca n b e use d fo r th e stage s reproducing b y asexual method s (ana morphs). Anamorp h name s mak e clea r th e phase of the fungu s tha t has been use d in physiologica l studie s an d s o should b e cited wherever appropriate . E. Commo n Names . Commo n name s (o r specially formed name s in vernacular languages; e.g. , English ) ar e permitte d i n mos t journal s o f plan t physiolog y an d related sciences , but th e scientific name and its author(s) should always be stated in parentheses immediatel y following th e firs t us e of the common or vernacular name. REFERENCES Bailey Hortorium . 1976 . Hortu s third . Macmillan , New York; Collie r Macmillan , London. 1290 p . Brummitt, R.K. , an d C.E . Powell . 1992 . Author s o f Plant Names . Roya l Botani c Gardens , Kew . p 732 . Fosberg, F.R. , an d M.-H . Sachet . 1965 . Manua l for Tropical Herbaria . Internationa l Burea u fo r Taxonomy an d Nomenclature , Utrecht . p 13 2 (Regnum veg. 39). Gledhill, D . 1985 . Th e Name s of Plants. Cambridg e University Press, Cambridg e & New York. Greuter, W. , F.R . Barrie , H.M . Burdet , W.G . Chaloner , V . Demoulin , D.L. Hawksworth , P.M . Jorgensen, D.H . Nicolson , P.C. Silva , P . Trehane, an d J . McNeill. 1994 . Internationa l Code o f Botanical Nomenclature (Tokyo Code). Koelt z Scientific Books, Konigstei n Germany. (Regnum veg. 131) .

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Hawksworth, D.L . 1974 . Mycologist' s Handbook . Commonwealt h Mycological Institute, Kew. Hawksworth, D.L . 1984 . Recen t change s in the internationa l rule s affectin g th e nomenclatur e of fungi. Microbiologica l Science s 1:18-21. Holmgren, P.K. , N.H . Holmgren , an d L.C. Barnett . 1990 . Inde x Herbariorum. Par t 1 . Th e Her baria o f th e World , ed . 8 . Ne w York Botanica l Garden, Bronx , New York. 69 3 p (Regnum veg. 120) . Lee, W.L. , B.M . Bell , and J.F. Sutton , editors. 1982 . Guideline s for Acquisition and Management of Biological Specimens. Associatio n o f Systematic Collections, Lawrence, Kansas. Radford, A.E . 1986 . Fundamental s of Plant Systematics. Harpe r an d Row , Ne w York. 49 8 p. Savile, D.B.O. 1973 . Collectio n an d Car e of Botanical Specimens. (Reprin t with addendum) Publ . 1113. Agricultur e Canada , Ottawa . Smith, C.E . 1971 . Preparin g Herbarium Specimen s o f Vascular Plants. Agricultura l Information Bulletin 348, Agricultura l Research Service , Unite d State s Departmen t of Agriculture. Staines, J.F., V.F . McGowan , and V. BD. Skelman. 1986 . Worl d Directory of collections of microorganisms, ed . 3 , 678 p. Worl d Dat a Center , Brisbane . Trehane, P., C.D. Brickell , B.R. Baum , W.L.A. Hetterscheid , A.C . Leslie , J. McNeill , S.A. Spongberg, and F . Vrugtman, editors. 1995 . Th e Internationa l Code o f Nomenclature for Cultivated Plants — 1995. Quarterjack Publishing, Wimborne, U.K. p 175 (Regnum veg. 133).

Consultants Werner Greute r Noel Botanischer Garte n Ne Berlin, German y Bronx

H. Holmgren w York Botanical Garde n , New York

David L . Hawkswort h * CAB-International Mycological Institut e Kew, England

* Th e author s of this section wis h t o expres s special thanks to Professo r Hawksworth for hi s additions o f material o n funga l nomenclature , which were particularl y helpful.

3 STATISTICS Donald V . Sisson Agricultural Experimen t Statio n an d Department o f Mathematics & Statistic s Utah Stat e Universit y Logan, Uta h 84322-481 0 1.

GENERAL TERMS

experimental unit Tha t entit y t o whic h a given treatmen t i s applied. Example s include a tre e spraye d wit h a give n chemica l o r a petr i dis h containin g see d i n a particular medium . I n the latte r example, the dish is the experimenta l unit , even if there are severa l seed s i n th e dish , an d measurement s ar e mad e o n th e individua l seeds. Th e seed s ar e samples of the experimenta l unit . experimental error (or MSE) Variabilit y among experimental units that have been treated alike . Sinc e man y procedures assum e equal variances within the treatments , the bes t estimat e of experimental error involve s combinin g o r poolin g th e within treatment variability . Thi s estimat e i s usuall y called th e mean square error, o r simply the MS E (see pooled variance below) . replication Th e repeating of the application of a given treatment to more than one experimental unit . I n the petr i dis h example of the definitio n of experimental unit , the seed s ar e no t replication s bu t ar e samples. Thes e sample s ar e sometime s referred t o a s pseudoreplications. randomization Th e assignmen t o f treatment s t o experimenta l unit s a t random . This i s done t o obtai n unbiase d estimates o f the treatmen t effect s an d mean squar e error. I t remove s persona l bia s or eve n th e appearanc e o f such bias . local control (often called blocking) A restriction o n the randomizatio n impose d by th e investigato r i n orde r t o distribut e systemati c variability evenly amon g th e treatments an d t o reduc e th e unexplaine d variability, or the MSE .

2. MEASURES OF CENTRAL TENDENCY mean (X ) Th e arithmeti c averag e o f a set o f values. Thi s i s the mos t efficien t and common estimate of the "center " of a distribution but it is also affected th e mos t

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by extreme value s or outliers . I t i s usually denoted b y

or the su m of all the observations (EX ) divide d b y the number o f observations (n). median Th e middle observation afte r th e data have been ordered or ranked. I f the number o f observation s i s a n eve n number , i t i s th e averag e o f th e tw o middl e numbers afte r ranking . I t i s not affecte d b y outliers. mode Th e observation tha t occurs with the greatest frequency. I t is not very useful in smal l samples . 3. VARIABILITY range (R ) Th

e distanc e betwee n th e larges t an d smalles t observations .

standard deviation (S) Approximatel y th e averag e distanc e fro m th e mea n fo r a set o f observations. I t i s usually denoted b y

If the dat a ar e normall y distributed, or th e distributio n has the familia r bell-shape d curve, approximately two-third s o f th e observation s wil l b e withi n on e standar d deviation o f the mean and approximately 95% will be within two standard deviation s of the mean . variance (S2) Th e square of the standard deviation (really just an intermediate ste p in the calculatio n o f the standar d deviation) ,

coefficient of variation (CV) A measur e o f th e relativ e variabilit y whe n th e standard deviatio n i s expresse d a s a percentag e o f th e mea n an d th e unit s o measurement hav e been eliminated .

standard error of the mean (SX) Sinc e the mea n is itself a variable, it also ha s a standard deviation . Thi s i s denoted a s

and i s called th e standard error of the mean. Th e standar d error o f the mea n is to the mea n wha t th e standar d deviation i s to an individua l observation.

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standard error of the difference between two means (Sx1-x2 ) Th e differenc e between tw o means has a variance that is the su m of the variances of the individua l means if the two means are independent. Th e standard error of this difference is the square root o f the variance .

pooled variance I f the assumption of equal variances holds, the information within groups is pooled t o obtai n

and th e formul a for standard error o f the differenc e betwee n tw o means become s

Note tha t S P i s the sam e a s MS E (mea n square error) an d ca n be expanded t o accomodate an y number o f groups. 4.

CONFIDENCE INTERVALS

A confidence interval i s a n interva l estimat e constructe d i n suc h a wa y tha t i f a sampling experiment is repeated a large number of times and an interval constructed for eac h one , o n the averag e a specified percentage of intervals will contain th e tru e population value . I f we choose a 95 % confidence level, we usually say that we ar e 95 % confident tha t ou r interva l contain s the tru e population value. For th e populatio n mean , a confidence interval is found a s follows: where t is a value from th e table containing Student's t values (in almost all statistics books) correspondin g t o th e confidence level desired and the degrees of freedom = n- 1. For th e populatio n varianc e ( 2 ), a confidence interval is found a s follows :

where th e x 2 (chi-squared ) value s com e fro m a tabl e (foun d i n mos t statistic s books) correspondin g t o th e appropriat e confidenc e leve l an d wit h degree s o f freedom = n - 1.

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For a proportion, a confidence interva l i s found a s follows :

where

and Z is the standar d norma l variate, or t with degrees of freedom = . 5.

TEST OF HYPOTHESIS

A hypothesis test i s a procedur e t o determine whethe r a propose d conditio n (hypothesis) i s reasonabl e o r not : A. For a Population Mean. Fo r a population mean, u (mu), the conditio n i s stated a s u 0 where u O is a given value. Fo r example , we could hypothesize that th e true averag e mas s of a set o f samples was 6.5 g, or u 0 = 6. 5 g. W e us e

The hypothesi s i s rejected i f the calculate d t value exceeds th e value in the t-table , with n - 1 degrees o f freedom. B. Differenc e Between Two Population Means. Fo r the difference between two population means , th e conditio n i s stated a s where 8 (delta) i s a given value (usually 0) and

where t ha s n 1 + n 2 - 2 degree s o f freedo m i f th e populatio n variance s ca n b e assumed t o be equal. C. Populatio n Variance. Fo r a population variance, the condition i s stated as where 0

2

i s a given value, and

22

where X ha s n - 1 degrees o f freedo m an d i s compared to a tabl e o f X values , found i n mos t statistic s books.

Statistics 3

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D. Two Variances. Fo r tw o variances, th e conditio n i s stated a s and

where F is compared t o a table of F values found i n most statistics books with n1 -1 and n 2 -1 degrees o f freedom for the numerato r and denominator, respectively. E. Population Proportion. Fo r a population proportion, (pi) is stated = as , where o i s a give n value, and O

, the condition

F. Difference Between Two Proportions. Fo r th e differenc e betwee n tw o proportions, the conditio n i s stated a s 1 -2 = , where 6 i s a given value,

and

6.

REGRESSION ANALYSIS

simple linear regression A procedure for relating two continuous variables when one variabl e (dependen t variable ) i s expresse d a s a linea r functio n o f th e othe r (independent variable) . A commo n us e i s t o predic t on e variabl e base d o n th e information provide d by the other . Th e for m o f the equatio n is where Y

represent s th e predicte d value.

multiple regression A procedur e fo r expressin g on e dependen t variable a s a function o f two or mor e independen t variables. least squares techniques On e of the mathematical methods of obtaining estimates of the terms in a regression equation. Thi s method minimizes the sum of the squares of the deviatio n o f the observed Y variable (dependent ) from th e value as predicte d by the regressio n equation . slope I n th e linea r regressio n equation , Y = a + bX b i s the slop e of the line . I t represents th e predicte d average unit change in Y per unit chang e i n X . I t i s estimate d (i f th e leas t square s techniqu e is used ) b y th e formula:

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intercept I

n the linea r regressio n equation , Y = a + bX

a i s the Y intercept , o r th e predicte d valu e of Y when X = 0 . Thi s ma y have n o practical meanin g in man y problems, but i t is still a necessary part of the equation . It is estimated (i f the leas t square s techniqu e i s used) by the formula:

standard error of estimate Th e squar e roo t o f th e residua l (o r unexplained ) variance i n a regression model . Th e formul a is :

standard error of the slope A measur e o f th e variabilit y of th e slop e o f th e regression line . I t has the sam e relationship to the slop e as the standard deviation has to th e origina l variable , X. Th e formula is:

correlation coefficient A measur e o f th e mutua l linear associatio n betwee n tw o continuous variables . I t is an index as to how closely the actua l points come t o th e predicted points . Perfec t correlation i s 1 (if the slope is positive) o r -1 (if the slop e is negative) an d n o correlatio n i s represented b y 0. Th e formul a is :

coefficient of determination Thi s represents the proportion of the variability in Y (dependent variable ) tha t i s predicted b y X (independen t variable). I t is the squar e of th e correlatio n coefficient . 7.

ANALYSIS OF VARIANCE

Analysis of variance is a procedure fo r testin g the equalit y of the mean s of tw o o r more treatments by partitioning the variability into the amount caused by differences among th e treatmen t mean s an d th e amoun t cause d b y difference s amon g th e experimental unit s within the treatments . A. Experimental Designs. Experimenta l designs are th e manne r in which the treatments ar e assigne d to th e experimental units. Thre e mos t commonly encountered design s are:

Statistics 3

3

i. Completely Randomized Design (CRD). Th e treatment s ar e assigne d to experimenta l unit s with no restriction s imposed . Th e linear mode l is where Yi j represent s an individual experimental unit response , p i s the overal l mean , ii. (tau ) i s the effec t o f the ith treatment, Eij (epsilon ) i s the rando m effect associate d wit h the jth experimental unit assigne d t o the ith treatment . If w e ar e t o assum e ther e ar e k treatment s wit h n experimenta l unit s i n eac h group, and le t Y i b e th e averag e of all observations collected fro m experimenta l units assigned t o i th treatmen t an d Y b e the averag e of all the observations, th e calculations fo r th e analysis-of-varianc e table are i n Table 1. Table 1. Analysis-of-variance table for the completely randomized design. Sources of Variation

Degrees of

SV

DF

Treatments

k-1

Experimental Error

k(n-1)

Total

Kn-1

Freedom

Sums of Squares SS

Mean Square

F

MS

ii. Randomized Block Design (RBD). Th e experimental units are grouped or blocked i n such a way that th e variability from bloc k to block is greater tha n the variabilit y within blocks. Eac h treatmen t occur s once i n each block . Th e linear mode l is where Yi j represent s a n individual experimental unit response, u i s the overal l mea n ii i s the effec t o f the i * treatmen t Bj (Beta ) is th e effec t o f th e jth block. Eij i s th e rando m effect associate d with th e experimenta l unit assigned t o th e ith treatment and occurrin g in the jth block.

34 Th

e Basics

If w e assum e ther e ar e k treatment s arrange d i n b block s an d le t Y i b e th e average o f the ith group, Y . b e the average of the jth block, and Y b e the over all average, th e calculation s fo r the analysis-of-varianc e table ar e i n Table 2 . Table 2. Analysis-of-variance table for the randomized block design.

Sv

DF

Treatments

Blocks

Experimental Error

Toral

SS

MS

F

k-1

b-1

(k-1)(b-1)

kb-1

iii. Latin square design. I n the lati n square design the experimenta l units are groupe d o r blocke d i n tw o dimension s (usuall y designate d a s row s an d columns) a s oppose d t o on e dimensiona l blockin g i n th e randomize d bloc k design. Eac h treatment occur s once i n each ro w and once in each column. Th e number o f treatment s i s equa l t o th e numbe r o f row s an d th e numbe r o f columns. Th e linea r mode l is where Yijk represent s a n individual experimental unit response , u i s the overal l mean , ii i s the effec t o f the ith treatment, Bj is the effec t o f the jth row, Yk (gamma ) is the effec t o f the k th column , Eijk i s the random effect associate d wit h the experimental uni t in th e jth ro w and k t h column that was assigned to the i th treatment . If we let k equal the number of treatments (or rows or columns) an d Y i b e the average o f the ith treatment, Yj. be th e averag e of the jth row, Y k b e th e aver age of the k th column , the calculation s fo r the analysis-of-varianc e table ar e in Table 3.

Statistics 3

5

Table 3. Analysis of variance table for the latin square design.

SV Treatments

DF

SS

MS

F

k-1

rows

k -1

columns

k-1

Experimental Error

(k -1 )(k- 2)

total

k2-1

B. Mean Comparisons. Mea n comparison s ar e procedure s employe d wher e some o r all of the k treatment s mean s (or averages) are compared in an attempt t o interpret th e result s of the F-test in an analysi s of variance. i. Planned comparisons. Planne d comparison s ar e specifi c comparison s that ar e o f obvious interest, even before th e experimen t is conducted. a) Factorial experiments. Factoria l experiment s ar e experiment s i n which th e treatment s consis t o f al l possibl e combination s o f th e differen t levels o f tw o o r mor e factor s studie d simultaneously . A s a n example , consider th e respons e o f a plant to condition s when both temperatur e an d humidity ar e varied . Le t temperatur e b e factor A wit h a = 3 levels and humidity b e facto r B with b = 2 levels . Th e resultin g experimen t woul d have 3 x 2 = 6 treatments where a treatment denote s a particular combination o f temperatur e an d humidity . Assum e that ther e ar e r experimenta l units in eac h treatment . Tabl e 4 shows the schemati c layout of means.

36 Th

e Basics

Table 4. Means in a two-way factorial experiment. A = temperatur e Row Average B = humidity

Column Averag e overall average

Main Effect i s the effec t o f one facto r averaging over the level s o f all of th e other factors . Thes e ar e teste d i n the analysi s of variance usin g an F tes t (where th e mea n squar e erro r i s usually th e denominator) , a s indicated i n Table 5. Table 5. Partial analysis of variance table for a two-way factorial experiment—main effects.

SV

df

A main effect

a-1

B main effect

b-1

MS

SS

F

Interaction is the situatio n wher e differences among the levels of one factor, say factor A , change fro m leve l to leve l o f the secon d factor , say factor B. Th e tes t for a n interactio n i s also mad e in the analysi s of variance table a s indicated i n Table 6 . Table 6. Partial analysis of variance table for a two-way factorial experimentinteraction. SV

df

AB in teraction

(a-b)(b-1)

SS

MS

F

Statistics 3

7

Simple effect i s th e effec t o f on e facto r whe n al l othe r factor s ar e hel d constant. Thes e are not tested directly i n the analysis of variance table. Th e simple effec t o f B at th e a, leve l woul d be estimated b y Y12. - Y11. . I t could b e tested by using the concep t o f linear comparisons . b) Linear comparisons. Linea r comparisons are contrasts between any 2 set s (on e o r mor e mean s i n eac h set ) o f means . Th e simpl e effec t illustrated abov e is an example, and the tes t would be:

In general, i f the linea r comparison i s of the for m aY 1 ± bY 2 ± cY the variance of the linea r combination i s given by

3,

etc ,

(This assume s tha t th e Y i ' s are independent.) ii. All possible comparisons. Fisher's least significant difference test (LSD) . Al l possible differences amon g the mean s are compare d wit h the LSD value when the

where th e degree s of freedo m fo r the t ar e th e degree s o f freedom associate d with th e MSE . Thi s tes t ha s a hig h Type I error rat e (whic h also give s a low Type II error rate. ) Tukey's Test. Th e critica l value is

when q i s a valu e take n fro m a studentize d rang e tabl e (availabl e i n man y statistical textbooks) . Th e Type I error rate is low (hence the Type II error rat e is high). Newman-Keul's Test and Duncan's Test. Test s with intermediate (betwee n th e LSD and Tukey' s Test ) Type I error rates . Thes e ar e accomplishe d by ranking the means to be compared an d using different critica l values for different range s where tw o mean s adjacen t in th e ranking s hav e a range of 2 , one othe r mean between the m gives a range of 3, etc.

38 Th

e Basics iii. Orthogonal Polynomials. A compariso n amon g mean s whe n regression effects ar e emphasize d and th e objectiv e is to estimate th e for m of th e response , such as linear, quadratic , cubic, etc. Th e calculations ar e similar t o linea r combinations , wit h appropriat e weightin g coefficient s derived fo r eac h ter m i n the polynomial.

C. Variance Components. Variabilit y in a linear mode l is contributed b y two or mor e effects. I n the mode l

the rando m variability associated wit h the eij effect ca n be designate d a s s e2 . Likewise, th e variabilit y introduce d b y the treatmen t effects , ti , ca n b e desig nated a s s 2t i f treatments are considere d t o be random. Bot h s 2E an d s2T are variance component s o f this model . 8.

COVARIANCE ANALYSIS

Covariance Analysis is a combinatio n o f regressio n an d analysi s of varianc e tha t allows mea n comparison s amon g treatments in the dependen t variable to b e made after adjustin g for effects o f the independent variable. I n addition, the MSE is based on deviations fro m a regression mode l rather than deviations from th e mean, hence the MS E i s usually smaller, and we have a gain i n precision. As an example of the formulae involved, consider a randomized block design [see the mode l in equation (29) ] when the amount of nitrogen produced by alfalfa plant s is measure d unde r differen t moisture-stres s treatments . Eac h experimenta l uni t consists of 25 seeds. Sinc e germination rates ma y vary, the number germinating may be used as the independen t variable X. Th e linea r model is

where the ne w term, pXij , i s the effec t o f the germination on that experimental unit. (See table 6.)

Table 6. Simple linear analysis of covariance table for a randomized block design. Deviations from Regression Sv

df

tre atments

k-1

lbocks

experimental

error

treatment plus experimantal error

SSx

b-1

(k-1)(b-1)

b(k-1)

(treatment plus experimental error)

error Adj Means F for testing the equality of adjusted means =

SP

SSy

dF

SS

MS

40 Th

e Basics

9. NONPARAMETRIC TESTS These are test s tha t mak e a few or n o assumptions regardin g the underlyin g distribution o f th e variable . Th e powe r i s usuall y les s tha n tha t o f a correspondin g parametric test . A. Sign Test. A tes t fo r th e media n o f a population . I t classifie s eac h observation a s being either above (+) o r below (-) the hypothesized median and then tests to see if the observed proportio n abov e the median , P, differs fro m 0. 5 by using either standar d binomia l table s o r the norma l approximation to th e binomial :

B. Wilcoxon's Signed-Rank Test. A paired comparison test where the absolut e differences betwee n pair members ar e ranked, the n reassigned thei r original sign. I f there is no difference between th e two groups, the expected value of the sums of the signed ranks should be 0 . A s in many of the non-parametri c tests, a special tabl e is used t o se e i f the differenc e is significant. C. Mann-Whitney Two-Sample Test. A test for the equalit y of two populatio n means where th e dat a for both group s are pooled an d ranked. Eac h rankin g is then assigned it s accompanyin g grou p identification . Th e su m o f th e grou p wit h th e smaller sampl e size , R, i s obtained. Th e tes t i s a Z scor e o f the for m

D. Kruskal-Wallis k-Sample Test. A tes t fo r th e equalit y o f the mean s o f k different samples . I t is the counterpar t of the Analysis of Variance. Al l of the dat a from th e k group s are ranked a s one combined sample, and the group identification is then reassigne d t o each ran k value. Th e sums of the ranks, Ri, are then obtained , and a chi-squared tes t i s performed as follows :

with k - 1 degrees of freedom. E. Contingency Tables. Coun t tables where the experimental (or survey) units are classified according to tw o or more discrete variables in an attempt to determin e whether th e variable s are relate d o r independent . Ther e ar e man y techniques fo r

Statistics 4

1

analyzing these table s (categorica l dat a analysis) , but fo r tw o factor s illustrated i n Table 7 , a chi-squared tes t i s made as follows:

with d f = ( r - l)( c - 1) or th e expecte d numbe r in the i th ro w and jth column.

where and c

r = th e numbe r o f rows, = th e numbe r o f columns.

Table 7. Two-way contingency table.

Germinating

Not Germinating

O11a

O12

Group 1

Rib

R1

Group 2

021

O22

R2

Group 3

O31

O32

R3

C1

C2

nd

Cjc

a

a Oij represents the number of individuals in the ith row and jth column. b Ri represents the total of the ith row. c Cj represents the total of the jth column. d n is the total sample size.

10.

MISCELLANEOUS

A. Central Limit Theorem. On e o f th e mos t importan t practica l theorem s i n statistics. I t basicall y says tha t a s the sampl e size increases, th e distributio n o f th e sample mea n will be norma l with a mean o f u and a standard error of B. Sample Size. Th e numbe r o f experimental unit s used in each treatmen t o f an experiment. A n approximatio n t o th e number require d i s where n i s the require d sampl e size , Z i s the standar d norma l variable (1.9 6 i f one i s working with an a-level of 0.05). s i s the populatio n standar d deviation , and D i s the siz e o f the effec t on e wishe s t o detec t a s a "significant " effect . Paul N . Hinz Iowa Stat e University Ames, Iow a

Consultants Gary Richardson Colorado Stat e University Fort Collins , Colorado

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II PLANT BIOPHYSICS The science o f plant physiology relies heavil y upon a variety of biophysical measurements. I t is the goa l of this section t o summarize the symbols, units, and terms tha t are use d t o expres s th e result s o f thes e measurements . Uniformit y o f expressio n seems highl y desirable , s o thi s sectio n emphasize s recommende d S I unit s an d symbols. A t th e sam e time, i t is recognized tha t many plant scientists will continu e to us e othe r unit s an d symbols , s o acceptabl e alternative s ar e presente d i n a few cases (e.g. , millimole s pe r lite r a s a n alternativ e t o mole s pe r cubi c meter) . Definitions o f biophysical term s ar e als o given. Many physica l parameter s ca n b e considere d a s pairs , wit h on e o f th e pai r expressing a quantit y an d it s partne r expressin g a potentia l fo r transfe r o f th e quantity across a barrier. Thus , joules per kilogram are used as units to express th e quantity of hea t energ y in some substanc e unde r consideration , whil e temperatur e differences ar e use d t o expres s th e potentia l fo r transfer o f heat fro m on e poin t t o another (i.e. , from a point o f higher temperature to a point of lower temperature) . In a thermodynami c system , th e paramete r expressin g th e quantit y is sai d t o b e extensive (th e valu e i s th e su m o f th e valu e fo r subdivision s of th e system ; e.g. , volume), and the parameter expressing the transfer potential is said t o be intensive (has the sam e value fo r an y subdivision of the system ; e.g., pressure) . Mas s factor s lend themselve s wel l t o suc h a n analysis . Th e quantit y o f mas s i s expresse d a s kilograms or moles , whil e the potential s fo r transfe r ar e expresse d i n various ways: gases pressur water wate hydrogen ion s p in water

e o r partia l pressure (pascals ) r potentia l (pascals , joule s per kilogram ) H unit s

solutes i n water chemica l potentia l (o r concentratio n o r negativ e loga rithm o f concentration o r activity) Biophysical measurements i n plant physiology are ultimately dependent upo n th e concepts develope d i n physics and chemistry. T o a great extent, they depend upo n thermodynamics; hence , that i s the firs t topi c of this section .

4 BASIC THERMODYNAMIC QUANTITIES Michael J . Savag e Department o f Agronomy University o f Nata l Pietermaritzburg 320 1 Republic o f South Afric a The purpos e o f thi s chapte r i s to presen t a simple treatmen t o f some o f th e basi c thermodynamic concepts involve d in plant physiology, and especially those relatin g to water potential and its measurement. Th e concepts will be briefly applied to plant water potentia l an d to water potentia l measuremen t techniques . 1. BASIC CONCEPTS AND THE CHEMICAL POTENTIAL

Purely fro m a n energ y conservatio n standpoint , on e woul d expec t that , fo r a closed syste m (that is, one with constant mass) , the total (internal) energy change of the syste m (dE, joules) i s the heat energ y (dQ) added to th e system minus the work done (dW) by the system :

This expression i s commonly referred to as the first law of thermodynamics. Th e internal energ y E represent s th e kineti c an d potentia l energie s o f th e molecules , atoms, and subatomic particles tha t constitute the (closed) system on a macroscopi c scale; ther e i s presently no known way to determine E absolutely . Onl y changes in E, dE , ar e required , however , an d thes e change s ar e normall y determine d b y experiment. I t is also important to recognize tha t the energy of the system is totally conserved an d that the energy available for useful work is continually decreasing and being converted int o energy unavailable for useful work. Indeed , it is this unavailable energy tha t provide s insigh t int o the concep t o f system entropy . In simple terms , the chang e of entropy of a system, dS (uni t J K- 1), is the rati o of th e hea t energ y added t o th e syste m (dQ) to th e thermodynami c temperature T of the system and, in accordance with thermodynamic principles, is always increasing for an y rea l system . Thes e tw o statements are ofte n expresse d mathematicall y in differential for m as :

45

46 Plant

Biophysics

and

Entropy was first introduce d i n classical thermodynamics to provid e a quantitative basi s fo r th e commo n observatio n tha t naturall y occurring processe s hav e a particular direction . Fo r example , the flow of heat energ y occurs fro m a hotter t o a coole r region . Equation s 2 an d 3 represen t statement s o f th e second law of thermodynamics. Mechanical wor k occur s whe n work done on a system results i n motion . I f F (with uni t N ) i s the componen t o f the force acting in the directio n o f the displace ment (dl) , th e mechanica l work , dW, equals F.dl. I n this case, d W = F.dl = (F/A) •(A.dl) = P . d V , where P , whic h i s forc e (F)/are a (A) , i s th e externa l pressur e exerted o n th e syste m resultin g i n a volume change, dV (= A .dl) . Combining the first and second law s of thermodynamics (Equations 1 and 2) and the equatio n d W = P • dV describin g th e mechanica l wor k done b y the system , we have: This equatio n describe s th e interna l energ y change fo r reversibl e an d purel y mechanical thermodynami c processes. However , different system s may be subjecte d to wor k don e b y a numbe r o f force s tha t ma y or ma y not includ e pressur e (i.e. , mechanical) wor k forces. Othe r work forces could include work of magnetization, electrical work, etc. T o allow for the possibility of other work forces involved in th e closed syste m currentl y considered , w e write: where dW now represents the total of all other form s of work done by the system on the surroundings . Thi s work term can be expressed as:

where the jth work term is the product of an intensive parameter Y j an d an extensive parameter X j (Babcock , 1963 ; Bol t an d Frissel , 1960) . (Se e Chapte r 5 fo r lis t o f subscripts.) Including all forms o f work done by the system on the surroundings, the chang e in interna l energy fo r a closed syste m is expressed by:

In chemical thermodynamics , it is common for the composition of the system to be varied; i.e. , no t closed . I n such a n ope n system , in addition t o th e variable s of entropy (S), volume (V), and extensiv e parameter Xj (for given corresponding T, P, and Yj) , th e compositio n o f th e syste m i s varied . Th e amoun t o f substanc e o f chemical specie s componen t i , ni (wit h uni t mol) i s used t o describ e th e chemica l composition o f th e system . Then , choosin g S, V , Xj, and n i a s independent system

Basic Thermodynamic Quantities 4

7

variables, w e note that th e chang e i n E coul d be due to independen t change s in 5, V, Xj, an d ni, Th e chang e i n E, fo r example, du e to chang e in 5 only , with V, Xj, and n i hel d constant, ca n be expressed mathematicall y as:

The term E / S i s called a partial derivative because it expresses th e change in E with respect t o 5 only. Hence, dE = (chang e in E wit h respect t o 5 only) + (chang e in E with respec t to V only ) + (chang e i n E wit h respec t t o Xj only ) + (chang e i n E wit h respect t o ni only). Hence:

We defin e th e chemical potential ui (J mol- 1) o f th e i th solut e specie s b y th e partial chang e i n interna l energ y E wit h respect t o n i th e amoun t of substance of chemical species componen t i, with entropy S, volume V, extensive parameter Xj , an d other solut e specie s n k (k= i) kep t constant :

From Equatio n 8 and incorporating th e definition o f chemical potential of the ith solut e species , u i (Equatio n 9) , we get:

2. FREE ENERGY AND WATER POTENTIAL

The Gibbs free energy G (J) i s defined by: The Gibb s fre e energ y represents th e energy available for usefu l work . Hence , the difference in the Gibb s free energ y between two states can be used to predict the spontaneous directio n fo r a proces s an d indicate s th e usefu l wor k th e transitio n makes available. Fro m Equatio n 11 , we get:

48 Plant

Biophysics

and hence , from Equatio n 10 ,

so that :

This equation expresse s th e relationship between the Gibbs free energ y and th e chemical potentia l o f species i. Th e chemical potential of species i roughly indicates the fre e energ y associated wit h it an d available for performing work. Fo r instance , considering th e chemica l potentia l fo r water, u w,

where n k cannot b e nw, then:

where the i' indicate s tha t th e summation cannot includ e th e water component a s it has already been included . Choosin g T , P, Xj an d n k a s independent variables for ui, i t can be show n that, where € i s a dummy variable in that l . woul d not appea r if the summatio n were written out :

where

(J mol- 1),

(J mor-1),

and (J mol- 1). The quantities Si , Vi , an d Y j ar e partial molar values for entropy, volume, and intensive paramete r Yj , respectively. Definin g th e i th chemica l species t o b e water , we obtai n

Basic Thermodynamic Quantities 4 duw =

d(uw - u

w*

9

)

where we define uw* to be the chemica l potentia l o f pure free wate r at a pressure of 101.3 kP a an d a t th e sam e temperatur e a s the wate r wit h chemica l potentia l u w. Under thes e isothermal conditions, th e temperature difference indicated by dT is zero so that:

Following integratio n o f Equation 16 , we define:

and where M w (k g mol- 1) i s the partia l mola r mas s of water, the subscripts m , v , f , an d n refe r to uni t mass, volume, weight (a force), and amount of substance, respectively ; and g ( m s- 2) i s the acceleratio n du e t o gravity , V w i s the partia l molar volume of water, an d m ( J kg- 1), v ( J m- 3, N m- 2 or Pa) , f ( J N-1 or m), and n ( J mol- 1) refer t o th e specific , volumetric , weight , an d mola r wate r potentials , respectivel y (Rose, 1979 ; Savage , 1978) . Water potentia l i s the amount of useful work per unit quantity of water done by means o f externall y applie d force s i n transferring , reversibly and isothermally , a n infinitesimal amoun t of water fro m som e standard reference stat e to its position in the soil, plant , or atmosphere . Th e referenc e stat e i s that of pure free wate r at th e same temperatur e a s th e wate r i n th e syste m and a t a pressur e o f on e standar d atmosphere, namely, 101. 3 kP a (adapted fro m Taylo r an d Ashcroft, 1972 , p 153 and Bolt e t al. , 1975) . Th e S I unit of work is the joul e (J) .

50 Plant

Biophysics

Water potentia l ma y be expressed a s the amoun t o f useful wor k per uni t mass , volume, weight, o r amount o f substance (mol ) o f water. Plan t physiologist s us e th e symbol 7 fo r water potentia l an d usually define it to correspond to a volume basi s ( v ). Som e workers hav e used a mass basis ( m ) and others an amount-of-substance basis ( n ). I n any system o f units,

where, usin g S I units, p w (k g m-3) i s the densit y of liquid water, where p w = p w(T), T(°C) i s the wate r temperature , an d p w = Mw/Vw . 3. ENTHALPY

The enthalp y (H ) o f a system is defined as : As in the cas e of the Gibb s free energy , consider th e chang e of the function , i n this cas e the enthalpy , fro m a n initial equilibriu m stat e t o a fina l equilibriu m state . Therefore, dH =

d E + P.dF + V.dP = dQ + V.dP

where dE = dQ - P . d F . Hence, fo r a n isobari c process , d H i s equa l t o dQ , th e hea t energ y amoun t transferred. I n thermodynamic chemistry where isobaric processes are more important tha n isovolumi c processes , enthalpy i s of greatest use . Fro m th e definitio n of Gibbs fre e energy , the chang e in enthalpy can be defined via:

4. WATER POTENTIAL IN THE VAPOR STATE

Consider wate r vapo r (whic h ma y be jus t on e componen t o f th e ga s phase ) behaving a s an idea l gas . Then , where e (Pa ) i s the partia l water vapo r pressure , an d R (8.314 3 J mol- 1 K- 1) i s th e Universal ga s constant. W e have, from Equatio n 16,

Basic Thermodynamic Quantities 5

1

Integrating this equation ove r a vapor pressure range from P = e0 (the saturatio n vapor pressure ) t o P = e and applying Equation 24:

It ha s bee n assume d tha t isotherma l condition s prevai l durin g the chang e i n pressure fro m eo to e and that e > 0 kPa. Substitution o f Equation 1 8 into the equatio n above yields the Kelvi n equation expressing water potential = (Pa ) as a function of fractional relative humidity v e/eo:

5. COMPONENTS OF WATER POTENTIAL

Three term s emerg e fro m th e thermodynami c theory a s being component s o f water potentia l d n ( J mol- 1). I n differentia l form , fro m Equatio n 1 5 applied t o isothermal conditions , w e have:

It is desirable to partition wate r potential int o components even if there is some doubt abou t th e partitionin g (Spanner, 1973) . Ignorin g the work term, the secon d term o f Equation 27 , and writin g V w = d u w / d P an d separating

into a water part an d a non-water part, we have:

52 Plant

Biophysics

The first term, which can be positive or negative, can be written as V w • dP an d expresses th e dependence of the chemica l potentia l o f water, u w, o n pressure P. I n the olde r literature , thi s ter m i s written as dP but i n mor e moder n literatur e th e symbol d p i s used. Generally , p i s termed th e pressure potential. The secon d ter m o f the righ t hand side of Equation 28,

arises from th e contributio n of the dissolved solutes to the chemical potential o f the water (Dainty, 1976; Slatyer, 1967), commonly referred to as the osmotic component , and may be written in traditional notation a s - Vw • dpk where p k (Pa ) is referred to a s th e osmoti c pressur e arisin g fro m th e k th component . I n mor e moder n literature, th e secon d ter m i s written as V w. d p o r sometime s V W . d S wher e p (Pa ) i s termed th e osmotic potential and s (Pa ) th e solute potential. Th e old (or traditional) ter m osmotic pressure, p k, is always positive whereas the more recen t term osmoti c potentia l p (o r th e solut e potential , s) , i s always negative . The thir d term o f Equation 28 ,

expresses th e matric component arising from th e solid matter in the system, in which the chemica l potential o f water is a function o f water content (Dainty , 1976; Slatyer , 1967), may be written in traditional notation as - Vw . dt wher e - t (Pa ) is referred to a s the matric potential. Usin g th e notatio n o f the mor e moder n literature , th e third term of Equation 28 is usually written V w • d m wher e m (Pa) is also referred to as the matric potential. Th e old (or traditional) ter m t is always positive whereas the more recen t ter m m i s negative. Integrating Equation 28 and substituting for the various water potential compo nents, we have, with all terms having Pa as their unit: in traditiona l notation , or , in more modern potential terminology,

Of particular note is the controversy regarding matric potential ( — t in Equation 29 and m i n Equatio n 30 ) a s a componen t o f th e total wate r potential . Som e workers (Passioura, 1980; Salisbur y and Ross, 1991) doubt that matric potential m can be include d in Equatio n 28 as shown als o in Equations 29 and 30.

Basic Thermodynamic Quantities 5

3

6. WATER POTENTIAL OF AQUEOUS SOLUTIONS Applying Equation 27 , valid for isothermal conditions only , under conditions of constant pressur e an d i n th e absenc e of any work fields , wate r potential becomes a function o f composition an d concentratio n only . Combinin g Equations 2 6 and 2 7 and considerin g a solution containin g only one solute , sa y NaC1, we get:

where (Pa ) i s related t o vapor pressure (Equatio n 26). Equation 3 1 form s th e basi s fo r th e us e o f thermocoupl e hygrometers . Essentially these ar e instruments containing solutes, liquid, and vapor enclosed i n a sealed cavit y that can be maintained at constant temperature and pressure. Usually , the hygromete r measure s th e vapo r pressur e abov e solution , soil , o r plant-tissu e samples b y the manipulatio n o f energy flow t o an d fro m a thermocoupl e (Savage , 1982; Savag e and Cass , 1984). 7. THEORY OF THE PRESSURE-CHAMBER APPARATUS When a transpirin g lea f i s severe d (a t th e petiole) , th e xyle m sa p recedes . Pressurizing the lea f unti l the water just returns to th e cu t surface give s a measure of th e hydrostati c pressur e i n th e xyle m (Scholande r e t al , 1965) . Th e pressure chamber apparatu s i s i n fac t analogou s t o th e pressure-membran e (sometime s referred t o as pressure-plate) apparatus used mainly in soil physics (Passioura, 1980 ) to measur e matri c potential s o f soils an d othe r materials . Th e tw o methods ar e analogous in that soil matric potential is measured, but in the case of the Scholander pressure chambe r apparatus , th e matri c potential i n th e apoplas t (o r cel l wall ) i s measured. Provide d tha t the osmotic or solute potential ( S ) of the apoplastic water is close t o 0 MPa, the equation: reduces to

where p is the pressure applied to balance m , the matric potential of the apoplast, resulting i n a tota l potentia l 7 o f 0 MPa . Hence , th e matri c potential o f th e apoplast, m , i s equal to - p . I t is usually assumed that the matric potential o f the apoplast i s equal t o th e tota l wate r potential o f the symplast , s o that th e pressur e chamber the n measure s the tota l water potential o f the leaf .

ACKNOWLEDGMENTS This wor k wa s sponsore d b y th e Foundatio n fo r Researc h Development , th e Departmen t o f Agriculture, an d th e Universit y of Natal South Africa .

54 Plant

Biophysics REFERENCES

Babcock, K.L. 1963 . Theor y o f the chemica l properties of soil equilibrium. Hilgardi a 34:417-542. Bolt, G.H . an d M.J . Frissel . 1960 . Thermodynamic s o f soi l water . Netherland s Journa l o f Agricultural Scienc e 8:57-78 . Bolt, G.H. , S . Iwata, A.J. Peck , P.AC . Raats , A.A . Rode , G . Vachaud, and A.D. Voronin . 1975 . Soil physic s terminology. Bulleti n of the Internationa l Soil Science Society 48:26-36. Dainty, J . 1976 . Wate r relation s o f plan t cells . I n Encyclopedi a o f Plan t Physiology, volume 2 : Transport i n Plants II: Part A Cells , p 12-35 . Passioura, J.B . 1980 . Th e meanin g of matric potential. Journa l of Experimental Botany 31:11611169. Rose, D.A. 1979 . Soi l water: quantities , units, and symbols . Journa l of Soil Science 30:1-15. Salisbury, F.B . an d C.W . Ross . 1991 . Plan t Physiology , Fourth Edition . Wadswort h Publishing Company, Belmont , California. Savage, M.J . 1978 . Wate r potentia l term s and units. Agrochemophysic a 10:5-6 . Savage, M.J . 1979 . Us e o f th e internationa l system o f unit s in th e plan t sciences . HortScienc e 15:492-495 Savage, M.J. 1982 . Measuremen t o f water potential using thermocouple hygrometers. Unpublishe d Ph.D. thesis , Universit y of Natal, Pietermaritzburg, South Africa. 16 2 p. Savage, M.J . an d A . Cass . 1984 . Measuremen t o f wate r potentia l usin g i n situ thermocoupl e hygrometers. Advance s i n Agronomy 37: 73-126. Scholander, P.P. , H.T . Hammel , E.D. Bradstreet , an d E.A Hammingsen . 1965 . Sa p pressure i n vascular plants . Scienc e 148:339-346 . Slatyer, R.O . 1967 . Plant-Wate r Relationships . Academi c Press, Ne w York. Spanner, D.C . 1973 . Th e component s o f th e wate r potentia l i n plant s an d soils . Journa l o f Experimental Botan y 24:816-819. Taylor, S.A . an d G.L . Ashcroft . 1972 . Physica l Edaphology. W.H . Freema n an d Company , San Francisco. CONSULTANTS Keith L . Bristo w Jac CSIRO Universit Townsville, Queensland , Australi a Toronto Gaylon S . Campbell Georg Washington Stat e University Wate Pullman, Washington Pretoria Alfred Cas s Fran CSIRO Uta Glen Osmond , Sout h Australia, Australi a Logan

k Dainty y of Toronto , Ontario, Canad a e C. Green r Researc h Commissio n , South Afric a k B . Salisbury h Stat e University , Uta h

5 SOLUTIONS (IONIC RELATIONS) Jack Dainty 1 Department o f Botany University of Toronto Toronto, Ontario M5S 1A1 Canada Many event s i n plant s involv e movement s o f substance s a s gase s o r a s solutes , molecular o r ionic , dissolve d i n liquids , typicall y water . Th e followin g ar e recommended symbol s and unit s to be use d in discussion of these movements . 1. ABBREVIATIONS USED AS SUBSCRIPTS AND SUPERSCRIPTS

1 subscrip in, out subscript i, o a co, oc externa cv, vc w subscrip P subscrip V subscrip s subscrip p subscrip r o r m subscrip cw subscrip o, i superscrip

t fo r any component i n a mixture s o r superscript s denoting the directio n o f a process ; e.g., flu x fro m cytoplas m (c) t o vacuol e (v ) or fro m cytoplas m (c) t o l mediu m (o). t fo r wate r t fo r pressur e t fo r volume t for solut e t fo r osmotic potentia l t for matric potentia l t for cel l wall t use d for outside or inside of compartment (e.g., a cell).

A bar over a symbol usually means average; e.g., C= but i t ca n als o mea n partial molar as in V. .

averag e concentration ,

Current addres s is: Jac k Dainty , Mas Tourriere, F-34270 , Cazevieille , France . 55

56 Plant

Biophysics

2. THE TABLES Table 1 . Recommende d Unit s fo r Concentration s a, b ( Svmbol C ) solids in solids

mol .kg -1 or mo l mol -1 o r k g kg -1

solids in liquid s

mol-m o r k g m (S I units) mol-L-1 = M = mola r concentration (no t recommended ) mol- kg -3 = m = mola l concentration (no t recommended) , kg -L" (acceptabl e whe n no t a pur e substance ; avoi d mg-mL " , etc.)

solids in gases c

mol-m or mol-mol or kg-m-3

liquids in liquids

mol-m o r mol-mo l o r kg- m (S I units) mol-L" o r L- L o r kg- L (acceptabl e wit h S I units)

liquids in gases c

mol-m or kg-m or mol-mol-1

gases in gases c

mol- mol"1 or mol-m" 3 or m 3- m" 3 Avoid part s pe r million , part s per billion , etc.; L-L" 1 (e.g., /iL-L" 1) is acceptable.

gases in liquids c

Same as gases i n gases.

gases in solids c

mol-mol"1 or mol-kg" 1 or m 3-kg"1 (L-kg"1 is acceptable )

" Thi s table was prepared by F.B. Salisbur y in response to a suggestion o f T.W. Tibbitts . b Us e moles for pur e substances ; otherwise , us e kilograms . c Whe n volume ( m o r L) is used fo r gases, temperatur e an d pressure mus t be specified .

Table 2. Recommende d Symbol s and Unit s fo r Plant Ionic (Solution ) Relation s Unit Parameter Symbol concentration

c

i

M. m

mole fractio n activity activity coefficien t

i Xj(orXj) j) a

j

fjJ v

i

mol-m"3 mol-L4 (M = molarity ; discouraged) mol-kg-1 mol-mol"1 (dimensionless) Same units as correspondin g concentration dimensionless; use d when concentratio n is expressed in mol-m" 3, mol-L" 1, o r mol-kg ; defined b y a- = f-C- etc . dimensionless; define d by : a - = v-X-

Continued

Solutions (Ionic Relations) 5

7

Table 2. Recommended Symbols and Units for Plant Ionic Relations (continued)

Parameter Symbol

Uni

t

.• mo J-mol

l " i l

partial molar volume amount of pur e substance n chemical potential fj.: electrochemical potentia l J-mo

/-

*i

Note: Chemica l potential for nonelectrolye s or water i s given by: Ht = n' , + R T I n * j + PF , for componen t j. Electrochemica l potentia l has come t o mea n th e chemica l potentia l o f an ion and i s expressed, for io n j, by: ftt = $ + tfTlno, + P P, +z,F In thes e formula e fo r chemica l potentia l an d electrochemica l potential , R i s the ga s constan t (8.314 J mol" 1 K"1), T i s th e absolut e (kelvin ) temperature , an d F i s th e Farada y constan t (9.648 x 10 4 C-mol" 1). P i s the pressur e i n Pa, V . th e partia l molar volum e of / i n m 3 -mor 1 , Z: i s th e algebrai c valenc y (see entry below) , i p is th e electrica l potentia l i n volts (v), and a - i s the activit y i n appropriat e units . Th e chemica l and electrochemica l potential s i n th e standar d states are given by /i,* and ft, * . Fo r nonelectrolyte and ionic solute species, the pressure term, PV j is usually negligibly small. electrical potential (o electrical potential difference

r E) A# (or AEj

V V

Note: Electrica l potentia l differenc e i s often symbolize d as V or E; fo r example , th e membrane potentia l i/r' ' - i/r° = A^ is often writte n as V M or E m or V'" or E " . Strictly, however , th e symbo l E shoul d be reserve d fo r electromotiv e force ; fo r example, th e Nernst potentia l Ej fo r a n io n (see next entry) . Ej ca n b e considered a n electromotive force . Nernst potential E

jV

(volt )

Note: Th e symbol s ar e explaine d fo r the chemica l or electrochemica l potential . Th e superscripts o an d i refer t o th e outsid e an d insid e phases . algebraic valency z

. dimensionles

s

Note: Her e use d i n th e sens e o f th e numbe r of electron charges pe r ion . Th e symbols Z;+ an d 2 " are ofte n use d fo r th e charge s carried b y a catio n and a n anion , respectively . Continued

58 Plant

Biophysics

Table 2. Recommended Symbols and Units for Plant Ionic Relations (continued)

Symbol

Parameter mobility

Unit either: m^s^-V1 or: m-mol'S^-N"1

u

i

Note: Th e unit s will depen d o n whether th e drivin g force i s considered a s a voltag e gradient: m-s'VcV-m" 1), or a s a forc e pe r uni t amount o f ions: m-s'^N-mor 1). electric current 7 electrical capacitance C charge Q electrical resistance R electrical conductance G specific electrica l g conductance

A F C f S , g: S-

(amp ) (farad ) (coulomb ) l (ohm) (siemen ) m

Note: Th e symbol s g, g: can b e considered eithe r a s a slope conductance ,
- dimensionles

s

Note: Th e transpor t number , t: , is the fractio n o f an electri c current in a solution , or passing throug h a membrane, fo r instance, carried b y ion/: S t• - 1 . flux 4> influx <£ efflux 0 other (specific ) fluxe

s <£

1

, J mol-m^-s" jn, <£; , J in out, <£0, Joul oc, 0,,,,, <£„,, <£vc> etc.

Note tha t th e ter m flu x i s used i n transport studie s for amoun t crossing uni t are a pe r second. Thu s term s suc h a s "rat e o f flux " o r "flu x density " are incorrec t an d shoul d no t be used . permeability coefficien t P diffusion coefficien t D partition coefficien t K Michaelis constant

K

m-s" irr^-s" dimensionles

rate constant

A:

velocity (e.g. , of ions ) v velocity (maximu m rate o f F transport) velocity (o f reaction ) v

m-s" mav mol-m" mol-s"

1 1

s mol-mm-3 (or mol-L" 1, molarity, M, but shoul d b e avoided ) s"' m3-mol^-s"1, etc . 1

2

^"1 1

Continued

Solutions (Ionic Relations) 5

9

Table 2. Recommended Symbols and Units for Plant Ionic Relations (continued) Parameter velocity (maximu m o f enzy matically controlle d reaction ) generalized forc e generalized conductanc e coefficient quantity of substance quantity of isotope specific activit y

Symbol

Unit mol-s"1

Vmax

X

usually J-m^-mol" 1 (or N-mor 1) mol • m"2- s'V'Force"

L Q

>.

QJ s

j

mol appropriate units; e.g., th e becquerel , B q (becquerel s ar e expressed a s s" 1) appropriate units e.g., Bq-mol" 1

CONSULTANTS: se e nex t chapte i

6 WATER RELATIONS Jack Dainty Department o f Botany University of Toronto Toronto, Ontario M55 1A1 Canada In organism s i n general , bu t particularl y in plants , th e movemen t o f wate r i s of special importance . It s movemen t b y diffusio n o r bul k flo w follow s th e sam e thermodynamic principles a s the movemen t of other substances , but it s prevalenc e in livin g systems has provide d an impetu s for special study and fo r a special se t o f terms an d measurements . A t present , author s of technical paper s us e one o r th e other o f th e tw o ways o f expressing the solut e effec t o n th e chemica l potentia l of water: th e osmotic pressure o r osmotic (solute) potential. Osmotic pressure, which expresses th e effec t o f solutes as a positive number with dimensions of pressure, i s the traditiona l approach , but osmotic potential, which considers the solute effect a s a componen t o f th e wate r potential , expresse s th e effec t a s a negativ e number , usually als o wit h dimension s o f pressur e (se e Chapte r 4 on thermodynamics) . I n spite o f tradition, th e concep t o f potentials seem s most logical fro m th e standpoin t of thermodynamics, which is the basi s for the universall y accepted concep t o f water potential. I n th e followin g summar y o f recommended symbols and units , both ap proaches ar e presented , bu t th e us e o f potentials i s strongly encouraged. 1. THE TABLES The basic recommended terms , symbols, and unit s are summarized in Table 1 . Th e discussion followin g th e tabl e expand s th e basi c potentia l term s an d give s th e traditional term s a s well. Tabl e 2 then summarize s the terms , symbols, and unit s considered i n th e discussion . Tabl e 3 presents othe r term s use d i n discussion s of plant water relations.

60

Water Relations 6

1

Table 1. Recommended Terms, Symbols, & Units for Plant Water Relations Parameter

Symbol

Unit -1 J.mpl-1

chemical potential of water

Pa

water potential

Pa (Pascal)

components of water potential: pressure potential (= hydrostatic pressure), solute potential, and matric potential.

Water potentia l i s defined b y

(0.1 MPza = 11 bar; MPa is usually most approriate but kPA may also be used; J.mol-1 or J.kg-1 can also be used.)

where u **w = th e chemical potentia l

(units J.mol-1) of pure water at atmospheric pressure and at the sam e temperatur e as th e syste m unde r consideration , an d V w = th e partia l mola r volume o f water equals (1 8 000 mm3.mor-1). As discussed i n Chapter 4 on thermodynamics, division of the reference chemica l potential o f wate r (u w - u w*), which ha s unit s o f energ y ( J mol- 1), b y the partia l molar volum e o f wate r produce s unit s equivalen t t o thos e o f pressure . Thi s i s illustrated b y the followin g conversions (se e Tabl e 2 in Chapter I of this book): J.mol-1 = N . m.mol- 1 = m

2.

kg.s- 2.mol-1

Water potentia l i s often writte n as a sum of partial potentials (se e discussio n i n Chapter 4) where P = th e pressur e potentia l (actua l hydrostati c pressure , P ; positiv e o r negative), s = the osmotic potential or solute potential (often written p; sometimes, incorrectly, a s p ; always negative), an d m = th e matri c potentia l (considere d b y some not t o be a valid componen t of ; always negative). The othe r usua l way of writing the equatio n fo r water potential is : = p - p (- t ) where and P = water potentia l an d pressure as above, p = osmotic pressure ( s = -p ; uni t Pa , sometimes osmol.kg-1), and t = matric potential ( m = -r; unit Pa).

62 Plant

Biophysics

Note tha t osmotic pressure i s numericall y equivalen t t o solute potential bu t expressed a s a positiv e instea d o f a negativ e value ; ther e ar e als o positiv e an d negative versions o f matric potential ( *Pm = -T) . Use of osmotic pressure instead of osmotic potentia l i s traditional an d optional, bu t suc h a usage does no t emphasiz e that th e paramete r i s one componen t o f water potential . I t i s recommended tha t osmotic potentia l b e use d i n plant physiology. Osmotic pressure is , occasionally i n the plan t literatur e an d often in the animal literature, expresse d i n osmo l kg" 1. A valu e o f X osmol kg" 1 means RT X P a (i n pressure units) ; tha t is , th e aqueou s solutio n unde r consideratio n ha s th e sam e osmotic pressur e a s a n ideal solutio n o f molality X mol kg"1. The matric potential is the (negative ) effec t o f the soli d (and gaseous) phase s o n the water potential. It s reality is often doubted , particularl y if P and T T are correctl y interpreted. (Se e J.B. Passioura. 1980 . Th e meanin g of matri c potential. J . of Exper. Botany 31:1161-1169; F.B. Salisbury and C.W. Ross. 1991 . Plan t Physiology, Fourth Edition , Wadsworth Pub. Co., Inc; Belmont, California.) Table 2. Summary of Terms Defined and Discussed in Table 1.

Parameter water potential pressure potential (or pressure) solute or osmotic potentia l osmotic pressure

Unit

Symbol y (usuall y negative, ca n be positive)

Pa J-kg 4 Pa

¥ o r P (ca n be + o r - )

J-kg"1 Pa

*, ( V^', always negative)

J-kg"1 Pa

7T

J-kg-1

(S", = ir ;

TT i s always positive) matric potential

*m

Pa

J-kg"1

Crr;7m = -r>

Tm i s always negative; T is always positive) Table 3. Other Terms Used in Discussions of Plant Water Relations. Parameter

Symbol

volume flux

Jv

solute flux solute permeability

***, P, or o>.

Unit m-s"1

mol-m^-s"1 m-s"1

mol-m^-s'^Pa'1

Continued

Water Relations 6

3

Table 3. Other Terms Used in Discussions of Plant Water Relations (continued) Parameter Symbol

Uni

t

Note: u s i s defined b y the equation : flu x = u> sRT&Cs an d is thus given by
p

1

m-s"

-Pa'1

Note: Thi s refer s usuall y to th e cel l membran e an d i s ofte n incorrectl y calle d hydraulic conductivity. I t i s no t normalize d t o uni t thicknes s o f th e barrier . Th e ter m hydrauli c conductivity is correctly used when, for example, referring to the conductivity to water of the cell wall material; th e sam e symbo l is usually used, bu t th e unit s are m 2-s"'-Pa"1. hydraulic resistanc e R

3

( = l/L p-A, wher e A = area ) Pa-s-m"

Note: Refer s t o cells , tissues, organs , or entir e plants. diffusivity D

2

-*'1

m

Note: Denote s the "speed " a t whic h changes in water potential propagate within tissue s and incorporate s cel l and wall conductance s to water and thei r storag e capacities . diffusional permeabilit y fo r P water reflection coefficien t a

1

j m-s' dimensionles

s

Note: Fo r a membran e tha t i s leaky toward th e solut e (i.e. , no t semipermeable) , volum e flux, J v, i s given, not b y Jv = L p(bP - ATT) , bu t b y / v = LJhP - aAir). Th e reflectio n coefficient, a , expresse s th e rati o betwee n th e apparen t osmoti c pressur e an d th e thermodynamic osmotic pressure ; a , i s always less than one, an d usuall y 0 < a < 1 . volume modulu s o f elasticity e (for a cell) e

P i s defined as V(dPldV)

a 3

non-osmotic volume b

m

osmotic coefficient c/

> dimensionles

s

viscosity 7

7 N-s-m"

2

(often give n as % or m - m )

extensibility (o f cell wall) m

rn^N^-s"

1

kinematic viscosity rjj

- m-s"

1

thickness of unstirred laye r 8

m

surface tensio n T

N-m"

1

64 Plant

Biophysics CONSULTANTS FO R TH E CHAPTER S B Y JACK DAINTY

Mary A . Bisso n SUNY - Buffal o Buffalo, Ne w Yor k

John A Milbur n The Universit y of New England Armidale, Australia

Julian Collin s University o f Liverpool Liverpool, Englan d

Michael G . Pitman CSIRO Dickson, Australia

John Cra m University o f Newcastl e Newcastle, Englan d

Ronald J . Pool e McGill Universit y Montreal, Quebec , Canad a

Robert F . Davis (deceased ) Rutgers Universit y Newark, Ne w Jersey

Leonora Reinhol d Hebrew Universit y of Jerusale m Jerusalem, Israe l

Dieter Jeschk e Estenfeld, German y

Roger M . Spanswick Cornell Universit y Ithaca, New York

Betty L . Kleppe r USDA-ARS Pendleton, Orego n William J. Luca s University of California Davis, California Enid A . C . MacRobbie Botany Schoo l Cambridge, Englan d E. Marr e Universita' degl i di Milano Studii Milano, Italy

Ernst Steudl e Universitat Bayreuth Bayreuth, German y Michel Thellie r Faculte de s Sciences de Roue n Mont-Saint-Aignan, France Alan Walke r University of Sydney Sydney, Australia

7 ENERGY TRANSFER Frank B . Salisbury Plants, Soils , and Biometeorolog y Departmen t Utah Stat e University Logan, Uta h 84322-482 0 U.S.A . Michael J . Savag e Department o f Agronomy University o f Natal Pietermaritzburg 320 1 Republic o f South Afric a An excellent exampl e of plant biophysics is the applicatio n o f physical principles t o understand th e energ y exchang e betwee n a plan t an d it s environment . Here , we present a summar y table o f terms, symbols, and unit s tha t ar e appropriat e fo r thi s endeavor followe d by some equation s tha t ar e ofte n used. 1. TERMS, SYMBOLS, AND UNITS APPROPRIATE IN ENERGY-TRANSFER STUDIES The symbol s i n Table 1 are mostl y arrange d alphabetically , wit h Roman letter s first, the n Gree k letter s (bu t som e parameter s hav e alternativ e Roma n o r Gree k symbols). Table 1. Terms, Symbols, and Units. Parameter Symbol

Unit

absorption coefficient, like reflectio n coefficient, nee d no t hav e A (wavelength) specified

a

unitless

absorptance o r absorptivit y

a

unitless (J-J" 1)

heat energ y storage

B

J-kg'1, W-m' 2

boundary layer , superscript

bl

conduction, superscrip t

c

65 Continued

66 Plant

Biophysics

Table 1. Terms, Symbols, and Units (continued)

Parameter volumetric heat capacity (at constant volume) specific heat capacity of dry air (at constant pressure)

Symbol c

v

C

P

D

Unit J-m^'-C1 or J-nr 3 -K 4 J-kg^'-C 1 or J-kg^-K' 1

J

m2-s4

emissivity or emittance in infrared region, for example

eIR and EIR

unitless

water evaporation site, superscript

e

radiant energy, kinetic energy

E

diffusion coefficient of species j

J

Sleaf

nvs"1

coefficient, convective transfer coefficient, heat energy transfer coefficient heat energy convection

hc

W-nr^-C'1 or W-m^-K'1

Planck's constant

h

=6.626 x ID'34 J-s-photon 4

a quantum of radiant energy

hv

J

sensible heat energy transfer

H

W-m' 2

leaf conductance

heat energy, subscript infrared

h IR (near infrared: 800 to 3000 nm) (far infrared: 3000 to 70 000 nm)

k

unitless

thermal conductivity coefficient of region,/

K>

W-nr 2 -°C 4 orW-m- 2 -K 4

eddy diffusion coefficient of gaseous species

K

metabolic heat energy

M

foliar absorption coefficient

J

m2-s4 W-m'2, J-kg 4

photosynthetic irradiance (photosynthetically active radiation)

PAR

W-m- 2

photosynthetic photon flux (photosynthetically active radiation, photon basis)

PPF

mol-m'2-s4 (moles of photons per square meter second) (usually /imol-m -s ) (also: mol-m^-d' 1 )

partial pressure of gaseous species j

P

i

Pa (usually kPa) Continued

Energy Transfer 6

7

Table 1 . Terms , Symbols , and Unit s (continued) Parameter vapor pressure, leaf and air

Symbol e

l>ea

Unit Pa

net irradiance

Q

W-rrT2

Universal gas constant

R

8.3143 J-mol^-K' 1 8.3143 m 3 -Pa-mor 1 -K- 1 8.3143X1Q-6 m 3 -MPa-mor 1 -K- 1 (1.987 cal-mol^-K4) (0.083143 L-bar-mol^-K- 1 )

reflection coefficient

r

unitless

reflectivity (A indicates wavelength reflected)

r^ or r(A)

unitless

resistance for gaseous diffusion for species j

r

i

s-m"1

r

o

s-m

boundary-layer resistance (a for aerodynamic) diffusive resistance within a leaf relative humidity

r or r

s-m" 1

RH

percent (%)

l

(

W-m"2

solar irradiance; i.e., global irradiance

S

turbulent air, superscript

ta

transpiration, superscript

T

temperature

T

K(°C)

kinetic energy per amount of substance

U

J-mol" 1

ultraviolet

specific latent heat of vaporization; tranpiration or condensation; specific latent heat of fusion velocity, wind speed water, water vapor, subscripts distance

UV(UV-A 320 to 400 ran) (UV-B 280 to 320 nm) (UV-C <280nm) KorL

V

J-kg 4 , W-m' 2

m-s" 1

w, wv

x, or 8 (delta)

m

Continued

68 Plant

Biophysics

Table 1. Terms , Symbols, an d Unit s (continued ) Parameter

Unit

Symbol

Pa-K'1 Typical value is 66.6 Pa-K'1 (at 20°C and 100 kPa: sea level)

psychrometric constant

Y (gamma)

thickness of air boundary layer

Sbl (delta)

difference or change in the quantity that follows

A (delta)

emissivity or emittance in infrared region (as example)

6jR (epsilon)

unitless (J-J" 1 )

H. (lambda)

nm

*max (lambda)

nm

wavelength of radiation wavelength corresponding to the maximum absorption coefficient in an absorption band or to the maximum photon (or energy) emission in an emission spectrum frequency of electromagnetic radiation density of dry (unsaturated) air Stefan-Boltzmann constant

m (usually mm)

v (nu)

s'1, Hz (hertz)

P (rho)

kg-m- 3

a (sigma) or S (delta)

=5.673 x 10'8 W-m^-IC 4

2. SOME EQUATIONS USED IN HEAT-TRANSFER STUDIES A. The Energy Balance Equation for a Leaf Surface (all values can be expressed as watts per square meter: W-m"2):

Q + H + V + B + M +A = 0 where Q= ne t irradianc e (positiv e i f leaf i s radiating less energy tha n th e radian t energy absorbed fro m it s surroundings), H= sensibl e heat flux transfer (includes conduction and convection; negative if lea f loses more hea t energ y than it gains), V= laten t hea t flux ; th e transpiratio n ter m (negativ e when water i s vaporizing; positive whe n condensing o r freezing) , B= storag e flux (positive whe n leaf temperatur e is increasing), M= metabolis m an d othe r factor s (positiv e when heat i s produced), an d A= advecte d hea t flu x fro m lea f t o ai r (positiv e for advectio n fro m ai r t o leaf; advectio n i s the horizonta l flow of air—i.e. , wind). At constan t lea f temperatur e an d ignorin g metabolism an d advectio n (whic h could b e important but i s difficult t o measure) : Q + H + V = 0.

Energy Transfer 6

9

B. Radiant Energy Flux Absorbed by a Leaf Surface (Q abs; W.m-2): Qabs = eQPAR + e'Qth

where eQPAR = tota l absorbed irradianc e i n the PAR region (W.m- 2), and

e'Qth =tota l absorbed (thermal ) irradianc e outsid e PA R region (W.m-2) , e and e ' = lea f emissivitie s i n the two spectral regions .

C. Radiant Energy Flux from a Leaf (or any) Surface (Qe; W.m-2): Qe = e s T4 where Qe = Radiant energ y flux (W.m- 2), e = emissivit y (abou t 0.9 8 fo r leaves a t growin g temperatures) , a = Stefan-Boltzman n constan t (5.67 3 x 10- 8 W.m- 2-K-4), and T = absolut e temperatur e o f the lea f (K ) This Stefan-Boltzmann Law is applied i n th e nex t equation . D. Net Irradiance at a Leaf Surface (Q; W.m-2): Energy flux emitted by a leaf (Stefan-Boltzmann law) is subtracted fro m the absorbe d radiant energ y flux (Qabs) : Q = Qabs -

eIRsT4

where Q = energy flux (W.m- 2) Qabs

= absorbe d energ y flux (W.m-2), and

eIR = emissivit y or absorptivit y of the lea f fo r long-wave (thermal) radiation; typicall y about 0.9 5 fo r livin g leave s a t norma l temperature s (same a s e' above) . Often, th e abov e equatio n i s written (se e Monteit h an d Unsworth, 1990) : Q = Is - rI, + Lenv - emsT4 where 2 IS = th e sola r irradianc e inciden t a t th e lea f surface (W.m- ), r = th e lea f surfac e reflectio n coefficien t (decima l fraction) , and Lenv = th e environmental longwav e irradiance inciden t at th e leaf surfac e (W.m-2). E. Sensible Energy Flux Transfer by Convection at a Leaf Surface (H; W.m-2):

70 Plant

Biophysics

where Ta =

ai r temperature ( K or °C) ,

Tl =

lea f temperatur e (K or °C) ,

AT = T

a-

Tb

cp =

specifi c hea t capacit y o f dr y (unsaturated ) ai r ( = 100 0 J.kg- 1.K-1) at constant pressure ,

p=

densit y o f dry air (1.20 5 kg.m- 3 at 20 ° C an d 10 0 kPa),

ra=

boundary-laye r resistanc e (s.m- 1), and

ga =

boundary-laye r conductanc e (m.s- 1).

The convective transfer coefficient (h c; W.m-2.K- 1), als o calle d th e heat transfer coefficient (proportiona l t o the reciprocal of the boundary layer resistance), ma y be used t o calculat e sensible energy transfer H (W.m- 2):

F. Latent Energy Flux of Water Vapor at a Leaf Surface (V; W.m-2), the Transpiration Term:

where et = vapor pressur e i n the leaf ; i.e., withi n the substomata l cavit y (Pa) , ea = vapo r pressur e o f the air (Pa) , ra = boundary laye r resistanc e (i n air) (s.m- 1), rl = diffusiv e resistanc e withi n the lea f (s.m- 1), r=

psychrometric constan t (typicall y 66.6 Pa.K- 1), and

gl and g a = leaf an d boundary-laye r conductivitie s (m.s- 1), respectively .

Energy Transfer 7

1

REFERENCES Campbell, Gaylo n S . 1977 . A n Introductio n to Environmenta l Biophysics. Springer-Verlag , New York, Heidelberg , Berlin . 15 9 p. Gates, Davi d M . an d L a Verne E . Papian . 1971 . Atla s o f Energ y Budget s o f Plan t Leaves . Academic Press , Londo n an d Ne w York. 27 9 p. Gates, Davi d M . 1968 . Transpiration an d lea f temperature. Annua l Review of Plant Physiology 19:211-238. Larcher, Walter . 1995 . Physiologica l Plant Ecology , Thir d Edition . Springer-Verlag , Berlin , Heidelberg, New York. (Translate d b y Joy Wieser) 50 6 p. Monteith, J.L. and M.H. Unsworth. 1990 . Principle s of Environmental Physics. Edwar d Arnold : London, 29 1 p. Nobel, Park S. 1983 . Biophysica l Plant Physiology and Ecology. W.H . Freeman an d Company , San Francisco. 60 8 p. [Th e symbols and unit s used i n this chapter were modified fro m thos e i n this text book. ] Raschke, Klaus . 1960 . Hea t transfe r between th e plan t and th e environment . Annua l Review of Plant Physiolog y 11:111-126. CONSULTANTS Donald T . Krizek USDA Agricultura l Research Servic e Beltsville, Maryland John C . Sager John F. Kennedy Space Cente r Kennedy Space Center , Florid a

8 PHLOEM TRANSPORT Donald R . Geige r Department o f Biology University o f Dayto n Dayton, Ohi o 45469-232 0 U.S.A. Aart J.E . va n Bel Botanisches Institu t 1 Justus-Liebig Universita t Senckenbergstrasse 17 D-35390 Giessen, Germany In this chapte r term s ar e defined and SI units are presented whe n appropriate . Table 1. Some Terms and Units Used in the Study of Phloem Transport. Term Description of Concept Units BASIC AND DESCRIPTIVE TERMS: photoassimilates Organi c compounds produced b y photosynthetic carbon fixation . translocation Lon

g distanc e transpor t o f solute s throug h sieve tube s o r othe r structures specialized for longitudinal transport.

allocation a Flo (partitioning) ica

w o f photoassimilates int o various compartments or biochem l pathway s within sourc e an d sin k regions . I n sourc e organs , carbon i s allocate d t o variou s use s includin g export . I n a sin k organ, carbon enter s into compartments or i s used fo r synthesis , storage, or energ y metabolism.

partitioning a Distributio (allocation) pressure flow Th hypothesis em

n o f translocated photoassimilate s among sinks.

e theor y o f osmotically-drive n pressur e flow withi n th e phlo ; pressur e build s u p i n th e siev e element-companio n cel l complexes i n th e sourc e a s water move s into these sieve elemen t members i n respons e t o hig h solut e concentration s therein ; pressures within the siev e elemen t member s ar e les s i n th e sin k regions a s solute s exi t fro m th e phloem . Firs t propose d b y E . Munch i n 1930 .

Continued

Phloem Transport

73

Table 1. Some Terms and Units Used in the Study of Phloem Transport (continued) Term

Description of Concept

pressure flow A

s applie d t o phloe m transport , th e mas s flow o f wate r an d solutes along a pressur e gradient .

Units

osmotically Flo w tha t arise s fro m negativ e osmoti c potentia l withi n siev e generated flow tube s (phloe m translocation ) o r xyle m vessel s (roo t pressure , root exudation , guttation) . mass flow Flo

w o f solute alon g with solvent .

sieve-element/ Cellula companion-cell branche complex physiologica

r comple x interconnecte d b y specialize d unilaterall y d plasmodesmata ; th e comple x act s a s a n integrate d l uni t i n photoassimilate transport .

apoplast Th

e interconnecting cel l walls and water-fille d xylem elements i n a plan t throug h whic h wate r an d dissolve d solute s ca n mov e freely. I n a sense , th e "dead " par t o f a plan t but , fro m a func tional standpoint , excludin g the suberin-fille d Casparian strips.

symplast Th

e interconnected , throug h plasmodesmata , protoplast s o f a plant. Som e author s woul d exclud e th e centra l vacuoles . I n a sense, the "living " part o f a plant.

QUANTITATIVE OR translocation profile

MEASUREMENT TERMS A plo t o f solut e concentratio n versu s distance (spatia l profile) or solute concentratio n a t a particula r locatio n versu s tim e (tem poral profile) .

bidirectional Simultaneou s transpor t o f solute s i n opposit e direction s i n th e transport sam e fil e o f siev e elements . Th e proces s ha s no t bee n demon strated i n th e sens e o f th e definition . Bidirectiona l transpor t may occu r unde r som e circumstances , fo r example , in a fil e o f cells as a resul t o f cytoplasmic streaming. source A

regio n i n which net flux of solut e int o elements i s sufficient t o cause ne t expor t fro m them .

sink A

regio n i n whic h there i s ne t efflu x o f solute s an d wate r fro m sieve elements , resultin g in import int o them .

phloem loading Th

e proces s b y which product s o f carbo n assimilatio n enter int o the sieve-element/companion-cel l complex . Th e proces s ma y be: a) apoplasti c a s whe n solute s ar e transporte d acros s th e plasm a membrane of the sieve-element/companion-cel l complex , b) symplastic a s whe n solute s ar e transporte d fro m surroundin g mesophyll int o th e siev e elemen t companion cel l comple x through symplasti c connections , c ) symplasti c an d apoplasti c when bot h pathway s operate i n parallel or alternatively.

phloem Th unloading solute

e processe s tha t brin g abou t th e ne t transpor t o f wate r an d s fro m siev e element s i n sin k organs int o th e surrounding sink tissues . Passag e ou t o f th e siev e elements may b e symplastic or apoplasti c or both , depending on th e natur e of the sink . Continued

74 Plant

Biophysics

Table 1. Some Terms and Units Used in the Study of Phloem Transport (continued) Term Descriptio n o f Concept Units FLOW TERMS: phloem export Rat rate sourc

e o f phloe m translocatio n o f a specifie d solut e ou t o f a e organ. A basi s fo r comparison suc h as per leaf , per area , or pe r plan t shoul d b e specified.

mg-s'1 or mol-s"-1

phloem import Rat rate organ

e o f entr y o f a specifie d solut e throug h phloe m int o a sin k . Th e rat e shoul d b e expresse d o n a suitable basi s suc h as per specifi c sin k organ , o r pe r fres h o r dr y mas s o f th e sin k organ.

mg-s"1 or mol-s"1

phloem mass Flu flux sectiona

x o f a specifie d solut e throug h a uni t of sieve elemen t cross - mg-m -2- -s 1 l area.

translocation Linea speed (velocity ) siev

r distanc e travele d pe r uni t time b y the solutio n i n a file of e element s o r b y a concentration fron t i n a phloe m bundle .

m-s-1

osmotic-potential Th e differenc e i n osmoti c potentia l i n a fil e o f siev e element s gradient ove r a specifie d distance o f phloem path .

MPa-nT1

t flux of water enterin g siev e elements .

m'-m-V1

phloem pressur e Th e differenc e in turgor pressur e i n a file of sieve elements ove r gradient a specifie d distance.

MPa-m 4

volume flo

w Ne

" Unfortunatel y th e tw o terms ar e use d i n opposite ways by different authors. Car e must be take n t o determine which way a give n autho r chooses to appl y thes e terms .

CONSULTANTS Susan Dunfor d Coli University of Cincinnat i Universit Cincinnati, Ohi o Gle Walter Eschric h Joh GOttingen, German y Universit Donald B . Fishe r Washington Stat e University Pete Pullman, Washingto n Th R.M. Gifford CSIRO Canberra, ACT , Australi a Joh

Lim C . Ho Newcastle Institute o f Horticultur e Littlehampton, Wes t Sussex , Englan d Fran

n F. Jenner y of Adelaide n Osmond , Sout h Australia, Australia n A. Milburn y of New England Armidale, NSW , Australia r E . H . Minchin e Horticulture and Foo d Researc h Institute o f New Zealand Ltd . Lower Hutt, New Zealand n W . Patrick University of Newcastle , NSW, Australia k B . Salisbury Utah Stat e University Logan, Utah

9 ELECTROMAGNETIC RADIATION Donald T . Krizek Climate Stres s Laborator y U.S. Departmen t o f Agriculture, AR S Beltsville, Marylan d 20705-235 0 U.S.A . John C . Sager Biomedical Operation s an d Researc h Offic e (MD-RES ) John F . Kennedy Space Cente r Kennedy Space Center , Florid a 32899-000 1 U.S.A . An accurate description of the radiation environment used in controlled-environment and othe r studie s is fundamental to plan t science. Sinc e formal approva l o f the S I (Systgme International d'Unites) i n 196 0 b y th e Conference Generate de s Poids e t Mesures, ther e ha s bee n increasin g interes t amon g plan t scientist s i n tryin g t o standardize terminology used in describing electromagnetic radiation , which includes the huma n visuall y evaluate d wavelength s calle d light . Th e quantitie s use d t o describe and evaluate light (e.g., the candela, lumen, lux), however, are not applicable to plan t physiology . Th e followin g list o f terms , symbols , and unit s is base d o n recommendations give n i n th e CI E (Commission Internationale d e I'fcclairage) International Lightin g Vocabular y publishe d i n 198 7 an d i n othe r reference s attached. Table 1. Terms, Symbols, and Units Basic to Studies of Radiation". Quantity Symbol

Units

RADIATION " INCIDENT ON A FLAT SURFACE (2 DIMENSIONAL): radiant energy *

Qe

J

radiant exposure

He

J-m" 2

energy flux (irradiance) E spectral energy flux * E (spectral irradiance)

W.m-2 e^

number of photons N (number of quanta) Avogadro's number (mole) of photons

W-m~

dimensionles Q

2

-nm" 1 s mol

75 Continued

76 Plant

Biophysics

Table 1. Terms, Symbols, and Units Basic to Studies of Radiation (continued) Quantity

Symbol

Units

E

mol-m-2 mol.m-2.s-1

photon exposure H pho spectral photon flux c E

. mol-

m -s^-nm"

1

RADIATION ARRIVING AT A POINT (3 DIMENSIONAL): The quantities , symbols, an d unit s defined fo r radiatio n inciden t on a fla t surfac e (two dimensional) also apply to radiation incident on a point (three dimensional). However , th e term "fluence" has been defined as the amount of radiation incident on a spherically shaped receiver. Specifically , fluence i s the integra l of flu x at a point over al l directions about th e point. I n norma l conditions , where radiatio n come s fro m al l directions, on e mus t us e a spherical sensor t o measur e fluence. MATERIAL OR REACTION RESPONSE TO RADIATION: absorptance, absorption a factor (ratio of absorbed to incident radiation)

dimensionles

s

absorbance A

dimensionles

s

reflectance (ratio of p reflected to incident radiation)

dimensionles

s

transmittance T

dimensionles

s

" The term intensity should not be used to describe radiation falling on a surface or a point Intensity (symbol f) refers to the source', e.g., the sun or a lamp. The sam e symbo l i s use d fo r th e correspondin g energy (e ) o r photo n (p ) quantit y wit h th e subscrip t use d wher e confusion migh t occur. c Spectral data shoul d b e shown wit h th e abscissa as a wavelength scal e with lo w values t o the left Discret e responses, such a s actio n o r emissio n spectr a shoul d b e give n i n term s o f photons .

Table 2. Terms Used in Studies on Special Aspects of Photobiology (Some Relate to the Quantum Theory of Light) Quantity Symbol

Unit

s

PHOTOSYNTHESIS: frequency

/

&1, Hz

wave number

a

m'1

wavelength

A

m (visible spectrum: nm)

fluorescence

F F

initial maximum variable terminal

dimensionless

* max F

v

= F

max ' F

Continued

Electromagnetic Radiation 7

7

Table 2. Terms Used in Studies on Special Aspects of Photobiology (continued) Quantity Symbol Unit s quantum yield a (ratio of effect to number of photons)

dimensionles

m

half-peak band-width ^1/2 photosynthetically active radiation PA (Integral over pho active wavelengths, 400 to 700 (e.g. nm) (Se

s

(

nm

)

R Specif

y wavelengt h interval the first time used , 40 0 to 70 0 nm) e nex t two entries for units)

photosynthetic irradiance

PI W-m"

2

photosyntheti

PPF

mol-m-2.s-1 (usually jumol-m"2^"1) (sometimes mol- m -d" 1)

PHOTOTROPISM: Al l terminology is referenced t o th e basi c definitions and unit s of electro magnetic radiatio n PHYTOCHROME (phy): ° total phytochrome Plot

= Pf r + Pr dimensionles

s

far-red-absorbing form Pf

r dimensionles

s

red-absorbing form P

r dimensionles

s

fraction of phytochrome present in 4 Pfr form with respect to Ptot at photoequilibrium

> dimensionles

s

difference in absorbance at two h different wavelengths

A dimensionles

s

change in difference in absorbance A after irradiation with a second actinic source

A/1*2 dimensionles ^

s

U

" For a detailed description of current phytochrome nomenclature, the reader is referred to Quail et al. (1994)

REFERENCES ASAE Engineering Practice : ASA E EP285.7. 1988 . Us e o f SI (Metric) Units . America n Societ y of Agricultural Engineer s (ASAE) , 2950 Nile s Road, St. Joseph, Michiga n 49085-9659. ASAE Engineering Practice: ASAE EP402. 1990 . Radiatio n quantitie s and units. America n Society of Agricultural Engineer s (ASAE) , 2950 Niles Road, St. Joseph, Michiga n 49085-9659. ASAE Engineering Practice : ASAE EP411.2. 1992 . Guideline s for measuring and reporting environmental parameter s fo r plan t experiment s in growth chambers . America n Societ y o f Agricultural Engineers (ASAE), 2950 Niles Road St. Joseph, Michigan 49085-9659. (See appendix C.) American Societ y fo r Horticultura l Science Working Group o n Growt h Chamber s and Controlled Environments. 1980 . Guideline s for measuring and reportin g the environment for plan t studies. HortScience 15(6):719-720 .

78 Plant

Biophysics

Commission International e d e l'Eclairage . 1987 . Internationa l Lighting Vocabulary. CI E Publ. No. 17.4. Geneve , Suisse . Downs, R.J . 1988 . Rule s fo r using the International Systems of Units. HortScienc e 23(5):811-812 . Holmes, M.G. , W.H . Klei n an d J.C . Sager . 1985 . Photons , flux , an d som e ligh t o n philology . HortScience 20(1):29-31 . Krizek, D.T. 1982 . Guideline s fo r measuring and reporting environmental conditions i n controlledenvironment studies . Physiologi a Plantaru m 56:231-235. Krizek, D.T. an d J.C. McFarlane . 1983 . Controlled-environmen t guidelines . HortScienc e 18(5):662 664 and Erratu m 19(1):17 . McCree, K.J. 1972 . Th e action spectrum, absorbance , an d quantum yield of photosynthesis i n crop plants. Agricultura l Meteorolog y 9:191-216 . McFarlane, J.C . 1981 . Measuremen t an d reportin g guideline s fo r plan t growt h chambe r environments. Plan t Scienc e Bulleti n 27(2):9-ll. Mitchell, C.A . an d H.C . Dostal . 1977 . Light intensity , footcandles an d lu x are obsolet e terms . HortScience 12:437-438 . Monteith, J.L . 1984 . Consistenc y an d convenienc e i n th e choic e of units for agricultura l science. Experimental Agricultur e 20(2):105-117 . NBS Technica l Not e 910-2. 1978 . Self-Stud y Manua l on Optica l Radiatio n Measurements , Par t 1—Concepts. Unite d State s Governmen t Printin g Office, Washington , DC. North Centra l Regiona l 10 1 Committe e o n Growt h Chambe r Use . 1984 . Qualit y assuranc e procedures for accurac y in environmental monitoring-Draft proposal . Biotronic s 13:43-46 . Quail, P.H., W.R . Briggs , J. Chory, R.P . Hangarter , N.P . Harberd, R.E . Kendrick , M. Koorneef, B. Parks, R.A . Sharrock , E . Schafer , W.F . Thompso n an d G.C . Whitelam . 1994 . Spotligh t o n phytochrome nomenclature . Plan t Cel l 6:468-471. Salisbury, F.B. an d C.W. Ross . 1991 . Plan t Physiology, Fourth Edition . Wadswort h Publishin g Co., Belmont, California . Appendi x B : Radiant Energy : Som e Definitions, pp. 494-501. Shibles, R.M . 1976 . Committe e Report : Terminology pertaining to photosynthesis. Cro p Scienc e 16:437-439. Shropshire, Jr. , W . an d H . Mohr , editors . 1983 . Photomorphogenesis . Encyclopedi a o f Plan t Physiology, V. 16 A and 16B . Springer-Verlag , New York. Smith, H. an d M.G . Holmes , editors . 1984 . Technique s in Photomorphogenesis. Academi c Press , New York . Spomer, L.A . 1980 . Guideline s fo r measurin g and reportin g environmenta l factor s i n controlle d environment facilities . Communication s in Soil Science an d Plan t Analysis 11(12):1203-1208. Spomer, L.A . 1981 . Guideline s fo r measurin g an d reportin g environmenta l factor s i n growt h chambers. Agronom y Journa l 73(2):376-378 . Thimijan, R.W . an d R.D . Heins . 1983 . Photometric , radiometric , an d quantu m ligh t unit s o f measure: a review o f procedures fo r interconversion. HortScienc e 18(6):818-821 . CONSULTANTS Steven J . Brit z U.S. Departmen t o f Agriculture, ARS Beltsville, Maryland

J. Michae l Robinson U.S. Departmen t o f Agriculture, ARS Beltsville, Maryland

Gerald F . Deitzer University o f Maryland College Park , Maryland

Walter Shropshire , Jr . Omega Laborator y Timonium, Maryland

Elisabeth Gant t University of Maryland College Park , Maryland

Ambler Thompso n U.S. Department o f Commerc e Gaithersburg, Maryland

III PLANT BIOCHEMISTRY AND MOLECULAR BIOLOGY Much of plant physiology and plant science in general is plant biochemistry. Fo r th e most part , traditiona l plan t biochemistry is the same as general biochemistry , but a few specia l feature s appea r i n th e table s o f Chapter 10 . Durin g recent years , plant physiologists have become deeply involved in understanding the biochemistry of plant genetics, a field tha t i s often calle d molecular biology, the topi c of Chapter 11 .

10 PLANT BIOCHEMISTRY Clanton C . Black, Jr . Biochemistry an d Molecula r Biolog y Departmen t Life Science s Building University o f Georgi a Athens, Georgia 3060 2 U.S.A . The followin g discussio n an d table s hav e bee n extracte d fro m th e Instructions to Authors, normall y published annuall y in a January issue of Th e Journal o f Biological Chemistry (use d by permission), modified somewhat to more closely conform with SI notation an d with special referenc e t o th e plan t sciences . 1. INSTRUCTIONS ON CHEMICAL AND MATHEMATICAL USAGE A. General. I n preparing a manuscript fo r publication, make references i n th e text to simple chemical compounds by the use of formulas when these can be printed in single horizontal lines o f type. D o no t us e two-dimensional formulas in running text. Cente r chemica l equations , structura l formula , an d mathematica l formula s between successive lines of text. Prepare such structural formulas and mathematical equations in a form suitable for direct photographic reproduction and include them on a duplicate sheet at the end of the paper. Similarly , long sequences o f amin o acids o r nucleotide s usuall y reproduce bette r an d will be fre e fro m printers ' error s if they ar e printe d with a laser printer , drawn in ink, or typewritte n by the author . (Boldfaced print is best.) B. Ionic Charge should b e designated a s a numbered superscript followin g the chemical symbol ; e.g., Mg 2+, S 2-. Th e notation Mg(II ) is also acceptable . C. Optically Active Isomers. Name s o f chira l compound s whos e absolut e configuration i s known may be differentiated by the prefixe d R - and S- (see IUPA C (1970) J . Org. Chem. 35, 2849-2867) . Whe n th e compound s ca n b e correlate d sterically with glyceraldehyde, serine , or another standard accepte d for a specialized class o f compound, SMAL L CAPITAL LETTERS D-, L-, and D L may be use d for chira l compounds an d thei r racemates . Wher e the directio n o f optical rotatio n i s all that can be specified, (+)-, (-)-, and (±)- or dextro, laevo, and "optically inactive" are used, but i n suc h instances the condition s of measurement must be specified .

81

82 Plant

Biochemistry an d Molecular Biology

D. Isotopically Labeled Compounds. Th e followin g guideline s conform to th e recommendations adopted b y the IUB Committee of Editors of Biochemical Journals (CEBJ). Fo r mor e detailed instruction s consul t the IUPAC-CNO C Recommendations o n Isotopicall y Modife d Compounds (1978) Eur. J. Biochem. 86, 9-25. For mos t biochemica l usage , an isotopicall y labele d compound i s indicated by placing the symbo l for th e isotop e introduce d i n square brackets directly attached to the front of the name (word) or formula as in [ 14C]urea, [a- 14C]leucine, L-[methyl 14 C]methionine, [ 3H]CH4. I f the specific position of the labeling is known, it should be indicated a t leas t th e firs t tim e the compoun d is mentioned o r i n the Material s and Method s section ; thereafter , th e les s specifi c notatio n ca n b e used . Th e following rule s gover n mos t situations . The isotopi c prefi x precede s tha t par t o f th e nam e t o whic h i t refers , a s i n sodium [14C]formate, iodo[14C]aceticacid, 2-acetamido-7-[ 131I]iodofluorene, fructose, l,6-[l-32P]bisphosphate, B-hydroxyl[ 14C] aspartate , 17B-[ 3H]estradiol, E . coli [3H]DNA. Term s suc h a s 131 I-labeled albumi n shoul d no t b e contracte d t o [131I]albumin, sinc e nativ e albumi n doe s no t contai n iodine; however, 131 I-albumin and [ 131I]iodoalbumin ar e both acceptable . The symbo l indicatin g th e configuratio n shoul d preced e th e symbo l fo r th e isotope; e.g, D-[ 14C]glucose; L-[l- 14C]leucine; (JR)-[14C]ethanol. The sam e rule s appl y when the labele d compoun d is designated b y a standard abbreviation or symbol, other tha n the atomic symbol; e.g., [a- P]AT P or [ 32P]CMP (not CM 32P). When isotope s o f mor e tha n on e elemen t ar e introduced , thei r symbol s ar e arranged i n alphabetica l order , fo r exampl e [3- 14C,2,3-3H,15N]serine. Onl y th e symbols 2 H an d 3 H shoul d b e use d for deuterium and tritium , respectively. Whe n more than one positio n in a substance is labeled by means of the same isotope an d the positions ar e not indicated, the number of labeled atoms is added as a right-hand subscript, as in [14C2]glycoli c acid. Th e symbo l U indicates uniform an d G general labeling; e.g., [U- 14C]glucose (wher e the I4 C i s uniformaly distribute d among all six positions) an d [G- 14C]glucose (wher e the 14 C is distributed among all si x positions, but no t necessaril y uniformly); i n the latte r case it is often sufficien t t o write simply [14C]glucose. When known, the positions of isotopic labeling are indicated by Arabic numerals, Greek letters, or italicized prefixes (a s appropriate) placed within the square brackets and befor e th e symbo l of th e elemen t concerned , t o whic h they are attache d by a hyphen; example s ar e [l- 2H]ethanol, [l- 14C]alanine, L-[2- 14C]leucine (o r L-[a 14 C]leucine), [carboxy- 14C]leucine, [Me- 14C]isoleucine, [2,3- 14C]maleicanhydride, [6,7-14C]xanthopterin, [3,4- 13C,35S]methionine, L-[methyl- 14C]methionine, [1- 14C,2"C]acetaldehyde. The form s 14 CO2, 32 PO4, 32 Pi ar e acceptabl e rathe r tha n th e mor e formall y correct1 [14C]O2 or [ 14C]CO2, [32P]Pi, etc. However , the square brackets are not t o According to the IUPAC Recommendations (reference above), a distinction is made between isotopically substituted compounds (carrier-free material) where square brackets are not used (e.g. 14CO2, Na125I, CH3-C2H2-OH, (14C) carbon dioxide, sodiu m (125I ) iodide , (2-3 H2) propanol ) and isotopicall y labeled compound s where square brackets are used , either in the formula or in front of the name or formula (e.g . [14C]O2, [3H]CH3I, Na[125I], C[ 2H]3CH2O[2H] and other examples give n abov e an d i n th e IUPAC Recommendations).

Plant Biochemistry 8

3

be use d whe n th e isotopi c symbo l i s attache d t o a wor d tha t i s no t a specifi c chemical name , abbreviation , o r symbo l (e.g., 131 I-labeled, 3 H-ligands, 14 C-steroids, 14 C-amino-acids). Not e tha t th e abbreviatio n fo r Curi e i s Ci . The SI unit is the bequerel (Bq). 1 Bq = 1 disintegration pe r second o r 60 disintegrations pe r minute . 1 Ci = 3 7 x 10 9 disintegrations pe r second = 3 7 GBq. 100 0 dpm = 0.4 5 nCi = 16. 7 Bq. Th e S I unit i s preferred. E. Spectrophotometric Data. Author s reportin g spectrophotometric dat a must indicate th e relatio n betwee n th e symbols used. Althoug h a number of alternatives exist, i t i s recommended tha t author s follo w th e symbol s and terminolog y adopted by IUPAC (1970) Pure Appl. Chem. 21, 1. Beer' s law may be stated as: A = -Iog 10T = elc , wher e A i s th e absorbance ; T , th e transmittanc e ( = I /Io); e , th e molar absorbance coefficient ; c, the mola r concentration o f the absorbing substances; an d l, the lengt h o f the optica l pat h in centimeters. Unde r thes e condition s e ha s th e dimensions L-mol1-.cm- 1 (not cm 2 mol- 1). Th e ter m absorbance i s preferre d t o optical density. If Beer's law is not followe d by a particular substance in solution, this should be explicitly stated; eve n in such cases th e substance ma y be characterized by reporting the absorbanc e a t a specifie d concentration . Whe n spectrophotometri c measure ments are mad e with the us e of a radiant energy source that is not confine d strictly (as in a line spectrum) t o th e wavelengt h or frequenc y specified , the exac t value of e wil l be somewhat ambiguous ; report th e spectral characteristic s of the source . F. Molecular Weight and Mass. Ther e ar e tw o equivalen t expression s tha t should be distinquished: molecular weight (Mr, relative molecular mass) is the rati o of th e mas s of a molecule t o 1/1 2 o f the mas s of carbon 12 . Henc e i t i s dimensionless. Molecular mass (symbo l m) i n contrast i s not a ratio and can be expressed i n daltons (symbo l Da) or in atomic mass units (symbol u). Th e molecular mass is th e mass o f on e molecul e o f a substance ; i t i s thu s th e mola r mas s (M ) divide d b y Avogadro's number . Th e dalto n i s defined as 1/1 2 o f the mas s of carbon 12 . It i s correct t o sa y either "th e molecula r mas s of X i s 10,00 0 daltons " (or "1 0 kDa") o r "th e relativ e molecula r mas s (molecula r weight ) Mr = 10,000), " bu t i t i s not correc t t o expres s M r i n daltons. On e ca n use expressions such as "the 1 0 kDa peptide" an d "th e mas s o f a ribosom e i s 2. 6 x 10 7 daltons" (o r "2 6 MDa"), eve n for a n entity that i s not a definable molecule. Avoi d the use of k as a shorthand for 1000 o r fo r kDa (kilodalton) . When presenting estimate s o f relative molecula r mass from ge l electrophoresi s data, be sure to includ e the scale use d to estimate the molecular mass as one of the ordinates o n th e figure, not just the locatio n o f the various standards used. G. Equilibrium and Velocity Constants. Dissociatio n constants , association constants, an d Michaeli s constants shoul d ordinaril y be written i n terms of concentra tion; the unit s should alway s be clearly indicated at the point where the equilibrium constant i s defined an d wher e its value is given. Values o f rat e constant s shoul d b e similarl y specified , first-orde r velocit y constants bein g generall y given as s- 1. Second-orde r rat e constant s ar e ordinarily given i n M-1.s- 1 (bette r SI : L.mol-1.s- 1).

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H. Composition of Solutions and Buffers. Th e composition of all solutions an d buffers shoul d b e specifie d i n sufficien t detai l t o defin e th e concentratio n o f eac h species. Fo r ordinar y buffers, suc h as 0.1 mol.L-1 sodiu m acetate, p H 5.0 , it will be assumed that the molarity refers to the total concentration o f the various species that buffer a t th e indicated pH an d that the concentration o f the counterio n i s sufficien t to neutraliz e th e charg e of the ionize d buffe r species . Th e composition of mixtures should b e indicate d b y th e us e o f a diagona l (/ ) o r a colon . Example s are : chloroform:ether (9:1) ; 1-butanol/acetic acid/water (75:20:5). Hyphen s or dashes are not acceptabl e fo r thi s purpose . Giv e th e complet e unabbreviate d nam e an d th e source (o r a reference tha t give s the complet e composition ) for all culture media. 2. ABBREVIATIONS AND SYMBOLS All abbreviations used in a text, except those specifically indicated below (see Tables 1 to 10), should be defined in a single footnote, inserted at the beginning of the paper or immediately after the first such abbreviation. Abbreviations used only in a table or figure may be defined in the legend. Abbreviations are hindrances to readers in fields othe r than that of the author, to abstractors, an d to scientists i n foreign countries. Therefore , their use should be restricted t o a minimum . O n th e othe r hand , i t i s sometimes convenien t t o us e abbreviations o r symbol s fo r th e name s o f chemica l substances , particularl y i n equations, tables, o r figures . A limited use of abbreviations and symbols of specified meaning is therefore accepted . However , clarit y is more important than brevity. For som e o f th e mos t importan t biochemica l reagents , coenzymes , etc. , shor t abbreviations are universally employed; e.g., ATP, NAD, RNA. Th e creation of new abbreviations o f thi s kin d shoul d b e restricte d t o a n absolut e minimum . The following abbreviations are obsolete; do not use them: TCA, PCA, DTE, DOC, DMSO (us e Me2SO), SAM (use AdoMet). Do not abbreviate pyridoxal, pyridoxamine, deoxypyridoxine, thiamine, cocarboxylase, pantothenate, folate , pteroylglutamate, trichloroacetic acid , perchloric acid , the tricarboxylic acid cycle, and member s thereof. Most trivial names are sufficiently short that they do not need further shortening. Names of enzymes are usually not to be abbreviated except in terms of substrates for whic h accepted abbreviation s exist (exceptions are ATPase, DNase , and RNase) . Authors shoul d us e th e Recommende d (trivial ) Nam e give n b y th e IUPAC/TUB Committee o n Enzyme Nomenclature in "Enzyme Nomenclature Recommendations (1984)" (1984 , Academi c Press) . Excep t fo r ver y commo n enzymes, the reactio n catalyzed shoul d als o be included . Class names, such a s fatty acids, protein, etc. , or short terms (poly, furan, folate , etc.) ar e no t t o b e abbreviate d eve n whe n a n associate d ter m i s abbreviate d o r symbolized (e.g. , poly(X), not PX ; H4folate, not THF) . Symbols o r abbreviation s othe r tha n thos e liste d i n th e IUPAC-TU B Recommendations shoul d b e used onl y in those situations where an objective case may be made for necessity; none should be used when pronouns and similar short terms may replace a long word or phrase . The y should always be defined i n each paper. Suc h ad hoc abbreviations and symbols should not conflict with recommended symbols and

Plant Biochemistry 8

5

should b e introduce d onl y whe n repeate d us e i s required . If , i n exceptiona l circumstances, symbol s o r abbreviation s ar e use d i n a n abstract , the y shoul d b e defined i n th e abstrac t a s well as in th e bod y of the paper . When other abbreviations for chemical compounds ar e needed, the maximum use should b e mad e o f standar d chemica l symbol s (C , H , O , N , P , S , Na , Cl , etc.) , numerical multiples (subscripts 2 and 3, not di or D or T etc., as in Me 2SO, Me 3Si-), and o f trivia l name s an d thei r symbol s (e.g. , folate , P, Me , Pr , Bu , Ph , Ac ) (se e Tables 3 t o 10) . Thes e symbol s ma y be combine d t o represen t mor e comple x symbols, suc h a s Tos-Arg-OMe , i n whic h th e basi c structur e (arginine ) remain s recognizable. One o f the area s o f biochemistry for which special symbols ar e essentia l i s that of macromolecules. Ther e are three main series of symbols for the monomeric units, those fo r amin o acids , monosacharides , an d mononucleosides , o f which the amin o acid series is the oldest . The monomeri c unit s o f protein s ar e generall y designate d b y three-lette r symbols: a capita l followe d by two lowe r cas e letters . Th e abbreviation s shoul d ordinarily no t b e use d fo r th e fre e monomer s i n th e tex t o f papers . A standar d treatment ha s been devise d fo r th e thre e group s of macromolecules, built up fro m these units . Fo r th e amino acid residues in polypeptides, the residue with the fre e a-amino grou p (i f one i s present) i s place d a t th e lef t o f th e sequenc e a s written . Where th e sequenc e o f residues i s known, the symbol s are writte n i n order lef t t o right and joined by short lines (dashes, hyphens). Wher e the sequence is not known, the symbol s are separate d b y commas, enclosed i n parentheses. Example : Ala-Gly(Met,Pro)-Lys mean s that th e sequenc e o f methionine and proline is unknown. For th e polysaccarides, symbol s for th e sugar s ar e joine d b y short dashe s o r arrows to indicate th e link s between units . Th e position an d nature of the links are shown b y numerals and th e anomeri c symbol s a an d B . Fo r example : Maltose Glcpa1-4Gl c or Glcpa 1 4Gl c Lactose GalpBl-4Gl c o r GalpB 1 4Gl c The arro w point s awa y fro m th e hemiaceta l link . If the das h is used, it i s assumed that th e hemiaceta l lin k is to the lef t o f it. Whe n it is necessary to indicate furanose or pyranose , th e italicize d (underline d i f italics are no t available ) letter f,or p afte r the saccarid e symbo l may be used ; e.g. , Ribf for ribofuranose. Macromolecules compose d o f repeating sequence s ma y be represente d b y th e prefix 'poly ' o r the subscrip t n , bot h indicatin g 'polymer of.' Th e symbol s for th e monomeric unit s o f th e sequenc e ar e enclose d i n parentheses . Thus , poly(lys ) or (Lys)n i s polylysine ; poly(Ala-Lys ) o r (Ala-Lys) n i s a linear polyme r consistin g o f alanine and lysine in regular alternating sequence, and poly(Ala, Lys) is the irregular (random) copolymer o f equal amount s of these amino acids. Betwee n poly and th e parenthesis ther e is no intervenin g spac e o r hyphen . Th e n ma y be replace d b y a definite number , a n averag e (e.g. , 10) , o r a rang e (e.g. , 8 t o 12) , a s appropriate . 'Oligo' may replac e 'poly ' for shor t chains . See als o the legen d to Tabl e 8 regarding nucleoside an d mucleotid e symbols. Genetics—A. guid e t o nomenclatur e i n bacteria l genetic s ma y b e foun d i n Demerec, M. , Adelberg, E.A. , Clark , A.J., an d Hartman , P.E. (1966 ) Genetics 54,

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61-76. Not e that the genotypes are italicized (underline d i f italics are not available) ; phenotypes ar e not . (Se e als o Chapte r 1 1 in this volume.) Genetic designations fo r various bacteria, bacteriophages, animal viruses, algae, and other materials ar e listed i n "Genetic Maps " (Editor Stephe n J. O'Brien). Thi s publication ca n b e purchase d fro m Col d Sprin g Harbo r Laboratory , Fulfillmen t Department. P.O . Bo x 100 MM, Cold Spring Harbor, NY 11724. Th e nomenclatur e of variou s bacteri a i s liste d i n Bergey , Manual o f Determinative Bacteriology, 8t h Edition, Waverl y Press, Baltimore , M D 21202. Th e nomenclatur e o f transposabl e elements i n prokaryotes can be found i n A. Campbell et al. (1979) Gene 5, 197-206 , or Szybalsk i and Szybalsk i (1979) Gene 7, 217-270 . 3. THE TABLES

Table 1. Abbreviations of Units of Measurement and of Physical and Chemical Quantities. Thes e abbreviations ma y be used without definition. The y are no t followed by periods. Th e same form i s used in the plural. Se e Chapter 1 and Sectio n II for more information about most of these and other units. Som e are not SI units. Name Units of Concentrationa molar (moles/liter ) millimolar (millimoles/liter) micromolar (micromoles/liter ) nanomolar (nanomoles/liter ) picomolar (picomoles/liter ) Other Units becquerelc curie dalton unified atomi c mass unit (thi s is the S I equivalent o f the dalton ; its use i s preferred; se e Chapter 1 ) equivalent (shoul d be avoided ) counts per minute revolutions per minute cycles per secon d (hertz ) calorie kilocalorie swedberg (10- 13 s)

Unit/Symbol Mb, mol.L- 1 (preferred ) mM (rathe r tha n 10- 3 M) , mmol.L-1 (preferred ) uM (rathe r than 10- 6 M) , [umol.L-1 (preferred ) nM (no t muM) , nmol.L-1 (preferred) pM (no t uu M), pmol.L-1 (preferred) Bq

Ci (no t SI )

Da (no t SI ) u eq (no t SI ) cpm (no t SI , but acceptable ) rpm (no t SI , but acceptable ) Hz cal (not SI , use J) kcal (no t SI, use kJ ) S (not SI )

Continued

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Table 1. Abbreviations of Units of Measurement (continued) Name

Unit/Symbol

Physical and Chemical Quantities

absorbance A equilibrium constant K Michaelis constant K relative molecular mass M retardation facto r R average acceleration of gravity at earth's g surfaced (us e to repor t centrifugation , etc. ) specific rotatio n [a] sedimentation coefficien t s sedimentation coefficien t i n water a t 2 0 °C , extrapolated t o zero concentration diffusion coefficien t D

m r f n

t s°20,w

Thennodynamic Termse

Gibbs energy change (formerly F ) G entropy change S enthalpy change

H

a

Term s such as milligram percent (mg% ) should not be used. Mas s concentrations should be given as g/kg, mass/volume concentrations as g/L, etc. Th e lite r (preferre d symbo l L) i s accepted fo r us e with th e SI (see Chapte r 1 in thi s book).

b

Th e letter M is not an abbreviation for mole (mol); it is reserved fo r molar. Us e mM for 10- 3 M and uM for 10- 6 M . Avoid designatin g concentration s a s umo l pe r mL . Th e designatio n should , i n thi s case , properl y b e m M (i.e. , milli molar). Maintai n consistency in the use of units in situations where they are to be compared (e.g. , d o not juxtapose 10 M and 10-5 M). A s discussed i n Chapter 1 , second-level discussion s o f the SI state that molar and M should be replaced by ti e mor e readil y understandabl e (t o nonchemists ) mol-L-1 , mmol-L-1 , etc. Thi s i s supported b y physical chemist s although, a s indicate d i n thi s table , Th e Journal o f Biological Chemistry continue s t o accept th e ter m molar (M). c

1 becquerel = 1 dps or 60 dpm. 1 Ci = 3.7 x 1010 B q (37 GBq). Becquere l i s the preferred ter m in the International System o f Units .

d In the SI, the symbol g (note italics) stands for the acceleration caused by gravity at any location (e.g., on the moon well as earth). Th e subscript n (not italics ) i n the symbol g n indicates that the symbol stands for the average acceleratio n caused b y gravity at th e earth's surface (9.80665 m s-2); tha t is, gn i s a unit (Se e Chapte r 1.) e

Fo r thermodynami c term s se e th e Recommendations o f the Interunio n Commissio n o n Biothermodynamic s (J. Biol. Chem. 251, 6879-6886 . 1976 )

Table 2. Abbreviations for Semisystematic or Trivial Names. Thos e abbreviations preceded b y an asteris k ma y be use d withou t definition . Abbreviation AMP , ADP, and ATPa Adenosin * cAMP , cGMP etc. Cycli CMP-NeuAc Cytidin * Co

A (o r CoASH ) Coenzym

Name e 5' -mono, di-, and triphosphate s c AMP (adenosin e 3':5'-monophosphate), etc. e monophosph o /V-acetylneuraminic acid eA Continued

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Table 2. Abbreviations for Semisystematic or Trivial Names (continued) Name Abbreviation CoASAc Cm-cellulose CMP, CDP , an d CTP a DEAE-cellulose DNA DOPA or Dop a dTMP, dTDP, and dTTPa EDTA EGTA FAD and FADH 2 FMN GDP-Fuc GDP-Man GMP, GDP , an d GTPa GSH an d GSS G Hb, HbCO, HbO 2, metHb Hepes or HEPE S IMP, IDP, an d ITPa Me2SO NAD, NAD+ , an d NAD H NADP, NADP + , and NADP H Pi PPj

RNA SDS TEAE-cellulose TMP, TDP , an d TIPa

Tris UDP-Gal UDP-GalNAc UDP-Glc UDP-GlcNAc UDP-GlcUA UDP-Xyl UMP, UDP , an d UTPa a

Acetyl coenzym e A

O-(Carboxymethyl)cellulose

Cytidine 5 ' -mono- , di-, and triphosphates O-(Diethylaminoethyl)-cellulose Deoxyribonucleic aci d or deoxyribonucleat e 3,4-Dihydroxphenylalanine Thymidine 5'-mono- , di, and triphosphate s Ethylenediaminetetraacetate [Ethylenebis(oxyethylenenitrilo)]tetraacetic aci d Flavin-adenine dinucleoiid e an d it s full y reduce d for m Riboflavin 5'-phosphat e Guanosine diphosphofucos e Guanosine diphosphomannos e Guanosine 5'-mono- , di, and triphosphate s Glutathione an d it s disulfide for m Hemoglobin, carbo n monoxid e hemoglobin, oxyhemo globin, methemoglobi n 4-(2-Hydroxyethyl)-l-piperazineethanesulfonic acid Inosine 5'-mono- , di- , and triphosphate s Dimethyl sulfoxid e Nicotinamide-adenine dinucleotide and it s oxidized and reduced form s Nicotinamide-adenine dinucleotide phosphate an d it s oxidized an d reduce d form s Inorganic phosphat e Inorganic pyrophosphat e Ribonucleic aci d or ribonucleat e Sodium dodecy l sulfat e O-(Triethylaminoethyl)cellulose Ribosylthymine 5 ' -mono, di- , and triphosphate s Tris(hydroxymethyl)aminomethane Uridine diphosphogalactos e Uridine diphosph o N-acetylgalactosamin e Uridine diphosphoglucos e Uridine diphosph o N-acetylglucosamine Uridine diphosphoglucuroni c acid Uridine diphosphoxylos e Uridine 5'-mono , di- , and triphosphate s

Th e d prefix ma y be use d t o represent the corresponding deoxyribonucleoside phosphates ; e.g., dADP . Th e various isomers o f adenosin e monophosphat e ma y be written 2'-AMP- , 3'-AMP , o r 5'-AM P (i n cas e o f possibl e ambiguity) . A simila r procedur e ma y be applied t o other nucleosid e o r deoxyribonucleosid e monophosphates .

Plant Biochemistry 8

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Table 3. Miscellaneous Symbols. Mos t of these abbreviations ma y be used withou t definition. Som e (e.g. , Q, K ) should b e define d th e firs t tim e the y are used . Symbol

Name

Symbol

Name

Ferredoxin Menaquinone Plastoquinone Phosphoric acid residu e Phylloquinone Pteroic acid (pteroyl- ) Pteroylglutamic acida PyridoxylTocopherol

Fd MK Q P- o r - P K Pte PteGlu PxyT

TQ Tocopherolquinone Ubiquinone Q CD Circular dichroism ORD Optical rotar y disperson NMR Nuclear magneti c resonance ESR Electron spi n resonanc e EPR Electron paramagneti c resonance IR spectra Infrared spectr a UV Ultraviolet

a

Folate and folyl- are not abbreviated.

Table 4. Symbols for Amino Acids. Th e symbol s precede d b y an asteris k ma y b e used withou t definition . Th e us e o f the one-lette r abbreviation s (i n parentheses ) should be restricted to comparisons of long sequences in tables, lists, or figures , and for suc h special use a s tagging three-dimensiona l model s o f proteins. The y shoul d not b e use d i n paper s wher e th e single-lette r syste m fo r nucleosid e sequence s i s employed, a s i n repeatin g codons . Di(-amin o acids ) ar e liste d i n appendi x B of Nomenclature of -Amin o Acids, CBN (1975) Biochemistry 14, 449-462 . Name Alanine 3-Aminopropionic aci d Arginine Asparagine Aspartic acid Aspartic acid or asparagin e 4-Carboxyglutamic acid Cysteine Glutamic acid Glutamine Glutamic acid or glutamine Glycine Half-cystine Histidine Homocysteine Homoserine

Symbol Ala (A ) BAla Arg (R ) Asn (N ) Asp (D ) Asx (B ) Gla Cys (C ) Glu (E ) Gln (Q ) Glx (Z ) Gly (G ) Cys His (H ) Hey Hse

Name

Symbol

Homoserine lacton e Hse> Hydroxylysine Hyl Hydroxyproline Hyp Isoleucine He (I)Leucine Leu (L ) Lysine Lys (K ) Methionine Met (M ) Ornithine Orn Phenylalanine Phe (F ) Proline Pro (P ) 5-Pyrrolidone-2-carboxylic acid
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Table 5. Symbols for Carbohydrates and Organic Acids. Thos e symbol s preceded by a n asteris k ma y be use d withou t definition . Pyranos e and furanos e forms ar e designated where necessar y by the suffixe s p an d /. Carbohydrate Simple sugars Arabinose Fructose Fucose Galactose Glucose Mannose Rhamnose Ribose Xylose Derivatives of various sugars N-Acetylglucosamine Glucosamine 2-Deoxyglucosea Glucuronic acid Reductive Pentos e Phosphate Cycle 6 Phosphogluconi c Acid Fructose-l,6-bisphosphate Fructose-6-phosphate Xylulose-5 -phosphate Sedoheptulose-7-phosphate Sedoheptulose 1,7-bisphosphat e 3-Phosphoglycerate Glyceraldehyde-3-phosphate Dihydroxyacetone phosphate Erythrose-4-phosphate Fructose-2,6-bisphosphate Glucose-1,6-bisphosphate Sialic Acid Organic Acids of the Tricarboxylic Acid cycle Oxalacetic Acid Citric Acid a-Ketoglutaric Acid , 2-oxoglutorat e Succinic Acid Malic Acid Fumeric Acid Isocitric Acid Pyruvic Acid Phosphoenolpyruvic Acid Cis-Aconitate

Symbol

Ara Fru Fuc Gal Glc Man Rha

Rib Xyl

GlcNAc GlcN dGlc GlcA RPPC 6PGL Fru-l,6-BP or FBP or F1,6-P 2 Fpu-6-P o r F6 P Xylu-5-P or X5P Sedoh-7-P o r S7P Sedoh-l,7-BP o r S1,7-P 2 3-PGA GAP DHAP E-4 P or Ery-4-P Fru2,6-Bp o r F2,6-P 2 Glul,6-Bp o r G1,6-P 2 Sia

OAA CIT a-KG, 2-O G

SUC

MAL FUM ISOCIT PYR PEP cACN

aThe prefix 'd' indicates a 2-deoxysugar. Isomers may be designated similarly with a positional numerial; e.g., 3-aThe prefix ' deoxyglucose; 3-dGlc . Note: I n case s where the distinction between N-acetyl and O-acety l i s important, NeuNA c or NeuOA c ar e acceptabl e with definition . Likewise , NeuNGc and NeuOG c ar e acceptabl e fo r th e glycolyl analogs.

Plant Biochemistry 9

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Table 6. Symbols for Pyrimidine and Purine Bases. Thes e symbol s shoul d b e defined excep t thos e marked wit h an asterisk . Base Adenine * 'a base' Bas Cytosine * Guanine * Hypoxanthine Hy 6-Mercaptopurine (thiohypoxanthine ) Sh Orotate Or 'a purine' Pu 'a pyrimidine' Thymine * Uracil * Xanthine *

Symbol Ad Cy Gu

Th Ur Xa

e e t a p y o r Pyr y a n

Table 7. Symbols for Nucleosides and Nucleotides. Symbol s preceded b y an asteris k may be used withou t definition. Tw o systems are recognized, one using three-lette r symbols for the common nucleosides an d a capital italic P for the phosphoric residue, the othe r usin g single capita l letter s fo r th e commo n nucleosides and a lowe r case p fo r th e phosphori c residue . Th e three-lette r symbol s should b e use d whenever chemical changes involvin g nucleosides o r nucleotides are discussed. Th e one-lette r symbols ar e intende d fo r th e nucleosid e residue s i n sequences or partia l sequence s only; i n thes e the y shoul d alway s be connecte d b y hyphens (for internal phospho diester 3 ' -5' linkages) , an d the terminal phosphoric residu e should be indicated by the letter p. Codon s ma y be indicated i n the tex t without hyphens or th e termina l p's. Th e 2'-deoxyribonucleoside s ar e indicate d b y the prefi x 'd' . Fo r incompletel y specified base s i n nucleotid e sequences , see (1986 ) J. Biol. Chem. 261 , 13-17 . Nucleoside Adenosine Bromouridine Cytidine Dihydrouridine Guanosine Inosine 6-Mercaptopurine ribonucleosid e (6-thioinosine ) 'a nucleoside ' Orotidine Pseudouridine 'a purin e nucleoside ' 'a pyrimidin e nucleoside '

Symbol Three-letter One-letter * Ad o BrUrd * Cy d * Gu o * In o Sno Nuc Ord *r d Puo Pyd

*A B *C D or h U *G *I M or M P N O or Qa * R Y

Continued

92 Plant

Biochemistry and Molecular Biology

Table 7. Symbols for Nucleosides and Nucleotides (continued) Symbol Three-letter One-lette r

Nucleoside

Nir

Ribosylnicotinamide Ribosylthimine

* Th d

Thiouridine

Srd

* dTh d * Ur d * Xa o

Thymidine (2'-deoxyribosylthymine ) Undine Xanthosine Phosphoric residu e

-P

«T

Sor sU

*d T *U *X p or _ b

a For computer work For interna l phosphodieste r bonds, use a hyphen .

Table 8. Symbols for Specific Preparations of Nucleic Acids. Thes e symbols may be used without definition . Name Symbol Complementary DNA , RN A cDNA Heterogeneous nuclear RNA hnRN Messenger RN A mRN Mitochondrial DNA, RN A mtDNA Nuclear DNA , RN A nDNA Ribosomal RN A rRN Transfer RN A tRN Chloroplast plasti d or DNA , RN A ctDNA

, cRNA A A , mtRNA , nRNA A A , pDNA , ctRNA, pRN A

Table 9, Buffers. Th e Buffe r name s ma y be use d without definition. Buffer name Systematic Description ACES 2-[(2-amino-2-oxoethyl)amino]ethanesulfoni c acid ADA [(carba18moylmethyl)imino]diaceti c acid BES 2-[bis(2-hydroxyethyl)amino)ethanesulfoni c aci d Bicine N,N-bis(2-hydroxyethyl)glycin e BisTris 2-[bis(2-hydroxyethyl)amino]-2-(hydroxymethyl)-propane-l,3-dio l CAPS 3-(cyclohexyIamino)propanesulfoni c acid CHAPS 3-[(3-cholamidopropyl)dimethylammonio]-l-propanesulfoni c aci d CHAPSO 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-l-propanesulfonat CHES [2-(N-cyclohexylamino)-ethanesulfoni c acid ] CDTA 1,2-cyclohexylenedinitrilotetraaceti c aci d EDTA ethylenediaminetetraaceti c acid

e

Continued

Plant Biochemistry 9

3

Table 9. Buffers (continued) Buffer name EGTA EPPS HEPES HEPPS MES MOPS PIPES TAPS TEMED TES Tricine Tris

Systematic Description [ethylenebis(oxyethylenenitrilo)]tetraacetic aci d Acceptable abbreviation fo r HEPPS (use HEPP S definition) . 4-(2-hydroxyethyl)-l-piperazineethanesulfonic acid 4-(2-hydroxyethyl)-l-piperazinepropanesulfonic aci d 4-morpholineethanesulfonic aci d 4-morpholinepropanesulfonic aci d 1,4-piperazinediethanesulfonic aci d 3-{[2-hydroxy-l,l-bis(hydroxyraethyl)ethyl]amino}-l-propanesulfonic aci d N,N,N',N'-tetramethylethyIenediamine 2-{ [2-hydroxy-l ,1 -bis(hydroxymethyl)ethyl]amino}ethanesulfonic aci d N-[2-hydroxy-l ,1 -bis(hydroxymethyl)ethyl]glycine 2-amino-2-hydroxymethylpropane-l,3-diol

Table 10. Tentative Rules and Recommendations of International Scientific Unions Group/Title General Abbreviations an d symbol s fo r chemica l names of special interes t i n biological chemistry. Abbreviations an d symbols : a compilation (1976). Citation o f bibliographi c references i n biochemical journals. Biothermodynamics Recommendations for the measurement and presentation of biochemical equilibriu m data. Recommendations for the presentatio n of thermody namic and related dat a i n biology (1985 ) Labeled compounds Isotopically modifie d compounds b Stereochemistry Fundamental stereochemistry c Enzymes Enzyme nomenclature . Recommendation s (1984 ) The nomenclatur e o f multiple forms o f enzymes Catalytic activity Units o f enzyme activit y (1978) Symbolism an d terminolog y i n enzyme kinetics Ami no acids, peptides, and proteins Nomenclature an d symbolis m for amin o acids and peptides. Recommendation s (1983)

May be found ina (1966) J. Biol. Chem. 241 , 527-53 3 (1977) Eur. J. Biochem. 74 , 1-6 (1973) J. Biol. Chem. 248 , 7279-728 0 (1976) /. Biol. Chem. 251 , 6879-688 5 (1985) Eur. J. Biochem. 153 , 429-43 4 (1978) Eur. J. Biochem. 86 , 9-2 5 (1979) Eur. J. Biochem. 102 , 315-31 6 (1970) J. Org. Chem. 25 , 2849-2867 (1984) Academic Pres s (1977) J. Biol. Chem. 252 , 5939-594 1 (1979) Eur. J. Biochem. 97 , 319-320 (1982) Eur. J. Biochem. 128 , 281-29 1 (1985) J. Biol. Chem. 260 , 14-4 2

Continued

94 Plant

Biochemistry an d Molecular Biology

Table 10. Tentative Rules and Recommendations (continued) Group/Title

May be found ina

Abbreviations an d symbol s fo r the descriptio n o f th e conformation o f polypeptide chains Nomenclature o f iron-sulfur proteins Corrections Nomenclature o f peptide hormone s Nomenclature of human immunoglobulin s Nomenclature o f glycoproteins, glycopeptides , an d peptidoglycans. Recommendation s (1985 ) Nomenclature o f electron-transfer proteins . Recom mendations (1989 ) Carbohydrates Tentative rules for carbohydrat e nomenclature . Par t 1. (1969) Corrections Conformational nomenclatur e fo r five- and six-membered ring forms of monosaccharides an d thei r derivatives (1980 ) Nomenclature o f unsaturated monosaccharide s (1980 ) Nomenclature o f branched-chain monosaccharide s (1980) Abbreviated terminolog y of oligosaccharide chain s (1980) Polysaccharide nomenclature (1980 ) Symbols for specifyin g th e conformatio n of polysaccharide chains Lipids The nomenclatur e of lipids. Recommendation s (1976) Nucleotidcs and nucleic acids Abbreviations an d symbol s for nuclei c acids, polynucleotides and their constituent s Corrections Abbreviations an d symbol s for th e descriptio n of conformations o f polynucleotide chains Nomenclature fo r incompletel y specified base s in nucleic acid sequences . Recommendation s (1984) Phosphorus Nomenclature o f phosphorus-containing compounds of biochemica l importance. Recommendation s (1976) Steroids The nomenclatur e o f steroids. Revise d tentativ e rulesd Amendments (1971 ) and correction s

(1970) J. Biol. Chem. 245, 6489-6497 (1979) Eur. J. Biochem. 93, 427-43 0 (1979) Eur. J. Biochem. 102 , 31 5 (1975) J. Biol. Chem. 250, 3215-3216 (1974) Eur. J. Biochem. 45, 5-6 (1987) J. Biol. Chem. 262,13-18 (1991) Eur. J. Biochem. 200, 599-61 1 (1972) J. Bio. Chem. 247, 613-634 (1972) Eur. J. Biochem. 25, 4 (1980) Eur. J. Biochem. 111, 295-298 (1981) Eur. J. Biochem. 119 , 1- 3 (1981) Eur. J. Biochem. 119 , 5- 8 (1982) J. Biol. Chem. 257, 3347-3351 (1982) J. Biol Chem. 257, 3352-335 4 (1983) Eur. J. Biochem. 131 , 5- 7 (1977) Lipids 12 , 455-46 8

(1970) J. Biol. Chem. 245, 5171-5176 (1971) J. Biol. Chem. 246, 489 4 (1983) Eur. J. Biochem. 131 , 9-1 5 (1986) J. Biol Chem. 261, 13-1 7 (1977) Proc. Natl. Acad. Sci. U.S.A. 74, 2222-223 0

(1969) Biochemistry 8 , 2227-224 2 (1971) Biochemistry 10 , 4994-499 5 Continued

Plant Biochemistry

95

Table 10. Tentative Rules and Recommendations (continued) Group/Title

May be found ina

Quinones Nomenclature o f quinones with isoprenoid sid e chains (1975 ) Eur. J. Biochem. 53 , 15-1 8 Carotenoids Tentative rule s for the nomenclature of carotenoids ( Revisione (1975 Cyclitols The nomenclature o f cyclitols. Recommendation s ( (1973) Folic acid Nomenclature and symbols for folic aci d and related ( compounds Corrinoids Nomenclature o f corrinoids (

) J. BioL chem - 247 > 2633-264 3 ) Biochemistry 14 , 180 3

1972

) Eur. J. Biochem. 57, 1- 7

1975

) Eur. J. Biochem. 2 , 5-6

1967

1974

) Biochemistry 13 , 1555-1560

Retinoids Nomenclature o f retinoid s (1983 Tetrapyrroles The nomenclatur e o f tetrapyrrole s Tocopherols Nomenclature o f tocopherols an d related compound s ( (1981) Miscellaneous (vitamins) Trivial name s o f miscellaneous compound s o f impor- ( tance i n biochemistry

) J BioL Chem. 258, 5329-533 3 (1980) Eur. J. Biochem. 108 , 1-3 0 ) Eu.r. J. Biochem. 123 , 473-47 5

1982

1966 J. BioL chem

)

Vitamin B6 Nomenclature fo r vitamin B6 and related compound s (

1973

Vitamin D Nomenclature of vitamin D (1981) (

1982

- 241 , 298 7-2994

) Eur. J . Biochem. 40 , 325-327

) Eur. J . Biochem. 124 , 223-22 7

a

Mos t of these documents have also been publishe d in other journals, e.g., Biochemistry, Biochem. J., Eur. J. Biochem., Boichim. Biophys. Acta, ARch. Biochem. Biophys. The secon d edition o f a Compendium of thes e documents is available from Portlan d Press Inc. , Ashgate Publishing Co., Ol d Pos t Rd. , Brookfield , VT 05036-9704; o r Portlan d Press, Ltd., P.O. Bo x 32, Commerce Way, Colchester CO2 8HP , Essex , U.K . Th e Pric e is £18.00/U.S. $36.00. Postag e is £2.00/U.S. $2.50 . A 15 % discount is allowable on order s fo r 1 0 copies or mor e to a single address. Paymen t must accompan y th e order. b Th e fina l versio n ma y be foun d i n (1979) Pure Appl Chem. 51, 353-380. c Th e fina l versio n may be found i n (1976) Pure Appl Chem. 45 , 11-30. d e

Th e definitive rule s for nomenclatur e of steroids may be found i n (1972 ) Pure Appi Chem. 31, 285-322. Th e definitive rule s ma y be found i n (1975) Pure Appl Chem. 41 , 407-431.

96 Plant

Biochemistry an d Molecular Biology REFERENCE

[Anonymous]. 1994 . Instruction s t o authors . Th e Journal of Biological Chemistry 269(1):777785. ©199 4 by The America n Societ y fo r Biochemistr y and Molecula r Biology, Inc. CONSULTANTS William H . Campbel l Dougla Michigan Tech . Universit y Universit Houghton, Michiga n Columbia

s D. Randal l y of Missouri , Missouri

Jan Mierny k Gregor USDA, ARS Universit Peoria, Illinoi s Athens

y Schmid t y of Georgi a , Georgi a

Jack Preis s Michigan Stat e Universit y East Lansing , Michigan

11 PLANT MOLECULAR BIOLOGY and GENE DESIGNATIONS Ellen M. Reardon an d Carl A Pric e Waksman Institut e Rutgers Universit y Piscataway, N J 08855-0759 1. TERMINOLOGY

The word s define d i n thi s sectio n represen t terminolog y commo n t o molecula r biology integrate d wit h certai n phrase s usefu l i n biochemistry , microbiology , an d genetics. A few terms are defined within other definitions; these are also printe d in boldfaced type . Word s i n italics ar e themselve s define d elsewhere althoug h italic s may also be use d fo r scientifi c names and eve n fo r emphases. 2D gel Two-dimensiona l gel ; an electrophoretic techniqu e based on runnin g a gel under one circumstance, e.g., a pH gradient, rotating the gel 90°, and rerunning the gel under differen t conditions . 35 S promoter A

strong promoter from cauliflowe r mosaic virus (CaMV).

amplified-fragment-length polymorphism (AFLP) A mapping. allele A

techniqu e use d i n genome

n alternat e form o f a gene at a specific locus.

anticodon A

nucleotide triplet complementar y to a codon.

ballistic transformation Th host.

e us e of a particl e gu n t o inser t foreig n DNA int o a

base, kilobase (b, kb) Adenin e (A) , guanine (G), cytosine (C) , thymine (T), an d uracil (U) . Base s ar e elements of DNA and RNA Th e lengths of DNA and RN A sequences are measured i n bases (100 0 b = 1 kb). branch point Th e poin t i n th e replicatio n o f a nucleotide chai n wher e ne w nucleotides are added . cauliflower mosaic virus (CaMV ) A centromere Regio attaches.

DNA virus that infects plants.

n o f th e chromosome to whic h th e mitoti c or meioti c spindle

97

98 Plant

Biochemistry an d Molecular Biology

chloroamphenicol transacetylase (CAT ) A as a reporter gene o r selectable marker. chromatin Th

bacterial enzyme encoded by cat; serves

e material o f chromosomes, consisting o f DNA and histone proteins .

chromosome A self-replicatin g modul e o f a genome consistin g o f DN A an d proteins. Note : nuclea r chromosome s ar e physicall y very differen t fro m chromo somes o f organelles and prokaryotes. Vira l chromosomes ma y be of DNA or RNA . circular A pofynucleotide chain , usuall y of DNA, in the for m o f a circle; 3 ' - and 5' -end s ma y be hydroge n bonde d o r joined covalentl y (see closed circular). cis Locate

d o n th e sam e stran d o f DNA .

closed circular A coding sequence A

covalently close d circl e o f DN A set o f codons that encod e a protein .

codon A ihree-nucleotide segment o f RNA specifyin g a n amin o aci d o r transla tional stop signal . colony A

grou p o f cells, normall y on a plate, derive d fro m a single cell.

colony hybridization A metho d fo r detectin g th e presenc e o f a specifi c sequence of DN A amon g bacterial colonie s o n a plate . compatibility Th e coexistence o f two genetic systems in the same cell or organism; e.g., phage with a host bacteriu m or organelles wit h a nucleus. complementary DNA (cDNA) A reverse transcriptase .

single-stranded DN A cop y of an RN A mad e by

complementation Th e rescue of function to produce a wild-type phenotype by two separate mutant s within the sam e cell; distinguishable from recombinatio n i n which a wild-type gene supplement s a mutation. constitutive Gene

s that ar e alway s expressed; housekeepin g genes .

construct A plasmid i n whic h geneti c o r structura l elements, suc h a s gene s o r restriction sites , ar e introduce d through artificia l means. controlling elements Sequence s tha t contro l th e expressio n o f genes b y inserting into o r retractin g fro m them ; transposable elements; transposons. cosmid Aplasmid plasmid DNA . cryo- Ver

includin g a lambda phage cos site that permits packaging of the

y cold conditions , a s in liquid nitrogen .

dalton, kilodalton (Da, kDa, kD) A uni t o f measuremen t o f molecula r mass ; kD=1000 daltons, wher e 1 dalton = 1.66 1 x 10- 24 g; equivalent t o th e unified atomic mass unit (u) , which i s an S I unit defined as 1/1 2 o f the mas s of an ato m o f 12 C. deoxyribonucleic acid (DNA) Th e macromolecul e in which genetic information is stored; th e primar y genetic materia l of all cells. domain A three-dimensional arrangement of amino acids with specific catalytic or binding properties .

Plant Molecular Biology an d Gene Designations 9 downstream

9

Proximal; in the 3' direction.

ectopic gen e A gene, usuall y on e transforme d int o anothe r species , tha t i s expressed i n other tha n it s normal locatio n o r stag e of development. editing Th e addition, removal, or substitution of nucleotides to a DNA or RNA to generate or restor e correct coding . electrophoresis Th e movemen t of a mixture of macromolecules into a semi-solid, porous mediu m i n respons e t o a n electri c fiel d t o determin e it s mass/charg e rati o (size) o r t o separat e i t fro m othe r components . Thi s techniqu e i s used t o separat e both protein s an d nucleic acids. ( A liquid medium can also be used, but toda y such applications ar e onl y for special purposes. ) electroporation Th foreign DN A

e openin g o f pore s i n cell s b y electric shoc k s o a s t o inser t

enhancer A DN A sequenc e ofte n bu t no t alway s dista l t o th e promoter tha t increases promote r activity , and therefore, transcription. exon Th

e codin g portio n o f an RN A transcript o f a split gene .

expressed sequenc e ta g (EST ) cDNA s for protein gene s that are expressed unde r selected conditions . ES T ofte n refer s t o a partia l sequenc e o f th e cDN A use d t o identify site s i n the genom e tha t encode a specific gen e product. expression, gen e expressio n Th e accumulatio n of specific gen e product s usually under define d environmenta l conditions . gel A semi-soli d mediu m int o whic h protein s o r nuclei c acid s ar e subjecte d t o electrophoresis, to determin e thei r size or to separate them from othe r components . gene Althoug h i t i s impossibl e t o "define " a gen e t o th e mutua l satisfaction of biochemists, molecula r biologists , and geneticists, in this context a concise meanin g might b e th e sequenc e of DNA tha t encodes a gene product (an RN A o r protein) , including al l upstream an d downstream sequences involve d in th e expression o f th e gene. gene famil y A se t o f gene s whos e sequence s diffe r onl y slightl y tha t encod e identical products ; within a single species, a multigene family. gene taggin g Th e additio n o f a marker t o a gene; often b y the introductio n o f a transposon o r insertio n element . gene transfer Transformation; th e insertion of foreign DN A into a host conferring a trai t no t previousl y inherant i n that organism. genome Su virus.

m o f al l geneti c informatio n of a n organism , nucleus , organelle , o r

jS-glucuronidase (GUS ) Bacteria l enzyme encode d by the uidA gene ; a selectable marker whose product can be directl y visualized in man y tissues. heat shock A n upwar d temperature shift inducin g stress that results in a quantitative or qualitativ e alteration in gene expression.

100 Plant

Biochemistry an d Molecular Biology

heterologous Perceive d a s different ; ofte n use d i n referenc e t o DN A t o mea n having dissimilar sequences. histone A smal l number o f highly conserved protein s tha t comple x with nuclear DNA to for m chromatin. homologous Perceive d a s having a common ancestor; ofte n use d i n referenc e t o DNA to mea n havin g similar sequences . hybrid duplex A double-stranded molecul e compose d of complementary DNA or RNA strands , o r singl e strand s o f complementar y DNA o r RN A fro m differen t species. hybridization Th hybrid duplex.

e matin g o f complementary DN A an d RN A strand s t o for m a

hydropathy plot A macromolecule.

ma p depictin g th e hydrophili c and hydrophobi c domains of a

immunodetection Th

e identificatio n of a specific polypeptide by use of antibodies.

induction Increase d expressio n o f a gene i n respons e t o a n externa l factor ; e.g. , expression o f the gen e encoding nitrat e reductas e in response t o nitrate ; see repression. insertion Introductio n of a nucleotide or nucleotide chain into RNA or DNA; may occur naturally , as by insertion element, transposon, o r T-DNA. insertional mutagenesis Chang e o f geneti c informatio n b y introductio n o f a nucleotide chai n int o a gene; gen e is usually rendered inactive . intron Non-codin ing.

g portion o f an RNA transcript tha t is removed during process-

iso-electric focusing (IEF) Separatio their isoelectric points .

n o f proteins i n a gradient gel to th e p H of

lariat A n intermediate structur e forme d i n an RNA molecule during the excision of certai n kind s of introns. lawn Th

e confluenc e of bacterial colonie s o n a Petri plate.

library Transforme d bacteria , cosmids , YACs , etc. , whos e inserts represen t th e entire genome (genomi c library) , or transcripts (cDNA library ) o f a n organis m expressed unde r define d conditions. ligation Th

e joining of insert and plasmid DNA, usually by the action of T4 ligase.

locus Sit e o n a chromosome at whic h a specifi c gene, or allele o f tha t gene , i s located. I n molecular term s a locus can be defined t o a single nucleotide, wherea s the precisio n o f a locus determined b y segregation analysis is limited to abou t 2 0 to 2000 kb or 1 centimorgan (se e morgan). megaplasmid A plasmid o f 10 0 k b o r more ; e.g. , ni f plasmids , which encod e enzymes o f nitroge n fixation .

Plant Molecular Biology an d Gene Designations 10

1

missense DNA Geneti c error resulting in a gene product with the wrong sequence. morgan (M ) A uni t tha t expresse s th e relativ e distanc e betwee n gene s o n a chromosome; one M equals a crossover value of 100 %; 1 centimorgan is equivalent to 2 0 to 2,00 0 k b in higher plants. Name d in honor o f Thomas Hun t Morgan . multigene family A set o f genes within a species tha t encode simila r or identica l products. mutation An y change i n the sequenc e o f DNA in a genome. nonsense DNA Geneti c error tha t result s i n premature termination of transcription int o RNA . northern blot Th e hybridizatio n on a membrane of a specific radiolabele d probe with RNA transferre d from a n electrophoretic separation . Note : northern blot is not capitalized; see Southern blot. nucleoid Regio concentrated.

n o f a prokaryote , plastid , o r mitochondrio n wher e DN A i s

nucleotide Th e basic subunit of DNA and RNA, composed o f a base (A, T or U , G, C), a sugar (deoxyribose or ribose), an d a phosphate . nucleus Th matin.

e portio n o f the cell , often membrane bound, that contain s the chro -

palindrome Inverte d repeat s o f DN A suc h tha t th e sequenc e i s the sam e when read forwar d o r backward ; e.g., CAGTTGAC , o r i n the English language, "Madam, I'm Adam. " phage A

virus that infect s bacteria .

phenotype Th e displa y of characteristics exhibited by an organis m resulting fro m the expressio n o f its genome in the existin g environment. plaque Clearin bacteriophage.

g o f bacterial lawn caused by a virus infection initiated by a single

plaque-forming unit (PFU ) A quantitativ e measur e o f th e numbe r o f viruse s descended fro m a single colony require d t o clear a n area o f a bacterial lawn. plasmid DN A that can replicate independently within a bacterial cell; engineere d plasmids serv e as cloning vectors fo r the insertio n of foreign DN A into a host. plating Growin g bacterial colonies , transforme d or otherwise , on a Petri plate . ploidy Th e number s of copies o f a genome found i n a given species; haploid has one copy ; diploid, two; etc . polyadenylation Th e post-transcriptional addition of adenylates to the 3' - end of a mRN A molecule ; poly(A) + an d poly(A) " refe r t o th e presenc e o r absenc e o f multiple A residues. polymerase Th

e enzym e by which DNA and RNA ar e replicated fro m a template.

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Biochemistry and Molecular Biology

polymerase chain reaction (PCR ) A reactio n i n whic h a templat e o f DN A i s elongated b y cycling of temperature s i n a reactio n chambe r with primer(s) an d al l possible nucleotides i n excess . polynucleotide A

chain o f nucleotides; DN A or RNA .

post-transcriptional regulation Regulatio n o f gene expression afte r th e synthesi s of th e primar y transcript, a s at th e leve l o f processing or degradatio n o f transcripts. post-translational regulation Contro l of gene expression afte r translation, as at th e level o f processing o r degradatio n o f proteins . premature termination Terminatio n o f transcription befor e the en d o f the coding sequence resultin g i n an incomplet e transcript . primary transcript A n RN A synthesized directly fro m it s DNA template prio r t o processing, polyadenylation , o r editing . primer Short , single-strande d nucleotid e segmen t tha t initiate s th e replicatio n o f DNA fro m a template . probe A DNA, RNA, or protein use d to identify o r isolate a specific target DNA , RNA, o r protein . promoter Th e region o f DNA that binds RNA polymerase II to initiate transcription; promoters ma y be constitutive o r "turned on" in response to a variety of signals. See signal transduction. protein structure: primary (1° structure) Th

e amino-acid sequence of a protein .

protein structure: secondary (2° structure) Th e loca l conformation or foldin g of the protein' s backbone, a s into helice s or pleated sheets . protein structure: tertiary (3° structure) Th a protein .

e three-dimensiona l organization of

protein structure: quarternary (4° structure) Th e organization of some protein s from multipl e polypeptid e subunits . Homopolymeric proteins ar e compose d o f identical subunits; heteropolymeric proteins ar e compose d o f dissimilar subunits. pseudogenes A gen e rendere d non-functiona l b y additio n o r deletio n t o it s structure; probabl y related t o duplicate d genes . pulsed-field electrophoresis Th e separatio n o f genomic, or very large DNAs i n a semi-solid mediu m b y electric pulses rather tha n constan t current . random-amplifled-polymorphic DNA (RAPD) Th e amplificatio n of sequence s o f DNA distribute d randoml y throughou t a genom e b y PC R technolog y t o analys e genetic structur e o r relatednes s o f populations . reading frame A polypeptide.

specific mode of reading codon triplet s t o produc e a functional

receptor Recipien t o f a signal, such as a hormone , protein, light, etc., tha t binds to a specific site an d initiate s a reaction. Se e signal transduction.

Plant Molecular Biology an d Gene Designations 10

3

recombinant A n organism whose genetic makeup is altered by the stable insertion of a foreign DNA . regulation Contro

l o f gene expression.

reporter gene Th e codin g regio n o f a surrogat e gen e whos e produc t i s easil y observed, eg. , CAT , GUS , LacZ , fuse d t o th e promote r o f a nativ e gen e whos e product i s difficul t t o detect . Demonstratio n o f th e surrogat e gen e analyze s th e native gene: its function, localization, an d responses to developmental an d environ mental signals. repressor Negativ e regulatio n o f a gen e i n respons e t o a n externa l factor ; e.g. , decreased expression o f the gene encoding nitrate reductase in response t o ammonium; see induction. restriction enzyme A n enzyme , usuall y of bacteria l origin , tha t cut s DN A a t specific base pairs, producing restriction fragments. restriction-fragment-length polymorphism (RFLP) Characterizatio by comparison o f sizes o f selected restriction fragments.

n of a genome

Ri plasmid Plasmi d o f Agrobacterium rhizogenes; plasmi d confer s "hairy-root " pathogenicity to Agrobacterium species. ribonucleic acid (RNA) A polynucleotide in which the sugar is ribose rather tha n deoxyribose; th e molecule o f which messenger-, ribosomal-, and transfer-RNAs, and some viral genomes ar e composed . RNA editing Th e substitution , additio n o r remova l o f base s i n a transcript t o produce a "correct" transcript . scoreable marker A

trait tha t ca n be identifie d in a bacterial lawn .

second messenger A small molecule within a cell that relays a chemical messag e from outsid e the cell , a s cyclic AMP. selectable marker A trait whose presence or absence enables one to grow colonies or organisms with or without a specific essential component; e.g., antibiotic-resistan t mutants in the presence o f that antibiotic, or in the absence of an otherwise essential nutrient. selection Identificatio

n o f a specific trait usefu l i n singling out a transformant.

selective amplification of microsatellite polymorphic loci (SAMPL). A nique use d i n genome mapping .

PCR tech -

sequence A specific string of bases in a protein o r polynucleotide . A s a verb, t o sequence means t o determin e th e sequence s o f amino acids in a protein o r bases i n a polynucleotide . signal sequence, signal peptide A portion , usuall y th e N-terminus , of a protei n that is recognized and removed co-translationally by the endoplasmic reticulum (ER) prior t o transpor t o f the protei n int o the lume n of the ER ; se e transit peptide. signal transduction Th e proces s b y which th e perceptio n o f a n externa l signa l induces a result: th e expression of a gene or set of genes; e.g., the steps between th e

104 Plant

Biochemistry an d Molecular Biology

absorption o f ligh t b y phytochrom e an d th e synthesi s o f protein s o f th e light harvesting complex . sodium dodecyl sulfate (SDS ) A detergen t use d t o separat e polymeric , o r apoproteins into thei r monomeric subunits . Se e protein structure: quarternary. Southern blot Transfe r o f DNA tha t ha s been separate d b y electrophoresis to a membrane i n order to probe it by hybridization; after E.M . Southern. I n recognitio n of Southern's contribution , subsequent researcher s name d RNA or protein blots after directions also . Se e northern blot, western blot. spliceosome A comple x o f macromolecules tha t remove s introns and joins exons during RNA processing . splicing Th

e joining of exons into a mature mRNA . gene interrupte d b y an intron, or non-codin g sequence .

split gene A

stop codon A codon tha t cause s terminatio n o f transcription; specificall y UAA , UAG, and UG A subtraction library A library of cDNAs containing only those transcripts expresse d under a defined condition afte r eliminatio n of transcripts from differin g conditions . suppression Th sequences.

e phenotypi c correction o f a mutation without changing any gene

T-region of Ti plasmid Th genome. telomere Sequence replication.

e portion of a Tiplasmid that is transferred into the host

s at both termin i of each eukaryotic chromosome that facilitate

temperature-sensitive mutation On e i n which a wild-type phenotype is expressed at the permissive temperatur e and a mutant phenotype at a non-permissive (usually higher) temperature . template Th e stran d o f DN A o r RN A tha t serve s a s th e mode l fo r it s ow n replication o r transcription . Ti plasmid Plasmi d o f Agrobacterium tumefacien s tha t confer s pathogenicit y i n crown-gall infection . trans O

n th e opposit e strand o f DNA; see cis.

transcript A

n RN A tha t i s copied (transcribed) from a gene .

transcription Generatio transduction Introductio transformation Th of a n organism .

n o f an RN A cop y of a DNA sequence . n o f foreig n DN A int o a genome by a phage vector.

e introduction of a gene previously not inherent in the genome

transient gene expression Expressio integrated int o a genome .

n of a foreign or ectopic gene that has not been

Plant Molecular Biology an d Gene Designations 10

5

transit peptide Th e N-terminus of a protein tha t is recognized post-translationall y and (usually ) removed durin g transport o f a protein acros s a membrane; se e signal peptide. translation Formatio amRNA

n o f a protein o n a ribosome accordin g to the instructions in

transon Exons encode d separatel y fro m on e another , with other gene s betwee n them o r on opposite strands. transposition Th

e insertio n o r excisio n o f a transposon t o o r fro m a genome .

transposon A transposable elemen t usually flanked by inverted repeat sequences; see controlling elements. twintron A

n intron within another intron .

upstream Dista downstream. vector Plasmid;

l or 5' t o the promoter; opposite th e direction of transcription; see means of introducing foreign DNA int o a host .

western blot Immunodetectio n o f proteins blotted t o a membrane. Note : western blot i s not capitalized ; se e Southern blot. yeast artificial chromosome (YAC) A construct including centromere, telomeres, an origin o f replication an d multipl e cloning sites fo r the insertio n o f foreign DNA . 2. GENE DESIGNATIONS

Any discussion o f gene nomenclature mus t be prefixed with the subject to which th e terminology i s to be applied: specifically , the traditiona l genes of genetics and plant breeding, contraste d wit h genes tha t hav e been clone d an d sequenced . A. Nomenclatures of traditional genetics. A specifi c locus o n a chromosom e that i s associate d wit h a uniqu e phenotyp e wil l be referre d t o her e a s a geneti c system base d on segregational analysis. Segregationa l nomenclature s fo r individua l plant specie s ar e distinct , an d ther e i s n o systemati c effor t t o assig n commo n designations t o simila r gene s i n multipl e plants. Mutant s with similar phenotypes may have no similarit y at th e molecula r level; they can only be distinguished on th e basis of their loci on chromosomes. Thre e maize mutants with shortened internodes , for example , migh t b e calle d dwarf1 , dwarf2 , an d dwarf3 . Year s late r i t migh t b e discovered tha t dwarfl i s due t o a lesion i n the biosynthesi s of giberellin, dwarf2 t o a defec t i n a recepto r fo r gibberellin , an d dwarf 3 du e t o som e totall y unrelate d process. A dwarf mutant in arabidopsis might be due to the same lesion in giberellin biosynthesis, bu t geneticist s ca n not affor d t o wait until the biochemical functio n of the gene product has been determined before designations ar e assigned t o the genes. B. Nomenclature of sequenced plant genes. Th e Commissio n on Plan t Gen e Nomenclature (CPGN) was founded i n 1991 under the auspices of the International Society for Plant Molecular Biology. Th e goal of the CPGN is to unify nomenclature across th e plan t kingdom : a gen e encodin g nitrat e reductas e i n tomat o o r i n arabidopsis or i n pe a would have the same name. Th e establishmen t of plant-wide

106 Plant

Biochemistry an d Molecular Biology

designations, a uniqu e developmen t i n biology, i s aided b y a lon g tradition amon g plant scientist s o f sharing ideas regardles s o f the specie s unde r study. Once a gene ha s been isolate d an d sequenced, w e can make comparisons with genes fro m othe r organisms . A common nomenclatur e fo r sequenced plan t gene s began i n 198 3 wit h a proposa l fro m Hallic k an d Bottomle y fo r designation s fo r chloroplast genes , no w univerally adopted. I n 198 8 Lonsdal e an d Leaver propose d a uniform terminology for mitochondrial genes. CPG N extended the basic principles to al l sequenced plan t gene s (CPGN , 1994) . C. Gene families. Th e guidin g principle o f the CPG N nomenclature i s that all genes throughout the plant kingdom that encode the same product are members of the same gene family, (cf . Fig. 1) . Th e same product means that if the sequence s o f two products are identical , the y are obviously the same. Bu t small differences in coding sequences commonl y occur within and among species, as in RbcS genes, such that th e products-the small subunits of ribulose-bisphosphate carboxylase-may be very similar but ar e no t identical . Thes e slightl y different smal l subunits are nonetheles s per ceived a s being "the same" and a s belonging to a single, plant-wide family o f genes . There ar e man y instance s wher e gene s ar e classifie d furthe r o n th e basi s o f sequence; e.g., four distinguishabl e sequence s encod e functionall y identical larg e subunits o f ADPglucose synthase , and fou r distinguishabl e sequences encod e func tionally simila r superoxid e dismutases. Fo r gene s encodin g both set s o f proteins , coding sequences withi n a set of genes are 80 to 90 %, but may be only 50 % similar among sets, both within and among species. The requiremen t fo r simila r codin g sequence s i s no t absolute . Protein s dis playing activitie s o f 1-aminocyclopropane-l-carboxylat e oxidase , fo r example , ar e encoded b y gene s wit h a variet y o f codin g sequence s tha t d o no t fal l int o an y discernible natura l groupings . I t seem s reasonabl e i n suc h case s t o assig n thos e genes, a t leas t fo r the present , t o a single family . D. Gene families and multigene families. Multipl e gene s tha t belon g t o th e same plant-wide gene famil y within a single species comprise a multigene family. Thi s is consistent wit h conventional usage . Differen t member s of multigene families ar e distinguished by member numbers, based generall y on th e chronolog y of isolation . E. Gene designations. A specifi c gen e in an individua l species o f plant is full y defined b y four fields : Membership i n a plant-wide gene famil y Species o f plant Genome (nuclear , chloroplastic , mitochondrial, viral) Membership in a multigene family The gen e symbo l identifying memberhi p in a plant-wid e gene famil y i s usuall y three letters followed by a number, such as Adh1 or Gln2, but mor e letters ma y be used a s needed. Th e letter s can be followed by a capital letter instea d of a number where dictated b y prior usag e or b y homology with bacterial genes, such as RbcS o r TubB. Nuclear-encoded gene s alway s star t wit h a capita l letter, a s i n th e example s above, while genes encoded i n chloroplasts or mitochondri a start with a lower-case

Plant Molecular Biology an d Gene Designations 10

7

letter, such a s rbcL or cox2. Thus , th e gen e encoding the smal l subunit of ribulosebisphosphate carboxylas e i s RbcS i n higher plant s but rbcS i n chromophytic algae. The fou r field s denotin g a gen e shoul d b e state d explicity . A n abbreviate d format ca n als o b e use d provide d i t i s defined i n advance. Th e thir d membe r o f a multigene famil y in A. thaliana, encoding th e light-harvesting complex type I LHCII, for exampl e (cf . Fig. 1) , could b e represente d a s Lhcb1;At;3 . F. Public Databases of Plant Genes. Detaile d informatio n o n gene s i n a number o f plan t specie s ar e availabl e throug h a maste r database , PGD, whic h i s maintained b y th e Nationa l Agricultura l Librar y o f th e USDA . Th e specie s represented i n PGD includ e A. thaliana, maize and other grains , an d soybean, an d are bein g incremente d o n a n almos t dail y basis . PG D als o contain s th e CPG N listings o f sequenced plan t genes . Th e electroni c addres s o f PGD is: http://probe.naiusda.gov:8300.html

Fig. 1. Designations for plant-wide gene families. Th e CPG N classifies sequenced plan t genes into families based primarily on the functio n o f the gene product . I n this example of the light-harvesting complex typ e I LHCII, every gen e i n the plan t kingdom encoding this protei n i s a membe r o f thi s gene famil y an d bear s th e gen e symbo l Lhcbl. Th e ISPMB number i s a consecutivel y applie d identification numbe r use d i n the management o f the CPG N databases. Gene product numbers ar e part o f a numerical system being developed b y the CPG N for the classification o f related familie s of genes analogous t o Enzyme Commission numbers. Specifi c gene s in individual species of plants ar e identified b y a name or mnemonic o f their plant-wide gene family, the genus and species of the plant, and member numbers, representative o f thei r occurrence in multigen e families .

108 Plant

Biochemistry an d Molecular Biology References

CPGN. 1994 . Nomenclatur e o f Sequenced Plan t Genes . Plan t Mol. Biol . Reptr . 1 2 Supplement: S1-S109. Hallick, R.B. 1989 . Proposal s for the naming of chloroplast genes. II . Updat e to the nomenclature of gene s fo r thylakoi d membran e polypeptides . Plan t Mol. Biol. Reptr. 7:266-275 . Hallick, R.B., an d W . Bottomley. 1983 . Proposal s for the namin g of chloroplast genes . Plan t Mol. Biol. Reptr . 1:38-43 . Jansson, S. , E. Pichersky , R. Bassi , B.R . Green , M. Ikeuchi, A. Melis , D.J. Simpson , M . Spangfort, L.A. Staehelin , an d J.P . Thornber . 1992 . A nomenclatur e fo r th e gene s encodin g th e chlorophyll a/b-bindin g protein s o f higher plants. Plan t Mol. Biol. Reptr . 10:242-253. Lonsdale, D.M. an d C.J . Leaver. 1988 . Mitochondria l gene nomenclature. Plan t Mol. Biol. Reptr . 6(2):14-21. We ar e indebte d t o th e authoritie s wh o compris e ou r mor e tha n sixt y working group s fo r th e development o f CPGN's commo n nomenclatur e for sequenced plan t genes. Withou t their expertis e and continuing input, we would b e unable to make databases o f approved designation s for sequence d plant gene s availabl e to th e scientifi c public, and without charge.

Consultants for Section 1 Sewell P . Champ e Eri Waksman Institut e Coo Rutgers Universit y Rutger Piscataway, Ne w Jersey Ne Frank B. Salisbury Juli Utah Stat e Universit y E.I Logan, Uta h Experimenta

c La m k Colleg e s University w Brunswick, New Jerse y e Vogel . D u Pont d e Nemours & Co., Inc. l Station Wilmington, Delawar e

IV PLANT GROWTH AND DEVELOPMENT The physica l an d chemica l processe s i n plant s tha t for m th e basi s fo r th e units , symbols, an d term s presente d i n th e previou s section s al l tak e plac e i n th e highly complex machiner y tha t w e recogniz e a s a livin g organism: th e roots , stems , an d leaves wit h their xyle m an d phloem, parenchym a and pith, and all the othe r tissue s made up of cells that in turn are highly complex machines with their cytosol, nucleus, and sundry organelles. Thos e physical and chemica l functions are targets fo r much study i n plan t physiology , bu t th e trul y astoundin g thin g abou t livin g organism s including plants i s that the y are sel f generating. Al l that machiner y comes fro m a single cell , the zygote . Discoverin g ho w this happens i s the goa l o f studies i n th e subfields o f plant growt h and development. Thi s section attempt s to assembl e th e terms, symbols, and unit s of measurement used by researchers i n those fields. Most growt h an d developmen t i s influenced , sometimes strongly , b y changin g environmental factors . Thi s is obvious in the case of the tropisms and the induction of reproductiv e growth , but i t ma y be a little les s obvious in some other case s such as responses to salinity or chilling stress . This section s begin s wit h terms an d unit s that describ e th e change s i n siz e an d complexity tha t w e recogniz e a s growt h an d development , continue s wit h plan t movements an d reproduction , an d the n present s a larg e chapte r wit h subsection s based o n plan t response s to various stress factors.

12 MORPHOGENESIS AND THE KINETICS OF PLANT GROWTH Ralph O . Erickson1 Department o f Biolog y University of Pennsylvani a Philadelphia, Pennsylvani a 1910 4 U.S.A . This chapte r deal s wit h terms used i n studying the kinetic s of growth. A few terms are defined within other definitions; these are also printed in boldfaced type. Word s in italics ar e themselve s define d elsewhere ; italic s ar e als o use d fo r symbol s tha t represent physica l quantities (a s in the res t o f this book) . 1. THE BIOMETRY OF GROWTH. absolute growth rate Rat e o f chang e o f x (size ) wit h respec t t o t (time) , dt/dt ; dimensions o f x t- 1 (e.g. , m m d- 1). Whe n th e rat e i s approximately constant fo r a period o f time, growth i s then terme d linear. allometry Simpl e allometr y obtain s when the relativ e growt h rates o f two measured attribute s o f a n orga n o r organism , y an d x, ar e i n a constan t proportion . Formulated a s y = ax k, log y = log a + klogx, wher e a i s a constan t an d k i s th e allometric coefficient; dimensionless. anisotropic Havin

g differen t propertie s alon g different directions .

anisotropic growth Magnitud

e of growth vector differ s i n different directions .

autocatalytic growth function (or curve) function. Th e transformation ,

a symmetrica l sigmoi d is linea r an d ca n b e use d t o

evaluate a an d k graphicall y or b y least square s fo r given data o n x vs. t. cell production rate Loca

l rate o f formation of new cell walls.

convective rate of change Rat e of change associated with movement of a particle to a new location i n the growt h field . deposition rate Loca l net rate of production or import of a metabolite; where p i s density, t is time, and u is growth velocity. 1Current address is: Ralp h O . Erickson , 192 0 Dog Kennel Road , Media , PA 1906 3 111

112 Plant

Growth and Development

determinate growth Obtain s whe n the approximate maximum size of an organ o r organism i s determined, presumedl y genetically, a s in the growt h of a leaf. Growt h curve i s usually sigmoid. exponential growth function (or curve) Assumin g that the relativ e rate of change ofx wit h t, r=dlnr/dt, i s constant, x=aert, or lnx=lna+rt. Plottin g Inx against t gives a straigh t line , fro m whic h a and r may be estimated . growth Increas e in a measured attribute , x, of an organ or organism, as a function of time, t ; x = f(t). growth field Representatio n of the spatial distribution of a developmental variable . growth velocity v x; rate of displacement o f a material particle locate d at x. indeterminate growth Obtain s whe n growth is potentially not limite d (excep t by external factors) , as is often th e cas e with apical growth of a root o r shoot . kinematics Th e stud y o f motion and shape change, apar t fro m consideration s of mass and force . local derivative Rat e of change associated wit h a spatial location; e.g. , the rat e of change o f the positio n 3 mm from th e ti p of the root . logistic function Sam e a s autocatafytic growth Junction. material derivative Rat e o f chang e associate d wit h a real , o r material , plan t element. monomoleculargrowth function (or curve) x = a(l - e' kt); represent s increase of a measure d attribute , x, at a decreasin g rate , to a maximu m value , a. The linea r transformation, ln(a - x) = In a - kt, allow s graphical or least-square s estimation o f a an d k fro m dat a o n x vs. t. relative elementa l growth rat e (RELEL) Fo r growth along an axis, x, for growt h of a surface, referred to coordinates , x, y, the growt h RELEL tensor i s used; REGR

dimension, t-1.

relative growth rat e Rat e of change relative t o x with respect t o time and proporMay b e symbolize d r; dimension , t- 1. Whe n r i s tional t o approximately constan t to r a period o f time, growth is then terme d exponential . Richards growth functio n (o r curve ) x = a(l ± be-kt)1/(1-m; take s a variety of asymmetrical sigmoi d forms . Th e transformation , I n ((x)1-m + 1) = In b - kt , i s a

linear fo r appropriate choic e o f sign, a and m, an d can be used to evaluate b and k , from give n dat a o n x vs. t. A computer solutio n i s advisable. sigmoid growt h curv e A plo t o f a measured attribute, x, agains t time, t, showing an early phase of acceleration, an d later a deceleration phase, approaching a limiting value.

Plant Growth and Morphogenesis 11

3

2. SHOOT AND ROOT MORPHOGENESIS apical cell Th e singl e initia l presen t i n th e apica l meriste m o f som e root s an d shoots, as in many lower vascular plants. Divide s to form a segment cell merophyte, and a successor apical cell; this process usuall y occurring periodically. decussate O f leaves on a stem, arranged in pairs at each node, each at right angles to th e nex t pair abov e o r below . Symbol , 2(1,1). development Chang differentiation Increas

e fro m on e patter n o f growth to another . e i n histological complexity.

divergence angle Inphyllotaxis, th e difference i n angular position of two successive leaves o n a stem, primordia a t the shoo t apex , scales o n a cone, etc . Fibonacci sequence Th e integer sequence, 1 , 1, 2, 3, 5, 8, 13, . . ., in which each term (after th e firs t two ) i s th e su m o f th e precedin g tw o terms . Ther e ar e relate d sequences, suc h as the Lucas sequence, 1 , 3, 4, 7, 11, . . .(See phyllotaxis). generative helix or spiral Th e sequence of leaves on a stem, or of primordia at th e shoot apica l meristem , numbered i n order o f distance along the axis , or i n order of radial distanc e fro m th e cente r o f the meristem . Ther e ma y be one or more spirals in k-jugate phyllotaxis. growth zone Tha t portio n o f a root , shoot, o r othe r structur e in which cells ar e formed an d enlarge . initial (1 ) A meristemati c cell tha t divides to for m a new initial cell, plu s a cell that divide s furthe r t o ad d cells t o th e plan t body; (2) a meristemati c element tha t differentiates int o a mature specialized element , as a metaxylem initial. intrusive growth Tha t type of growth in which the growing cell penetrates between existing cells and in which new areas of contact ar e formed betwee n the penetratin g and neighborin g cell s (cf . symplastic growth). leaf plastochron index (LPI) Indicate s th e developmenta l age of a leaf; fo r a leaf with seria l numbe r i , LPI = P I - i . Whe n th e lengt h o f a lea f i , Li, equal s th e reference length , Lr, the n LPI = 0. meristem Tha t portio n o f a growt h zone i n whic h cel l formatio n (cell division ) occurs, accompanie d b y cell enlargement. parastichy Inphyllotaxis, a helical or spira l rank of leaves or scale s along a stem, or aroun d th e cente r o f a shoot apica l meristem; e.g., a 3-parastichy passes through every third leaf along th e stem . phyllotaxis Th e arrangement of leaves on a shoot, of primordia at the shoot apical meristem, o f scale s o n a pine cone , etc. ; formulate d b y citin g a pai r o f oppose d parastichies connecting neighborin g leaves that differ i n serial number by integers, m and n; symbol (m,n). Thes e integers are often consecutiv e terms of the Fibonacci sequence, as (3,5). Wher e whorls of k leaves occur at each node, the symbol is k(m,n).

114 Plant

Growth and Development

plastochron (1 ) The period of time between the commencement of two successive, repetitive processes, a s between th e initiation s o f two successive leaf primordia ; (2) by extension, th e tim e perio d betwee n correspondin g stage s o f development o f two successiv e leaves . plastochron ratio (a) (1 ) At the shoot apex, a = rn/rn+l, where rn is the radial distance fro m th e ape x to the cente r o f a leaf primordium n , and rn+1, i s the distanc e to th e nex t younger primordium ; (2 ) more generally, the rati o o f a measured attri bute of two successive leave s o f a growing shoot, as, for leaf length (L), a = L n/Ln+l. plastochron index (PI) Indicate

s comparativ e developmenta l ag e of a shoot :

, where L i s leaf length, Lr i s reference leaf length (e.g. , L, = 1 0 mm), and n is serial number of the leaf just longer than Lr. Assume s leaves are growin g exponentially with equal relative rates, and plastochron is constant. relative plastochron growth rate Relative growth rate o f leaves or lea f primordia , regarding time as measured in plastochrons; p = ma, where a is the plastochron ratio; dimension, t- 1, where t is measured i n plastochrons. steady growth A s i n a root , growt h in which the patter n of cell productio n an d enlargment i s invarient with time. symplastic growth Adjacen t cel l walls do not alter thei r position relative t o each other, and no new areas of contact are formed; this leads to expansion with minimum shear i n the cros s section . CONSULTANTS Peter W . Barlo w University o f Bristo l Bristol, Englan d

R.F. Lyndo n University of Edinburg h Edinburgh, Unite d Kingdo m

P.W. Ganda r Plant Physiolog y Division , DSI R Palmerston North , Ne w Zealan d

T. Sach s The Hebre w Universit y of Jerusale m Jerusalem, Israe l

Paul B . Gree n Stanford Universit y Stanford, Californi a

Frank B . Salisbury Utah Stat e University Logan, Uta h

Zygmunt Hejnowic z Silesian Universit y Katowice, Polan d

Wendy Kuhn Silk University of California Davis, California

Aristid Lindenmaye r University of Utrecht Utrecht, Netherland s (deceased 1989 )

R.F. Williams Australian Nationa l University Canberra City , Australia

13 GROWTH ANALYSIS AND YIELD COMPONENTS Bruce G. Bugbe e Plants, Soils and Biometeorolog y Departmen t Utah Stat e Universit y Logan, Uta h 84322-482 0 1. GENERAL CONSIDERATIONS

Plant growt h analysi s values an d yiel d component s ca n easil y and convenientl y b e expressed wit h S I units, an d yet S I units are ofte n incorrectly used t o repor t thes e measurements. Lik e many units reported in the literature, the reasons are historical. A majo r reference boo k o n th e subjec t of plant growth analysis (Hunt, 1982 ) use d metric and not S I units. However , a recent updat e of this book (Hunt , 1990) i s now consistent with SI rules, except for the use of non-base units in the denominator (mg, weeks), which could b e avoided (se e Chapter 1) . Th e widespread use of the hectar e as a unit of area ha s caused thi s unit to remai n allowable in many applied agricultural journals, but its use creates a communication barrier between basic and applied researchers tha t could be resolve d i f both groups used th e S I unit for area: m2. The mos t problematic growth analysis parameters are those with a unit of time in the denominator . Unlik e measurements that integrate plant physiological func tions ove r a shor t tim e interva l (seconds) , growt h analysis measurements typically integrate the results of many physiological functions over days or weeks. A measured carbon exchang e rat e would be expressed with SI units as mol m- 2.s-1 with positive values durin g the ligh t perio d and negativ e value s durin g the dar k period . The integrated result o f the diurnal carbon flux, th e crop growth rate, is typically expressed a s kg.m-2.d- 1. Thi s uni t i s no t strictl y allowabl e according t o som e author s because o f th e us e o f day s i n th e denominator , bu t th e correc t unit , kg.m-2.s-1, does no t indicat e th e tim e o f da y when th e integratio n occurred. Despit e thes e problems, th e recommende d tim e interval is day for crop growt h rate. Th e us e of days in the denominator is also important when expressing integrated daily radiation flux (se e Chapte r 9). Hun t (1990 ) argues that some biological processes need t o be integrated ove r lon g interval s an d thu s use s week s i n th e denominato r o f som e growth analysi s units . Th e us e o f week s a s a uni t o f tim e i s no t recommended . Unlike a 24- h interval, a 7-d interval ha s no special significanc e to a plant. Whe n measurements are mad e at weekly intervals, the results should be reported as a daily average. Thi s avoid s the confusio n of an additiona l unit o f time. 115

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Specific leaf area , a common growt h analysis measurement, ha s historically been reported a s cm 2 g- 1. Th e us e o f thi s uni t resulte d i n a rang e o f number s fo r th e parameter between abou t 5 0 and 300 cm2 g-1, but the gram is not an SI base unit and its us e shoul d b e avoide d i n th e denominator . Th e bas e uni t i s the kilogram , kg. Presumably in an effort t o utiliz e SI units, specific leaf area ha s been reporte d a s m2 g-1, whic h result s i n a very small rang e o f values fo r th e paramete r (betwee n 0.00 5 and 0.030). Th e preferre d unit , m 2 kg- 1, results i n a range of values between 5 and 30; it shoul d therefor e b e used t o expres s specifi c leaf area . 2. UNITS FOR GROWTH ANALYSIS AND YIELD COMPONENTS The following are some examples of preferred units for reporting growth analysis measurements an d yield components . Remembe r tha t denominator s shoul d b e SI base units, wit h th e exceptio n o f time wher e da y is accepted. Numerator s wit h o r without prefixe s ca n b e use d s o tha t th e rang e o f values wil l be betwee n 0. 1 and 1000. Th e followin g example s sho w th e bas e unit s i n bot h numerator s an d denominators, a s is customary when showing SI units. Table 1. Terms and Units for Plant Growth Parameters relative growth rate or specific growth rate

kg.kg-1.d-1 (g i s appropriat e fo r th e numerator ; g.g-1.d- 1 i s the uni t most ofte n used , bu t i t i s not recommende d becaus e i t uses g, a non-Si bas e uni t i n the denominator )

net assimilation rate

kg.m-2.d-1 ( g is appropriate fo r th e numerator) .

leaf area ratio

m2.kg-1 (m 2.

1

2

lea f area pe r k g total dr y biomass) .

2

lea f are a pe r k g leaf dry mass).

specific leaf area

m kg- (m

specific leaf mass

(the invers e of specific lea f area, ofte n calle d kg.m -2 specific lea f weight).

leaf mass ratio

kg.kg-1 (k

crop growth rate

kg.m-2.d-1 ( g is appropriate for th e numerator ; it places th e typical rang e of values between 1 and 100) .

seasonal crop yield

kg.m-2

harvest index

The ratio of harvested or edible (usable) biomass to total biomass or to above-ground biomass. Th e convention used must be specified. A s a ratio , harves t inde x i s dimensionless ; i t ca n b e expressed a s a decima l fraction o r a s a percen t (b y multiplyin g the fractio n b y 100) .

nutrient concentration in plant tissue (N, P, K, etc.)

mol kg- 1. Thi s is typically expressed a s a percent, g.kg- 1, or a s ppm. g.kg- 1 i s a correc t Si-unit , bu t inorgani c element s ar e pure substances, and thei r concentratio n is thus better expresse d as mole s rathe r tha n a s mass . Expresse d o n a mas s basi s i t appears that N an d K are a t simila r level s in plant tissue; i n fact , the numbe r of N atoms is about 3 times higher tha n the number of K atoms. Th e physiologica l importanc e o f nutrient s i s determined b y their number , not thei r mass.

g lea f mas s per k g total dr y biomass).

Growth Analysis and Yield Components 111 Other compound units are use d in plant growth analysis and yield. Adherenc e to SI rules should be made with the exception of the use of days in the denominator for som e compoun d units . Note agai n tha t th e bes t uni t of area i n the denominato r is the squar e meter. If th e magnitud e of values i s above 999 or belo w 0.1, th e valu e of the uni t in th e numerator shoul d b e change d b y adding or deletin g the appropriat e prefix . Fo r example, 0.0 3 kg-m^-d" 1 i s incorrect ; 3 0 g-m^-d" 1 i s correct . (Thi s rul e ca n b e broken i f th e rang e o f values being compared i s greater tha n 1 0 000 because th e comparison amon g values is easier i f the sam e prefix i s used throughout.) Table 2. Typical Ranges of Values for Plant Growth Parameters. Unit

Typical Value

Trend over Time

g-kg-'-d- 1 °

10 to 400

decrease

net assimilation rate or unit leaf rate

g-m^-d-1

1 to 30

decrease

leaf area ratio

m2-kg-1

10 to 60

decrease

specific leaf area

m^kg-1

5 to 30

decrease

leaf mass ratio (leaf weight ratio)

kg-kg'1

0.4 to 0.8

decrease

g-m^-d'1

1 to 40

rapid increase then gradual decrease

/Mnol-m^-s"1 c

1 to 40

decrease

Parameter relative growth rate or specific growth rate (RGR)

crop growth rate

single leaf photosynthetic rate (CO2 exchange) leaf area index

m

2

-2 leaf™ ground

0.01 to 10

large increase (sigmoid curve)

" Th e uni t g- g • d i s a commonly used unit for RGR, but it is not recommende d because the unit of grams is not a base uni t an d shoul d no t b e used i n th e denominator. Th e uni t ( d ) is also used fo r RGR be cause the gram s cancel ou t Thi s is confusing, however , because RGR represent s g new growth per g of existing biomass. Leaf weigh t ratio is th e commonl y use d ter m bu t k g is a unit o f mass , s o weight i s incorrect c

Us e moles for pur e substances , suc h a s (imo l o f CC^; us e kilograms or grams for mixed substances , such as grams o f biomass (ne t assimilation rat e o r cro p growth rate , g-m - d ) .

Table 3. Growt h analysis quantities derived from plan t mass and leaf area Symbol

Instantaneous Value

Absolute Growth Rate

AGR

dm/dt

Relative Growth Rate

XGR

\im - dm/dt

Leaf Area Ratio

LAR

Specific Leaf Area

Individual Plant

Derived Quantity

u!•

Formula for Mean Value over Time Interval (t rt,)

Dimensions

Units

m -t' 1

kg-d' 1

Qnm2-\n m,) I(t2 -/,)*= NAR -LAR

m-m"' -r'

kg-kg-'-d' 1

LA/m

[(LAI/m, ) + (L^/m^/2 =

A -m-'

m2-kg

SLA

LA/Ln

[(.Lu/L^ + duOL^W

A -m' 1

m2-kg

Leaf Mass Ratio

1MR

LJm

[(Z,n/m;) + (Z.^/m,)]/2

m -m'1

kg - k g1

Specific Leaf Mass

SIM

L./LA

\(Lml/LAI) + (L

m-A-'

kg • m' 2

Net Assimilation Rate

NAR

( 1 I LA ) - dm/dt

(nh - m,V(f, - 1,) • (In LA2 - In LA1)I(LA2 - L A1)

m-A-' -f

Percent Dry Mass

PDM

(mD/mF) • 10 0

Crop Growth Rate

CGR

1/GA • dm/dt

Leaf Area Index

LAI

LA/GA

(m2 -m,) I{t2-t1)" = Am/ At

SLA -LMR

M/La)V2

1

kg • m'2 • d' 1

[(mDI/mn) + (m D2/mr2)}/2

% = 0.01

(m2- m,)l(t 2 - 1,) • 1/GA = NAR • LAI

m-A-' T '

kg • m-2 • d' 1

(LAI+LM)/2-l/GA

A -A' 1

m2 • m- 2

LA = Leaf Area, L m - Lea f mass, G A = Ground Area , / = time, A = Area, m = mass = Weight, m DORf = Dry or Fresh mass. Not e tha t m = meter, but m = mass (became roman typ e is used for units but italic type i s used for physical quantities ; see Chapter 1) . a b

The most frequently used form of each equation i s boldfaced . In m 2 - In m, = In (m 2/m,).

Growth Analysis an d Yield Components 11

9

REFERENCES Causton, Davi d and Jil l Venus . 1981 . Th e Biometr y o f Plant Growth . Edwar d Arnold , London . Hunt, R . 1978 . Plan t Growt h Analysis . Edwar d Arnold , London . Hunt, R. 1982 . Plan t Growt h Curves : Th e Functional Approach t o Plant Growth Analysis . Univ . Park Press. Baltimore . Hunt, R. 1990 . Basi c Growth Analysis . Unwi n Hyman Ltd., London , UK ; and Winchester, MA. CONSULTANTS Ray Wheele r Charle NASA Kenned y Space Cente r Agricultur Florida Kentville Carl Rosen University of Minnesot a St. Paul, Minnesot a

s F. Forne y e Canada , Nova Scotia, Canad a

14 PLANT MOVEMENT S Wolfgang Haup t

Institut fii r Botani k un d Pharmazeutisch e Biologie der Universita t Erlangen-Nilrnber g Staudtstrasse 5 , D-91058 Erlangen GERMAN Y This chapte r deal s wit h terms use d i n th e stud y o f plant movements. A fe w terms are defined within other definitions ; these are also printed in boldfaced type. Word s in italics are themselve s define d elsewhere i n this chapter . 1. TYPES AND MECHANISMS OF MOVEMENT ciliary movements Bendin g of cilia or flagella of eukaryotic cells, caused by sliding of microtubula r doublet s alon g eac h other , usuall y resulting i n locomotion . Th e microtubules slid e because o f a tubulin-dynei n interaction. flagellar movements Rotatio n o f flagell a i n bacteria , drive n b y proton-motiv e force, resultin g in locomotion . running (running phase) Locomotio n o f peritrichous bacteria (having a uniform distribution o f flagell a ove r th e bod y surface; movement more o r les s straigh t forward), usually caused b y counterclockwise rotation o f flagella . tumbling (tumbling phase) Irregula r movement o f peritrichous bacteri a withou t locomotion, usuall y caused b y clockwise rotation o f flagella. Th e running phase i s interrupted b y a tumbling phas e eithe r autonomously in more o r les s regula r inter vals, o r a s a respons e t o a phobic stimulus. Usually , the directio n o f movement i s randomly different befor e and afte r a tumbling phase. cytoplasmic streaming Movemen t of cytoplasm (sometimes with nuclei) within the cell a s th e resul t o f actin-myosi n interaction; differen t type s are distinguishe d according to th e regularit y of velocity in time and space with which the cell organelle s are displaced. (Not e tha t th e ter m velocity comprises both speed an d direction! ) growth movement Irreversibl e curvatur e caused by differential growth ; i.e., plasti c extension o f cell walls, either differentiall y i n a single cell on opposite flanks, or, in a multicellula r organ , by differential cell growth on opposite flanks . Note: A growt h curvature can apparently be reversed , but i n fact thi s is caused by an opposite curvatur e located clos e t o th e firs t one .

120

Plant Movements 12

1

bending an d bulgin g Differentia l growth can caus e a curvatur e in eithe r o f two ways: (1 ) In an organ with a subapical growing zone, curvature is oriented awa y from the growth-stimulated flank (o r toward the growth-inhibited flank) : bendin g (some times also bowing). (2 ) In an organ with an apical growth center, shifting of maximal growth ou t o f the cente r result s i n outgrowth in that direction; hence , curvatur e is oriented towar d th e growth-stimulate d side : bulging . torsion Growt

h movemen t involvin g twisting of the organ .

turgor movement Reversibl e curvatur e caused by asymmetric change in length o r volume, eithe r in a single cel l b y asymmetric elastic extension/relaxatio n o f the cell wall upon uptak e or loss of water, or in a multicellular organ by differential swelling/ shrinking of cells o n opposite flanks. cohesion movemen t A chang e in cel l shap e resulting in curvature and caused by a los s o f water beyon d th e ful l relaxatio n o f the extende d elasti c wall. Becaus e of cohesion o f water in the vacuole, its adhesion t o the surrounding cytoplasm, and the firm attachment o f the latter t o the wall, this loss of water results in an elastic inward deformation o f the wal l (negative turgor) . Thi s slow movement can be followe d by a sudden return of the cell to its original volume and shape if the elastic deformation becomes stronge r tha n the cohesion, thu s allowing water-vapor bubbles to be formed in th e vacuole . A classica l example : annulu s cells o f the fer n sporangium . hygroscopic movemen t (als o swelling, shrinking ) Reversibl e curvatur e caused by water uptak e into/wate r loss ou t o f intermicellary spaces o f the cel l wall ; does no t need livin g structures onc e a suitable wal l texture ha s been developed . 2. CONTROL OF MOVEMENT: GENERAL autonomous (endogenous) Self-generate d movement, not depending on an external stimulus; the controllin g facto r is sometimes calle d internal stimulus. induced (exogenous ) A n externa l stimulus determine s tha t a movemen t (o r a change i n movement ) start s or ho w it i s executed. stimulus (signal, input signal) A physical or chemical factor that, when interacting with th e organis m o r cell , ca n elici t a movemen t o r modif y a n alread y existin g movement. It s quantity is characterized b y its intensity and its duration. I t can act in a scalar o r i n a vectorial way . A stimulus regulates the movemen t bu t doe s no t provide th e energ y for it . Thus , i f such a factor als o provides energ y for th e move ment, on e ca n debat e whethe r i t shoul d b e calle d a stimulu s (e.g. , photokinesis in cyanobacteria, desmids , etc.) . receptor A structur e o r substanc e i n cell s o r organisms , with which a stimulus interacts (stimulus perception). perception Interactio processes.

n betwee n stimulus and receptor tha t starts th e transduction

susception Sometime s th e ter m perception i s restricte d t o thos e processe s tha t involve livin g structures . I n thi s case , th e ver y first , pur e physica l effec t o f th e

122 Plant

Growth and Development

stimulus i s calle d susception; e.g. , displacemen t (sedimentation ) o f a statolith-lik e structure, or excitatio n o f a pigment molecule. Perception i n the stric t sense , then , would be the actio n o f the statolith o r th e excited pigment molecule on the respec tive sensitive cel l structur e (e.g. , a membrane). transduction (stimulus transduction, signal transduction, transduction chain) Biochemical o r biophysica l event s tha t follo w perception, finall y resultin g i n th e response; transductio n usuall y includes amplificatio n processes an d a tim e la g between perceptio n an d response. signal transmission Par t o f th e transduction processe s bridgin g the locatio n o f perception an d tha t o f respons e i f they do no t occu r a t th e sam e sites (structures , compartments, cells , organs) . latency (latency time) Tim e interva l betwee n star t o f stimulus and response . It s precise definitio n depend s o n th e respons e paramete r tha t i s measure d (e.g. , i n phototropism th e degre e of curvature measured unde r th e microscop e o r wit h th e naked eye ; a differential membran e potential). reciprocity (reciprocity law; in photoresponses: Bunsen-Roscoe law) Th e respons e depends quantitativel y neithe r o n th e intensit y o f th e stimulus alone, no r o n it s duration, but o n the produc t of both parameters. I f reciprocity holds, this is usually taken as indicating a lack of rate-limiting processes in the transduction chai n o r i n recovery processes o f the receptor. Accordingly , reciprocity is restricted t o a certain range of intensity and duration of the stimulus . (I t often doe s no t hol d for very low intensities o r very short durations. ) dose Tha t fractio n of the applied stimulus (product of intensity and duration) that reaches th e receptor. adaptation Relaxatio n o f response wit h persistent o r repetitiv e stimulation ; it is sometimes difficul t t o distinguis h whethe r th e stimulus change s th e receptor o r transduction syste m suc h tha t sensitivit y o r responsivit y i s reduce d (sensory o r response adaptation). tonic effect Chang e i n sensitivity or responsivit y to a stimulus caused b y external or internal conditions . 3. TERMS FOR INDUCED MOVEMENTS (TYPES OF RESPONSE) taxis (tactic orientation; formerly topotaxis) Movemen t of motile organisms, cells or organelles, th e prevailin g direction of which is determined by the directio n o f th e stimulus. Strictl y speaking, taxis is not alway s a single response, but ma y be a result of a series of responses (e.g. , chemotaxi s of bacteria). phobic response (formerly phobism or phobotaxis) Transien t chang e of movement of motil e organisms induce d b y a change in magnitude of a stimulus. Th e effectiv e change ca n b e a n increas e o r decreas e o f the magnitude ; that is , a step-up o r stepdown o f th e stimulus . Afte r th e previou s movement is resumed, its directio n may have changed, bu t wit h n o relatio n t o th e directio n of the stimulus . I n inhomoge-

Plant Movements 12

3

neous fields , repeated phobi c response s ca n result i n patterns o f distribution o f th e organisms; e.g. , accumulatio n i n a "light trap". kinesis Th e spee d o f movemen t o f motil e organism s o r cell s depends , unde r steady-state condition s o f inpu t an d output , o n th e magnitud e (an d sometime s probably als o direction) o f a stimulus. dinesis Applie s whe n th e spee d o f cytoplasmic streaming or th e fractio n o f cytoplasm involve d i n streamin g i s controlled b y a stimulus. tropism (tropistic movement) Curvatur e of organs or cells, the direction o f which is determined b y the directio n o f the stimulus. Tropism s ar e usuall y growth move ments; solar tracking, however, i s an example of a phototropism that in some plant s is caused b y turgor changes . nasty (nastic movement) Curvatur e o f organ s o r cells , th e directio n o f which is determined b y morphologica l o r physiologica l organization ; i t i s induce d b y a stimulus bu t independen t o f it s direction . Note : th e term s epinasty, hyponasty, nyctinasty, cyclonasty ar e use d t o describ e autonomous curvatures; thus , they do no t deal wit h true nasties . growth response Transien t chang e i n growt h rat e induce d b y a chang e i n magnitude o f a n externa l factor . Th e ter m i s sometimes als o use d t o denot e th e dependence of steady-state growt h rate on a stimulus. Mainl y used when light is the stimulus; then it is traditionally and inconsistently called light growth response rather than photo growth response. strophism Torsion

induce d by an externa l factor.

4. STIMULI. Note : stimul i ar e indicate d b y prefixes attache d t o -taxis , -nasty , -tropism, etc. : photo- (formerly: helio-) Induction polaro- Orientatio

by or orientatio n wit h respect t o light.

n wit h respect t o th e plan e of polarization o f radiation.

scoto- Induction b y darkness. Note: Strickl y speaking , darknes s canno t b e a stimulus but denote s th e absenc e of ligh t as a stimulus . gravi- (formerly: geo-) Orientatio n wit h respec t t o a n acceleration , especiall y gravity, but als o centrifugal acceleration . agravi- (formerly: ageo-) Indicate accelerational stimulus.

s tha t the orga n does no t respon d t o th e

thigmo- (formerly: hap to-) Induction by or orientation with respect t o mechanica l contact wit h a solid body . Note: Thigmotropism may be use d as a general term when a distinction cannot be mad e between tropistic an d nastic response i n tendrils. seismo- Induction by vibration (e.g., by wind action, shaking, usually also by sudden contact wit h a solid body or a fluid) . I t should not b e use d to replac e traumata-.

124 Plant

Growth an d Development

thermo- Induction temperature.

b y temperatur e o r orientatio n wit h respec t t o a gradien t i n

chemo- Induction by a specific substance o r orientation wit h respect to a gradien t of suc h a substance . hygro- (sometimes less correctly: hydro-) Induction or orientation with respect t o a gradient o f either.

b y fluid water or water vapor,

rheo- Induction

by or orientatio n wit h respect t o streamin g water or air .

aero- Induction

by or orientatio n with respect t o air , usually its oxygen content.

traumato- Induction

by or orientatio n wit h respect t o wounding.

electro-, galvano- Induction current. magneto- Induction

by or orientation wit h respect t o an electrical fiel d o r

by or orientatio n wit h respect t o a magnetic field.

avoidance response Movemen

t awa y fro m a nearby solid barrier .

step-up, step-down Denote s in which direction th e magnitude of the stimulus has to b e change d i n order t o induce a phobic response o r a growth response. 5. DIRECTION OR SENSE OF RESPONSE positive I n scalar stimulation : Wit h increase o f stimulus the spee d o f movemen t increases an d vic e vers a (sometime s als o "direct") . I n vectorial stimulation : th e movement ha s a prevailin g component towar d the sourc e o f a stimulus. negative I n scalar stimulation : Wit h increase o f stimulus the spee d o f movement decreases an d vice versa (sometime s als o "inverse") . I n vectorial stimulation: Th e movement ha s a prevailing component awa y fro m th e stimulu s source. ortho- Orientatio

n paralle l o r antiparalle l t o th e direction o f a vector stimulus.

plagio- Orientatio n a t som e determine d o r constan t angl e between 0 ° an d 180 ° to the stimulus source . dia- (not transversal) Orientatio n a t righ t angle to a stimulus source . Note: Fo r a ful l classificatio n o f a movement, one should combin e orientation , stimulus, and typ e of response; e.g. , positiv e phototaxis , plagio-gravitropism. one-instant mechanism (spatial sensing of direction) Th e direction o f stimulus is sensed a t on e instan t b y comparing the arrivin g stimulus at tw o (or more ) receptor sites. two-instant mechanism (temporal sensing of direction) Th e direction of a stimulus is sensed a t one receptor site only, comparing the arriving stimulus at two instants i n time; the arriving stimulus is modulated, e.g., by rotation of the cell or organism during locomotion . 6. TERMS FOR AUTONOMOUS MOVEMENTS. Note : Th e term s of this section containing nasty i n th e wor d ar e no t nastie s accordin g to th e definition ; however,

Plant Movements 12

5

they are occasionall y use d i n a purely descriptive way when the controlling facto r is not known . nutation Autonomous growth movement ove r extende d periods , i.e. , curvatur e of organs (o r chang e o f curvature) , cause d b y differential flan k growth , which is no t induced b y an externa l stimulus. (Th e ter m should not b e used to denote nastic or tropistic movements, which are induced movements. ) epinasty Growt h curvature in a morphologically downward sense, caused by faster growth rat e o f the uppe r sid e (e.g. , adaxial side o f leaves). hyponasty Growt h curvature in a morphologically upward sense, cause d by faster growth o f the lowe r sid e (e.g. , abaxial side of leaves) . nyctinasty A diurnal periodic upwar d and downward movement, usually of leave s or petioles , mainl y controlled b y the physiologica l cloc k but , in addition , synchro nized by an external factor. Sometime s not restricted to autonomous movements, but used als o fo r movement s tha t ar e induced b y rhythmic light-dark changes , o r onl y those that ar e induce d b y light-dark transition in the sens e o f scotonasty. circumnutation(formerly: cyclonasty) Periodi c change of growth curvature, the ti p of the orga n ideall y moving around a circle or cone; movemen t occurs as the regio n of highes t growt h rat e rotate s aroun d th e organ . Circumnutatio n i s no t alway s autonomous but ca n be the result of tropistic stimulation s with extended after-effects . autotropism A tendency of an organ to grow straight and to straighten a curvature induced b y a tropistic stimulus. CONSULTANTS Donat-Peter Hade r Andrea Universitat Erlangen-Nurnber g Universita Erlangen, German y Bonn Anders Johnsso n Hemmin University o f Trondheim Universit Dragvoll, Norwa y Goteborg Francesco Lend Masamits C.N.R., Istitut o d i Bioflsica Toky Pisa, Ital y Tokyo

s Siever s t Bonn , German y g I. Virgin y of Goteborg , Swede n u Wada o Metropolita n Universit y , Japa n

Hans Machemer Gottfrie Universitat o f Bochum Universita Bochum, German y Giessen

d Wagner t Giesse n , German y

Wilhelm Nultsch Manfre Universitat Marbur g Universita Marburg, German y Karlsruhe

d H. Weisensee l t Karlsruh e , German y

Peter Schopfe r Universitat Freibur g Freiburg, German y

15 GROWTH SUBSTANCES Robert E . Clelan d Department o f Botany University of Washington Box 355325 Seattle, WA 98195-532 5 U.S.A. Terms use d t o describe plant growth substances have been used in widely divergent ways. A s a result, there has been little attempt to standardize the definitions. Th e definitions presented here are based, as far as possible, on the most common usage at present. Som e terms, such as abscisic acid and ethylene, are not defined here, as they refer to a single compound . A few terms ar e define d within other definitions ; these ar e printe d i n boldfaced type. Word s in italics are themselve s define d elsewhere. antiauxin A compoun d tha t antagonize s th e biologica l actio n o f a n auxin, and whose inhibition kinetics are strictly competitive. Fo r example, p-chlorophenoxyisobutyric acid is an antiauxin because it shows competitive inhibitor kinetics, but 2,3 , 5-triiodobenzoic aci d (TIBA ) an d naphthylphthalami c aci d (NPA) , whic h ar e inhibitors of polar auxi n transport and show non-competitive inhibitor kinetics, ar e not antiauxins. auxin A compound that has a spectrum of biological activities similar to, but no t necessarily identical with those of indoleacetic acid. Thi s includes the ability to: (1 ) induce cell elongation in isolated coleoptile or stem sections, (2 ) induce cell division in callus tissues in the presence o f a cytokinin, (3) promote lateral root formation at the cu t surfac e o f stems , (4 ) induc e parthenocarpi c tomat o frui t growth , an d (5 ) induce ethylene formation. auxin antagonist A compound that antagonizes the biological action of an auxin. The inhibitio n kinetic s ca n be eithe r competitiv e o r non-competitive . TIB A an d NPA can be auxin antagonists, even though they are not antiauxins. bound auxin A molecule i n which an auxin i s bound to another compoun d (e.g., sugar, amin o acid , o r macromolecule ) vi a a covalen t bond . Sometime s calle d a conjugated auxin.

126

Growth Substances 12

7

cytokinin A compound tha t has a spectrum of biological activities similar to those of trans-zeatin . Thi s include s th e abilit y to : (1 ) induce cel l divisio n i n callus cell s in the presenc e of an auxin, (2) promote bud or root formation from callu s culture s when i n appropriat e molar ratio s t o auxin , (3) delay senescence of leaves , an d (4 ) promote expansio n o f dico t cotyledons . Th e ter m cytokini n is often restricte d t o compounds tha t contai n a n adenine ring structure; other compounds with cytokinin activity are calle d cytokinin-like. florigen A compound o r group of compounds, produced in leaves under inductive conditions, tha t i s transported i n th e phloe m t o buds and cause their developmen t to chang e fro m vegetativ e t o floral . T o b e considere d a florigen , a compound(s ) must b e effectiv e o n a wide range o f species, an d o n short-day , long-day, and day neutral plants . Fo r thi s reason , gibberellins ar e not considere d t o b e florigens. A s yet, the natur e o f florigen is unknown. gibberellin A compound containin g the ent-kaurene ring structure. I f it is active in a higher plant , it will have a spectrum of biological activities similar to thos e of gibberellic acid (GA 3). Thi s includes the abilit y to: (1 ) promote extension i n dwarf genotypes o f pea , corn , an d rice , (2 ) induc e d e nov o synthesis o f hig h p I form s o f a-amylase i n barley aleurone cells , and (3 ) induce or promote flowering in selected long-day plants when under short-day conditions. Gibberellin-Iike is used for all substances tha t hav e GA-lik e biologica l activity, but whose chemical structure has no t been defined . hormone-binding protein A protein that binds the hormone in a saturable, specific manner. (See phytohormone.) hormone receptor A hormone-binding protein that is shown to have a physiological effect afte r bindin g of the hormone . hormone sensitivity A n ill-defined , ambiguous term. I n general, it refer s t o th e amount o f respons e (i.e. , responsivity) t o a give n amoun t o f hormone . Th e sensitivity will depen d upon : (1 ) the concentratio n o f hormone fro m bot h endoge nous an d exogenou s source s tha t is present a t th e site of action, (2) the concentra tion of hormone receptors, (3) the affinit y o f the receptors fo r the hormone, and (4 ) the coupling of the hormone-receptor t o the final observed response. I t is not usefu l to tal k abou t hormon e sensitivit y o r a chang e i n sensitivit y unles s th e ter m i s carefully qualifie d as to th e typ e of sensitivity that is being considered . phytohormone (plant hormone) A compound, produced i n th e plant, that a t low concentrations ( 1 umol.L-1 or less) modulates o r regulates some aspects o f the bio chemistry o r physiolog y of cell s distan t fro m it s sit e o f synthesis . I n man y cases, hormones ma y als o influenc e th e cell s i n whic h they are produced . Example s of phytohormones are : auxins, gibberellins, cytokinins, abscisic acid , ethylene . plant growth regulator A compound that when applied at lo w concentrations ( 1 utmol-L-1 or less ) modifie s th e growth or development of the plant. A plant growth regulator ca n b e eithe r a n endogenou s compoun d (e.g . indoleaceti c acid ) o r a synthetic compound (e.g.a-naphthaleneacetic acid), but the term is primarily applied to synthetic compounds.

128 Plant

Growth and Development

polar transport Transpor t tha t i s dependen t o n metabolism , mor e rapi d tha n diffusion, an d predominantly unidirectional. Th e term has primarily been restricted to th e movemen t o f hormones , especiall y auxins. Transpor t throug h th e phloem , where a numbe r o f compound s ar e movin g unidirectionall y together , i s no t considered t o b e polar transport .

CONSULTANTS Robert Bandurski Michigan Stat e University East Lansing , Michigan

Richard P . Pharis University o f Calgary Calgary, Alberta, Canad a

Peter J. Davie s Cornell Universit y Ithaca, Ne w Yor k

Bernard O . Phinney University o f California Los Angeles, California

Michael L . Evan s Ohio Stat e Universit y Columbus, Ohi o

Frank B . Salisbury Utah Stat e Universit y Logan, Uta h

Richard D . Fir n University o f Yor k York, Unite d Kingdo m

Andreas Siever s University o f Bonn Bonn, German y

Arthur W . Galsto n Yale Universit y New Haven, Connecticu t

Lincoln Tai z University o f California Santa Cruz , Californi a

Russell L . Jones University o f California Berkeley, California

Kenneth Thimann The Quadrangle Haverford, Pennsylvania

A. Car l Leopold Cornell Universit y Ithaca, Ne w York

Anthony J. Trewava s University o f Edinburgh Edinburgh, Scotland

Hans Moh r Universitat Freibur g Freiburg, German y

16 BIOLOGICAL TIMING Willard L . Koukkari Department o f Plant Biology , University of Minnesota St. Paul, Minnesota 5510 8 U.S.A . Beatrice M . Sweeney 1 Department o f Biological Sciences , University of California Santa Barbara , Californi a 9310 6 U.S. A This chapter deal s with terms used in the study of biological timing. A few terms are defined withi n other definitions; these are also printed in boldfaced type. Word s in italics are themselve s define d elsewhere . acrophase La g o f th e maximu m (peak) o f a mathematica l curve (e.g. , cosine ) versus a reference ; th e phase angle o f the cres t o f the fitte d mode l in relatio n t o a reference tim e point . aliasing Misrepresentatio n o f a frequency to b e lowe r (o r perio d t o b e longer ) because intervals between consecutivel y spaced samples were too long . (Sometime s called folding effect.) amplitude Paramete r o f a rhythm , which fo r a mathematica l (e.g. , sinusoidal ) curve, is half the range from th e peak to the trough. I t is sometimes (e.g., by certain astronomers an d biologists ) use d for the entir e rang e from pea k to trough. annual Yearly

.

biological clock A biologica l variabl e showin g rhythmicit y (especiall y circadian rhythms) an d implyin g a mechanis m tha t impart s time information ; se e als o ref erences t o photoperiodis m i n Chapter 17. biological cycle Sequenc e o f events i n an organism that repeat i n the sam e orde r and at the sam e interval through time. [Whe n used in the context of the lif e history (life cycle ) o f an organism , the interva l through time may vary.] On e cycl e may be represented a s a circle (360°) .

1Deceased. 129

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biological rhythm A change i n a biological variabl e that recur s (repeats ) wit h a specifiable frequenc y an d pattern . Generall y viewed a s meeting th e criteri a o f an endogenous rhythm. chronogram Plo t o f a measure d variabl e o n th e ordinat e ( Y axis ) agains t th e measure o f time on the abscissa ( X axis) and used to illustrate the state of a variable over time . circadian pacemaker A postulated master ocillator that coordinates the period and phase o f circadian rhythms. circadian rhythm Biological rhythm havin g a perio d o f abou t 24 h (circa, about ; dies, day ) an d satisfyin g othe r criteria , suc h a s havin g a labil e phase tha t ca n b e shifted b y external environmental synchronizers an d continuin g for mor e tha n on e cycle (free-running) i n th e absenc e o f externa l environmenta l synchronizer s (e.g. , under LL o r DD). circadian time (CT ) Tim e tha t spans the circadia n period . Th e choice o f when a cycle start s i s arbitrary , especially unde r free-running conditions. Som e biologist s designate 0 0 h as the en d of the dark span (dawn) of an environmental LD cycle , or the phas e correspondin g t o thi s poin t i n constan t condition s (subjective dawn). Others selec t 0 0 h as the middl e of the dark span or the phase corresponding to this point i n constant conditions . circannual rhythm Biologica l (endogenous) rhyth m having a period of about (circa) a year . Sometime s use d whe n endogenieit y has no t bee n demonstrate d o r i s no t known. circaseptan rhythm Biologica (circa) seve n days.

l (endogenous) rhyth m havin g a perio d o f abou t

circatrigintan rhythm Biologica l (endogenous) rhyth m havin g a perio d o f abou t (circa) 30 days. (Sometime s called circalunar rhythm.) clock time Tim e provide d b y a cloc k o r watc h (nonbiologica l system) ; also se e biological clock and circadian time. cosinor analysis Dat a fitte d by cosine(s) of given period(s) (e.g., 2 4 h and 7 d) by a least-squares procedure an d used to estimate rhythm parameters (e.g. , acrophase(s), amplitude(s), an d MESOR). cosinor (polar) display Summar y of rhythm parameters (amplitude an d acrophase of each harmonic) estimated b y cosinor analysis an d displayed on pola r coordinate s so that th e phas e angl e of the maximu m (acrophase) o f each cosine curve included in the mode l is shown by the angular direction of a vector and the amplitude of each component i s represented b y the length of the vector. Th e 95% confidence limits of both for each harmonic are shown as an ellipse around the tip of the vector. Some times th e erro r ellipse is plotted to th e ri m for purposes o f comparing acrophases ; in suc h cases, th e lengt h of the vecto r i s not proportiona l to th e amplitude. damping A decreas e i n th e amplitude o f an oscillatio n (rhythm ) ove r time ; very common i n plant s as they mature and develop.

Biological Timing 13 dark break Interruptio DD Abbreviatio

1

n o f the ligh t spa n o r LL wit h a dark span (o r pulse).

n fo r continuous darkness .

desynehronization A chang e i n th e phas e relationshi p betwee n tw o o r mor e rhythms in an organism (internal) ; o r between th e rhythms of the organism and th e environmental cycle s (external) . Ther e ma y be desynchronization i n phase and/o r frequency. diel Th e 2 4 h day; 24 h period; rarely , if ever, use d when discussing plant rhythms but sometime s use d i n animal research . diurnal Ter m use d i n reference t o either a daily cycle or th e light spa n o f a 24 h day (e.g. , diurna l animal s compare d t o nocturna l animals) . Dependin g upo n th e context, ofte n bes t replaced b y other terms (e.g. , daily , circadian, light span, etc.) . endogenous rhythm A rhythm that persists (free-runs) under constant environmental condition s fo r mor e tha n on e complet e cycle . T o qualif y a s a biological rhythm, the oscillations must be shown to repeat wit h approximately the same period i n the absence of environmental cycle s o r synchronizers . entrainment Couplin g o f th e period o f on e rhyth m t o tha t o f anothe r cycl e o f about th e sam e length ; fo r example , the settin g o f a circadian rhythm to exactl y 24 h by an LD environmenta l cycle . Thi s usuall y involves both period and phase. free-running rhythm Se frequency Th

e endogenous rhythm.

e numbe r o f cycles in a unit tim e o r I/period .

frequency demultiplication Synchronizatio n t o a lon g period by a cycl e that i s a submultiple o f that period . (Th e convers e ma y also be observed, i n which case i t is referred t o a s frequency multiplication.) h Abbreviatio

n ofte n use d fo r hour(s) . (Se e Tabl e 5 , Chapter 1. )

harmonic Ter m use d t o describ e feature s of a periodi c curve . A nonsinusoida l periodic function can be mathematically expresse d as the sum of cosine curve s with period ta u ( ) , tau/2 , tau/3 , ...etc . Ta u i s called th e fundamental period, an d th e cosine wit h perio d ta u i s th e fundamental term or first harmonic. Cosine s wit h periods tau/2 , tau/3...etc . ar e calle d th e second, third, ... etc. harmonics. A curv e consisting onl y of a fundamental ter m i s purely sinusoidal with period tau . [Note : Tau i s sometimes use d a s an abbreviatio n fo r period.] high frequency oscillations Ultradian oscillations o f biologica l variable s havin g periods less tha n 3 0 minutes. Se e ultradian rhythms. hour-glass timer A mechanis m capabl e o f timing only a singl e tim e perio d an d likened t o a n hour-glas s (b y contrast t o a pendulum timer); thus , not a rhythm. infradian rhythm Biological rhythm having a period appreciably longer tha n 24 h; usually periods longe r tha n 2 8 h; therefore, a circannual rhythm i s infradian . LD Abbreviatio n for a light:dark cycle; for example, LD 15: 9 would indicate 24 h cycle(s) i n which a 1 5 h ligh t span alternates wit h a 9 h dark span.

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light break Interruptio

n o f the dar k span or DD with a light span (o r pulse) .

LL Abbreviatio n fo r continuou s light . Preferably , the energ y levels and spectra l characteristics should remai n constant . masking Alteratio n o f rhyth m parameter s o r characteristic s b y externa l (e.g. , environmental) conditions . Maskin g may be responsibl e fo r causing the amplitude of a circadian rhythm to increase , decrease , o r b e unexpressed ; o r i t ma y change a sinusoidal curve to a non sinusoida l on e o r visa versa. MESOR A n acrony m (midline estimating statistic of rhythm) use d i n cosinor analysis t o indicat e th e mea n of the mode l fitte d t o th e data. oscillator Se

e biological clock.

pendulum timer A n oscillating mechanis m capable of timing rhythms and likene d to th e pendulu m of a mechanical cloc k (b y contrast t o a n hour-glass timer). period Th e tim e require d t o complet e on e cycle . Biological rhythms ca n b e classified accordin g t o thei r free-runnin g period s (e.g. , ultradian, circadian, and infradian). phase Measur e o f timin g o f an y instantaneou s stat e withi n a cycl e (e.g. , peak , trough) o f a rhythmic variable versus a reference (either interna l or external) . phase angle difference Angula r difference between the phase of one cycle and that of another. phase response curve A graphic representation o f the extent of phase shifts cause d by treatments (perturbations ) o f short duration relative to one cycle and positione d at differen t part s o f th e cycl e (a pulse experiment). Phas e shift s ar e ofte n plotte d against the rhyth m stage (e.g . circadian time) when the treatmen t wa s administered. phase shift A change in th e phase o f one cycle relative to tha t o f the origina l o r previous cycle . Sometime s referred to as rephasing. I f the phase is advanced in time relative t o the reference cycle , the phase shift i s positive (+) an d involves the earlier occurrence o f events within a cycle; if the phase is delayed, the phase shift i s negative (-) an d involve s th e late r occurrenc e o f events within a cycle. photoperiod Lengt h o f the ligh t span in a 24 h LD cycle . Commonl y used in th e literature, althoug h light span (or photofraction) woul d b e preferabl e becaus e photoperiod ha s been used to refer to the light span (as defined here ) or to the whole daily cycle (comprisin g bot h th e ligh t an d dark spans). rhythm splitting Th e subdivisio n of rhythmic processes int o two or mor e groups with similar or different periods , sometimes observed in organisms under free-runnin g conditions. self-sustained oscillations Se

e endogenous rhythm.

semidian rhythm Biological rhythm wit h a perio d o f abou t 1 2 h . (Th e term , circasemidian, als o appear s in th e literatur e to indicat e a period o f 1 2 ± 2 hours.)

Biological Timing 13

3

sinusoidal rhythm A rhyth m that, when th e observe d measurement s ar e plotte d as a functio n of time, exhibit s a curve that approximate s a sine curve. skeleton photoperiod A synchronizing light:dark cycle with short ligh t spans marking the beginnin g an d th e en d o f the usua l light span o f a 24 h cycle. Fo r example , the skeleto n photoperiod o f a usua l L D 10:1 4 cycl e coul d includ e th e followin g sequence: 3 0 min ligh t span , 9 h dar k span, 30 min light span, and 1 4 h dark span . subjective day Unde r constan t condition s (e.g. , L L or DD) , i t i s the spa n corre sponding t o th e ligh t spa n o f a previously used 2 4 h LD environmenta l cycle . subjective night Unde r constan t condition s (e.g. , L L or DD), it is the span corre sponding t o th e dar k spa n o f a previously use d 2 4 h LD environmenta l cycle. synchronizer A n environmenta l signa l tha t ca n rephase (o r entrain) a rhythm . Also called th e Zeitgeber. Synchronizer ma y be preferred since it does not convey th e impression o f "givin g th e time " (a s Zeitgebe r does) , bu t merel y t o se t th e phas e and/or period of an endogenous rhythm. transient cycle Cycl e o f an abnorma l lengt h occurrin g immediatel y after a phase shift (o r stimulus) for synchronization t o a new cycle. Mor e tha n one transien t cycle may be observe d before th e usua l period i s reestablished . ultradian rhythm Biological rhythm havin g a perio d appreciabl y les s tha n 2 4 h (usually less than 20 h). Ultradia n oscillation s wit h periods les s than 30 minutes ar e called high frequency oscillations. Zeitgeber Se

e synchronizer.

CONSULTANTS Ruth Satte r (deceased ) Bernar University o f Connecticu t Universite Storrs, Connecticu t Besango Germaine Cornelisse n Guillaum e Fran University o f Minnesota Uta Minneapolis, Minnesot a Logan Ola M . Heide Theres Agricultural Universit y o f Norway Universit AS-NLH, Norwa y Bruxelles

d Millet d e Franche-Comt e n Cedex , Franc e k B . Salisbury h Stat e Universit y , Uta h e Vanden Driessch e e Libr e d e Bruxelle s , Belgium

17 DORMANCY, PHOTOPERIODISM, AND VERNALIZATION Frank B . Salisbury Department o f Plants, Soils , an d Biometeorolog y Utah Stat e Universit y Logan, U T 84322-482 0 U.S.A . This chapter deals with terms used in the study of vernalization, photoperiodism, an d dormancy. A few terms ar e defined within other definitions ; thes e ar e also printe d in boldfaced type. Word s in italics are themselves defined elsewhere althoug h italic s may also be use d fo r scientific names . abortion Arres t o f developmen t o f a structure . I n som e species , especiall y i n bulbous plants , the terms flower abscission and blasting are frequently used for flower abortion. Abscission is the abortion o f a structure that shrivels, dries up, and rapidly sheds; blastin g i s the abortion o f a structure tha t shrivels, dries up, but usuall y does not shed . I n certain studies , especially with roses, blindnes s i s used for early abortion o f the flower . absolute response Se e qualitative response. after-ripening Use d b y some author s with reference to an y change tha t goe s o n within a dormant see d o r bud during the breaking of dormancy. Othe r authors have used the term in a more restricted sense , limiting it to maturation changes that occur in th e embry o durin g storage. Th e firs t us e is preferable . allelopathic substances Organi c chemicals that are produced by one plant and that harm anothe r plant , sometimes by inhibiting germination. ambiphotoperiodic plants Plant s tha t respon d (e.g. , flower ) onl y whe n give n photoperiods tha t ar e shorte r tha n som e daylengt h o r longe r tha n som e longe r daylength (e.g. , shorte r tha n 1 4 h or longe r than 1 8 h); opposite t o intermediate-day plants. Thi s respons e i s rare, but i t was reported i n Madia elegans (Lewi s and Went , 1945) an d i n Setaria verticiltata (Matho n an d Stroun , 1960) . annual A plant wit h a life cycl e fro m see d t o see d tha t is completed i n only one growing season (o r on e year). anthesin Se e florigen , whic h Chailakhya n (1968 ) suggest s i s a combinatio n o f gibberellin an d anthesin . 134

Biological Timing 13

5

anthesis Th e tim e o f coming into ful l bloo m (e.g. , i n grasses, th e tim e when th e anthers ar e extende d fro m th e flowe r an d pollen i s released) . antiflorigen A

transmissibl e stimulu s that maintain s the vegetative state.

apical meristem (apex) A

meristem borne at th e ti p of a vegetative plan t stem .

autonomously-inductive plant (self-inductive) Flowerin g occurs more-or-less independently of day length (a s in day-neutral plants) and more-or-less independentl y of any othe r specia l environmenta l treatment . Tha t is , the respons e occur s unde r a variety of constant environmental conditions . axillary meristem Meristems i n the angle (axil) formed by the leaf petiole and th e stem; potentiall y capabl e of forming a branch. biennial A plan t tha t live s two growing seasons an d flowers and die s durin g the second season . Typically , biennial s gro w vegetatively during the firs t season , ar e induced t o flower by the lo w winter temperatur e experience d betwee n th e seasons , and flowe r an d di e th e secon d season ; tha t is , they hav e a n absolut e vernalization requirement. Ofte n thei r flowerin g i s als o promote d b y o r require s lon g days . (Many wild biennials ma y sometimes be to o smal l after th e firs t seaso n t o becom e vernalized, i n which case the y might live for mor e than two seasons, althoug h they flower only once before dying.) bolting Rapi d elongatio n o f a flowering stem fro m a vegetative rosette, often i n response t o vernalization o r lon g days. caulescent plant A to a rosette plant.

plant with leaves distributed along an elongated stem; opposite

critical daylength (critical day, critical photoperiod) I n plant s with an absolut e daylength requirement , th e daylengt h or photoperio d tha t mus t b e exceede d t o initiate long-day responses (e.g., flowering of long-day plants) or to inhibit short-day responses. (Som e author s hav e define d critica l daylengt h as th e daylengt h tha t produces th e smallest detectable response , or even 50% flowering, but those defini tions shoul d not be used.) critical nightlength I n plants with an absolute daylength requirement, the night length o r darkperio d tha t mus t b e exceede d t o initiat e short-da y responses (e.g. , flowering of short-da y plants o r formatio n of potato tubers ) o r t o inhibi t long-day responses. (Som e author s hav e defined critical nightlength as the nightlength that produces th e smalles t detectabl e response , o r eve n 50 % flowering , bu t thos e definitions shoul d no t b e used.) daylength (or day length) Sometime s (a s in these definitions) written as one word in th e sens e o f the photoperio d i n a natural 24-hour cycle of light and darkness , as this might influence plant growth or development. (Otherwise , in English the term is correctly written a s tw o words: da y length.) day-neutral plants (DNP ) Plant s that do not require a specific daylength treatment for flower initiation or othe r photoperiodicall y controlled response.

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determinate Wit h reference t o an organ such as a leaf, flower, or fruit tha t grows to a certain size and then stops growing; stems and roots, because the y are produce d by apical meristems, may continue t o gro w indefinitely, and are thu s indeterminate. developmental arrest A limitatio n o n see d developmen t tha t prevent s a viabl e embryo from germinatin g during growth of the seed. (Th e term could be applied t o other structures a s well.) devernalization Reversa l of the promotion of flowering induced by exposure to low temperatures (i.e. , by vernalization) b y an immediate exposure to hig h temperature s (e.g., 30 °C). I f a period o f time elapses a t neutral temperatures between vernalization an d th e high-temperatur e treatment , devernalizatio n usuall y fails. (I n som e perennial plants, Chrysanthemum, fo r example, prolonged exposure to low irradiance or shor t days also reverse s th e effect s o f vernalization. ) donor I n graftin g experiments , th e graf t partne r tha t i s assumed t o provid e th e stimulus (promotiv e o r inhibitory ) to th e receptor. dormancy Th e condition o f a seed or other plant organ when it fails to germinat e or gro w because i t ha s not bee n provide d with some special set of conditions (e.g. , a perio d o f lo w temperature , suitabl e wavelength s o f light , a treatmen t tha t wil l scarify th e seedcoa t o r leac h ou t inhibitors ) althoug h i t ha s bee n provide d wit h moisture, oxygen , and temperature conditions that are suitable for germination and growth after th e specia l requirements have been met. On e special condition can be sufficient tim e for the embry o to mature. Dormancy a s define d her e ha s bee n calle d endogenous o r innate dormancy or endodormancy (Lang et al., 1986) a s contrasted to imposed dormancy, which prevails if a n essentia l facto r (e.g. , H 2O o r O 2) i s lacking . Impose d dormanc y i s calle d quiescence here. Seed-coat-imposed dormancy and embryo dormancy have also bee n distinguished. Pomologists hav e use d rest i n th e sens e o f dormancy a s define d her e (Samish , 1954). Becaus e this use is rather specialized , it would be well to avoid the term rest. evocation Earl y responses o f receptor tissu e following environmental triggering or other form o f induction; usually related t o the flowering responses tha t occur at th e shoot ape x afte r arriva l of flower stimuli and prio r t o flower differentiation (floral initiation); defined by Evans (1969) to distinguish from induction, which occurs in the leaf. facultative response Se

e quantitative response.

florigen (floral stimulus) A postulate d flowering hormone or chemica l stimulus believed t o aris e i n th e leave s o f certai n plant s i n respons e t o a n appropriat e environmental treatmen t (suc h a s lon g o r shor t days ) and i s translocate d vi a th e phloem t o th e bu d apices wher e it causes evocation and flower initiation. Florige n may als o aris e autonomousl y i n th e leave s o f day-neutral plants o r b e transmitte d from a n induce d t o a noninduce d plant through a graf t union . fractional induction Induction cause d by one or more cycles of inducing conditions (e.g., shor t days ) interspersed wit h one or mor e cycle s of noninducin g conditions (e.g., long days).

Dormancy, Photoperiodism, an d Vernalization 13

7

germination Th e su m o f th e physica l and chemica l processe s within a see d tha t lead t o visible penetratio n o f the see d coa t b y the radicle (embryoni c root). grafting Th e process of combining two separate plants or plant parts (as two stems or a bud an d a stem) with the intention tha t they will unite and grow. Th e process may be carrie d ou t i n man y ways. Se e stock, scion, donor, receptor. hard seed Seed s that ar e kep t dorman t by hard, impermeable seed coats ; ca n be induced t o germinate by physical, chemical, or microbial abrasion/decomposition of the seed coat. impaction A treatment in which seeds are vigorously shaken to dislodge a cork-like filling (th e strophiolar plug) i n th e strophiolar cleft o f th e seedcoat , allowin g penetration o f water an d oxyge n and leading to germination. indeterminate Th e conditio n o f an apical meriste m of the shoot o r root that ha s the potentia l t o gro w indefinitely . Vegetativ e meristems are indeterminate . Con trasted to a determinate meristem, which produces a structure such as a leaf or flowe r and the n cease s to exis t as a meristem . induced state Conditio

n o f a plant that ha s been induced.

induction A phenomenon i n which some response (e.g., flowering) can be caused (induced) in an organis m by some treatment (e.g., an environmental condition such as cold or short days), and the response continues , or typically first appears, after th e treatment ha s been discontinued . Sometimes , inductio n appears to occu r autonomously i n th e absenc e o f an y obviou s treatmen t (i.e. , unde r a variet y of constan t environmental conditions) . Inductio n precedes evocation an d initiation. inhibitor Substanc e preventing germination, growth, flowering, or other responses ; that is , it need s t o be leached out , oxidized, or otherwis e metabolize d (e.g. , broken down or bound) to permit th e response. (Ca n also be applied externally to inhibit.) initiation, flower Th e beginnin g o f flora l differentiatio n (i.e., a morphologica l change) tha t follow s induction an d evocation. intermediate-day plant (IDP) A plant that fails to respond photoperiodically when days are eithe r to o shor t o r to o long; usually with referenc e to flower formation. juvenility Stat e o f a usuall y youn g plan t tha t i s incapabl e o f flowerin g unde r otherwise suitabl e conditions ; ofte n associate d wit h a variet y o f morphologica l features. (Se e ripeness-to-flower. ) Som e matur e wood y plants (i.e. , trees ) retai n juvenile feature s i n thei r lowe r parts , a phenomeno n sometime s calle d secondary juvenility. Terminatio n o f juvenility (achieving maturity) ma y differ fro m achieving ripeness-to-flower i n tha t plant s tha t reac h maturit y may flower (and/or lose thei r juvenile morphological features ) whether conditions change or not, whereas a plant that ha s reached ripeness-to - flower typically requires some special treatmen t (e.g. , long days, short days , low temperatures) t o actuall y flower. long-day plant (LDP) A plan t that flowers or otherwis e responds when th e day s are longer than some minimum length (depending on the species) and the nights are shorter tha n some maximu m length; opposite in response to short-day plant. Long day plants typically respond best t o continuou s light.

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long-short-day plant (LSDP) A plan t tha t require s a sequenc e o f long day s followed b y short day s for som e photoperiodi c response , usuall y flowering . maturity Th

e stag e reache d b y a plant when juvenility i s terminated.

meristem A tissue or group of tissues capable of cell division, enlargement (ofte n elongation), and differentiation t o produce determinate or indeterminate structures of the root/shoo t system . Apical o r axillary meristems of angiosperm s ma y becom e flowers. Vegetativ e meristem s ar e indeterminate, capable i n principl e o f growing indefinitely t o produc e stem s and roots . minimum leaf number Th e minimu m number o f leave s tha t mus t be produce d before flora l initiation occur s (in plants that produce the first flowe r a t the terminal bud) o r tha t mus t b e produce d befor e a plan t achieve s th e conditio n know n as ripeness-to-flower (o r ripeness-to-respond), i n which conditio n i t ca n become induced in response t o a photoperiodic o r other environmenta l treatment. monocarpic species Plant s tha t flowe r an d produc e seed onl y once an d the n die . They ma y be annuals, biennials, o r perennials. Contraste d wit h pofycarpic species. night interruption (night break or light break) Wit h reference t o inhibitio n o r promotion o f some photoperiodic respons e b y interrupting the dar k period wit h an interval o f light . Dependin g upo n species , th e ligh t brea k wil l b e mor e o r les s effective dependin g upo n whe n i t i s give n an d upo n th e irradianc e leve l an d th e spectral quality . Long-day plants typicall y requir e a muc h longe r perio d o f interruption at a higher irradiance leve l tha n do short-day plants. I f the ligh t brea k is effective , i t act s a s a long-da y treatmen t (promotin g a long-da y response o r inhibiting a short-day response). Respons e to a night interruption is an excellent test for a true photoperiodi c response . (Se e photoperiodism.) nightlength (night length) Sometime s written as one word in the special sens e of the dar k perio d i n a natura l 24-hou r cycl e o f ligh t an d darkness , a s thi s migh t influence plant growth or development. (Otherwise , in English the term is correctly written a s two words: nigh t length. ) null-response technique A n approach used in studies on photoperiodic phenome na and on other photobiological response s i n which irradiance levels of two opposing wavelengths (i.e. , red and far-red i n most applications) ar e balanced to produce th e same plan t respons e a s woul d b e produce d b y darknes s o r b y som e whit e ligh t source. perennials Plant s that live for an indeterminate number of growing seasons. Mos t perennials arepofycarpic an d flower once each year when they are sufficiently mature, but som e are monocarpic (flowe r onl y once afte r severa l years and then die) . phase change I n th e contex t o f juvenility, th e transition fro m th e juvenile to th e mature condition, permittin g sexual reproduction. photoperiodism Th e respons e o f organisms to th e relativ e length s of day and/or night. Mos t response s involv e changes in growth and development (e.g., flowering, tuber formation , and dormancy) . (Adjectiv e form i s photoperiodic.)

Dormancy, Photoperiodism, an d Vernalization 13

9

phytochrome Plan t pigment consisting of two interconvertible form s absorbing in the re d (c.a . 660-nm ) o r far-re d (c.a . 730-nm ) region s o f light . Phytochrom e i s directly involve d i n man y photomorphogeni c reaction s (e.g. , photoperiodism , dormancy breaking, deetiolation , chlorophyll formation, etc.). (Se e Chapte r 9. ) polycarpic species Plant s tha t flowe r fo r mor e tha n on e seaso n (ofte n man y seasons); al l polycarpi c species are perennials. Contraste d with monocarpic species. prechilling (stratification) Th e treatmen t i n whic h imbibe d (moist ) seed s o r dormant plant s ar e subjecte d t o col d temperature s (usuall y a fe w degrees abov e freezing an d preferabl y fluctuating ) fo r som e interva l o f tim e wit h th e goa l o f breaking dormancy an d promoting active growth; not t o b e confused wit h vernalization, which i s a promotion o f reproductive growt h by cold treatment . precocious Ter m applied to switching of developmental pathway s prior to natural maturity, a s in flowerin g induce d chemically or germination o f immature seed. qualitative response (absolute response, obligatory response) A plant response, usually flowering, that absolutely depends on some daylength, temperature, or othe r environmental stimulus . I f the plant does not experienc e the required stimulus , the response does not occur (e.g., the plant remains vegetative). Opposit e to quantitative response. quantitative response (facultative response) A plant response tha t is changed in number o r developmenta l rat e (e.g. , more flowers or tubers ) by a treatment suc h as a particular da y length o r an exposure to a period of low temperatures. Opposit e t o a qualitative or absolute response. I n the absence of the treatment, the response stil l occurs bu t a t a much slower rat e or fewe r organ s are produced. quiescence Applie d t o a viable, nondormant seed or bud that fails t o germinate or grow only because i t ha s not bee n provide d with suitable temperature, oxygen, and moisture conditions. Ha s also been called imposed dormancy or ecodormancy (Lang et al. , 1986) . Se e dormancy. recalcitrant seeds Seed s that have a very limited storage period that usually cannot be extended b y dry and cold conditions . The y are generally large and frequently ar e tropical species ; the y germinate at onc e afte r ripening . receptor I n graftin g experiments , th e graf t partne r that is assumed to receiv e th e stimulus (promotiv e o r inhibitory ) from th e donor. rejuvenation Reversio n (usuall y onl y partial ) o f matur e wood y plant s t o a secondary juvenile phase by such treatments as pruning, grafting, and treatment with gibberellins. rest Use d by pomologists (Samish , 1954) and others in the same sense as dormancy as defined here. Rest has als o been use d in the sens e o f quiescence as defined here . Hence, the ter m i s ambiguous and would best b e avoided. revernalization Effectiv

e chillin g treatment of plants that have been devernalized.

ripeness-to-flower (Bluhreife, ripeness-to-respond) A little understood condition of a plant that is reached a t a certain age when it is capable of becoming induced t o flower in respons e t o a photoperiodic o r othe r (e.g. , temperature ) treatment . Th e

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response unde r discussio n i s usually that o f flowering . Se e juvenility, maturity, an d phase change. rosette plant A plant with leaves comin g from a greatly shortened ste m at ground level; typica l o f man y biennial s durin g th e firs t yea r (e.g. , beets) ; opposit e t o a caulescent plant. scarification Breakin g o f th e seedcoa t barrie r b y mechanical treatmen t suc h a s abrasion b y san d o r grave l o r microbia l action ; allow s penetratio n o f wate r an d oxygen an d thu s allows germination . scion Th

e detached plan t par t tha t is grafted t o a stock.

short-day plant (SDP) A plant that flowers or otherwise respond s when the days are shorter than some maximu m length (dependin g on the species) and/o r when the nights are longe r tha n some minimum length; opposite t o long-day plant. short-long-day plant (SLDP) A plant tha t respond s photoperiodically (flowerin g is usually the response ) to a sequence o f short day s followed by long days. stock Th grafted.

e roo t o r roote d plan t t o whic h a detache d plan t par t (th e scion) i s

stratification Se

e prechilling.

summer dormancy Dormanc y of buds established during long days of summer or early autumn, usually in preparation fo r winter conditions. thermoperiodism Growth , development, or behavioral responses o f organisms to alternating da y and night temperatures. I n earlier researc h o n storage of bulbs, this term referred t o the requiremen t fo r different temperature s applied durin g different developmental stages . T o avoid confusion, this second usage should now be avoided. vernalin A substanc e postulate d t o aris e i n respons e t o vernalization an d t o promote reproductiv e growth . It s existence i s seriously doubted. vernalization Th e induction o f flowerin g i n a plant , mois t seed , o r developin g embryo o n th e mothe r plan t throug h exposur e t o lo w temperatures (usuall y a few degrees abov e freezing) . I n man y (perhap s most? ) cases , vernalizatio n lead s t o ripeness-to-flower, afte r which some other treatment is required to produce flowering. (For example , th e biennia l strain of Hyoscyamus niger ha s an absolut e requiremen t for lon g days following vernalization.) viable Applie d t o th e conditio n o f a seed tha t i s alive and capable of germination when provided with suitable environmenta l conditions; these conditions may include treatments t o brea k dormancy. winter annuals Plant s tha t germinat e i n lat e summe r or autumn , spending th e winter a s seedlings , an d flowerin g an d fruitin g durin g th e nex t growin g season . Flowering ma y be promote d b y exposure to th e lo w temperatures of winter.

Dormancy, Photoperiodism, and Vernalization 14

1

REFERENCES Chailakhyan, Mikhai l Kb . 1968 . Interna l factor s o f plan t flowering . Annua l Review s o f Plan t Physiology 19:1-36 . Evans, Lloy d T . 1969 . Th e natur e o f flower induction . In : L.T . Evans , editor . Th e Inductio n of Flowering, Th e Macmilla n Company o f Australia, Sout h Melbourne , p 457-480. Lang, Greg , Rebecca Darnell, Jack Early, and George Martin. 1986 . Repl y to letter. HortScienc e 21(2):186. Lewis, Harla n an d Frits W. Went. 1945 . Plan t growth under controlled conditions . IV . Respons e of Californi a annuals t o photoperio d an d temperature . Amer . J . Bot . 32:1-12. Mathon an d Stroun . 1960 . Thir d Internationa l Congres s o f Photobiology, Elsevier , Copenhagen . p 384-386. Samish, R.M . 1954 . Dormanc y i n woody plants . Ann . Rev . o f Plan t Physiol . 5:183-204 . CONSULTANTS These terms with preliminary definitions were published in the Flowering Newsletter, which was edited and issue d b y Abraham H . Halev y (no w b y Georges Bernier) . Th e followin g scientists responde d with comment s tha t strongl y influenced the fina l definitio n o f terms as presented here . Suresh C . Bhargav a Indian Agricultural Research Institut e New Delhi, Indi a

Moshe Negbi The Hebre w Universit y of Jerusale m Rehovot, Israe l

Georges Bernie r University o f Lieg e Liege, Belgiu m

E. H. Robert s University o f Readin g Reading, Englan d

Charles F . Clelan d U.S. Dept . of Agriculture Washington, D.C .

Kenneth C . Sanderso n Auburn University, Auburn, Alabam a

Abraham H . Halev y The Hebre w Universit y o f Jerusale m Rehovot, Israe l

Max Saure Diplom-Agraringenieur DorfstraBe 1 7 Moisburg, German y

Wolfgang Haup t Universitat Erlangen-Nurnber g Erlangen, German y Jean-Marie Kine t University o f Lieg e Li6ge, Belgium Rodney W . King CSIRO Black Mountain , Canberra , ACT , Australi a Donald T . Krize k USDA/ARS Beltsville, Marylan d Wim d e Mun k Bulb Research Cente r Lisse, Netherland s Klaus Napp-Zin n Botanisches Institut der Universita t Kol n (Cologne), German y

Walter W . Schwabe University o f Londo n Wye, England Atsushi Takimoto Kyoto University Kyoto, Japa n Kenneth Thimann University of California Santa Cruz , California Daphne Vince-Prue Goring-on-Thames Reading, Englan d Jan A . D. Zeevaar t Michigan Stat e University East Lansing , Michigan

18 STRESS PHYSIOLOGY Leslie H. Fuchigam i Department o f Horticulture Oregon State University Corvallis, Orego n 9733 1 Eugene V . Maas U.S. Salinit y Laboratory, USD A ARS Riverside, Californi a 9250 7 James M . Lyons Department o f Vegetable Crop s University of California, Davis Campus Davis, California 95616 D. William Rains Department o f Agronomy and Range Science University of California, Davis Campus Davis, California 95616 John K . Raison (deceased ) Plant Physisolog y Unit CSIRO Divisio n o f Food Researc h & School o f Biological Science s Macquarie University North Ryde, 2113, N.S.W . Australia Kenneth A . Shackel Department o f Pomology University of California , Davis Campus Davis, Californi a 95616-8683 The fiel d o f stress physiolog y is not onl y of considerable theoretica l importance ; i t is highly significant to agriculture. I n practice, researchers ten d to specialize within at leas t fou r subfields : chillin g injury, col d stress , water stress, an d salinit y stress. Yet, thes e subfield s hav e several basi c terms in common. Thus , this chapter begins with the term s commo n to stud y of all plan t stresses an d is then divide d into fou r sections representin g th e fou r subfields . Som e bold-fac e terms are als o define d in the contex t o f othe r definitions ; words i n italics ar e define d elsewher e o r ar e botanical names . Se e Chapter 6 for terms, units, and symbols used to describe plant water relations (e.g., water potential and osmotic, matric, and pressure potentials, etc.), 142

Stress Physiology 14

3

1. GENERAL STRESS-PHYSIOLOGY TERMS acclimation Adjustmen t of an organism to changes in external environments; thes e anatomical o r physiological change s ar e beneficial and increase the organism's resis tance o r tolerance to subsequen t environmenta l stress . adaptation Anatomica l o r physiologica l characteristic s o f a n organism , usuall y genetically fixed , tha t enabl e i t t o liv e in a given environment. avoidance A n acclimation or adaptation tha t reduces th e intensit y of stress at th e cellular level . calorie Th e unit of energy required t o raise the temperature of one gram of water by one degre e centigrade . Equa l t o 4.1842 joules (exactly) , the preferred SI unit. conditioning Exposur e t o temperature s slightl y abov e th e critical temperature chilling rang e fo r various period s o r other treatments tha t ca n limit the magnitude or affec t o r dela y th e onse t o f th e primary and/o r secondary events leadin g t o th e development o f visible symptoms. critical temperature Th e lowest ambien t temperature a t which the whole or part s of a living organism ca n endure fo r 30 min without injury. Th e critical (threshold) temperature ma y vary with the species, tissue , stage of growth, etc. Som e species ar e damaged b y cool temperature s abov e th e freezin g poin t (chilling-sensitive); other s only by subfreezing temperatures . (Critica l temperatur e i s not t o be confused with the chemica l definitio n o f critical temperature , whic h is the temperatur e o f vaporization o f a liquid. ) dehardening Synonymou s with deacclimation. The loss in plant tissues and organs of resistance to variou s stresses. hardening Conditioning or acclimation of an organism to a particular stress, which results i n increased resistance t o tha t stres s an d sometimes t o other stresses. Wit h relation to low-temperature stresses, hardening is a term used to describe physiological event s tha t lea d t o a lowerin g o f th e critical temperature fo r letha l injur y o f chilling-insensitive plant s expose d t o freezin g temperatures . Th e ter m hardening should not be used in relation t o chilling; the more appropriate ter m is conditioning. photo oxidation Oxidatio

n o f a substance cause d b y the absorptio n o f a photon .

primary event(s ) Th e primar y cellula r sensor(s ) o r trigger(s ) tha t initiate(s ) a series of secondary events leading eventuall y to th e visibl e symptoms of such strains as chitting injury. Th e primar y event(s) mus t occur a t th e critica l stress leve l (e.g. , critical temperature) fo r th e specie s o r tissue , mus t be rapid, and in th e shor t term , reversible. regrowth Th e ultimate viability test to determine survival following a stress. Plant s or cells are grow n or quiete d fo r a given period o f time following a stress and the n evaluated fo r eithe r roo t and shoo t regeneratio n o r increas e i n mass. repair Th e proces s b y which th e stress-induce d injur y o f a plan t i s partiall y or completely reverse d followin g remova l of the stress .

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secondary event(s ) Th e metaboli c an d cellula r change s followin g (directl y o r indirectly) as consequences o f the primary event and that lead to the visible symptoms of stress-induced injury . Th e secondary events are both time- and stress-dependent . In th e shor t ter m th e change s induce d ar e reversibl e i f th e stres s i s removed . However, i f the stres s is maintained, th e tissu e become s unabl e to recover . strain Th e observe d (deleterious ) biologica l change s tha t occu r i n respons e t o stress. (Th e term s stress and strain ca n be used in a manner analogous t o thei r us e in physics: stress is the forc e applied to an object, as a metal bar; strain is the actua l change i n shape o f th e object , a s bending of the bar. ) stress An y environmental condition tha t is capable of causing a biologically injurious chang e (strain). Sinc e plant s ar e autotrophs , an y chang e tha t directl y o r indirectly reduces plant growth (biomass accumulation) must be considered biolog ically injurious, even i f there ar e beneficial consequences fo r othe r aspect s of plan t function. Complet e description s o f a give n stress (o r strain ) shoul d includ e it s magnitude, duration, and rate of development. symptoms of injury Visibl e manifestation s of th e secondary events tha t reflec t injury t o th e cell s and tissue s cause d by chilling. tolerance Abilit y o f a n organis m o r it s cell s o r othe r part s t o surviv e the ful l impact o f a stress. Se e also avoidance. viability Th e stat e of living , growing, or developing . Th e viability test estimate s the relativ e o r absolut e surviva l o f a n organism. Fo r example , commo n cold hardiness viability tests includ e visual browning, conductivity, regrowth, vital stains such a s 2,3,5-tripheny l tetrazoliu m chloride, florescei n diacetate, Evan' s blue , an d neutral red . 2. CHILLING INJURY1 ameliorate T o provid e a treatment o r set of conditions tha t reduce the impac t of a chilling treatment b y alterin g th e tim e cours e o f sympto m development . Thus , amelioration i s confined to describin g changes in the tolerance of the plant tissu e t o the impose d chillin g stress. chilling Th e ac t o f exposin g plan t materia l t o a non-freezin g low temperature. This exposur e ma y or ma y not b e beneficial to th e plant . chilling injury A descriptiv e ter m fo r th e physiologica l injury t o man y plants , particularly those warm-season species (e.g. , crops) of tropical or sub-tropical origin, when the y ar e expose d t o low , but non-freezin g temperatures . chilling-insensitive Thos e plants that typically continue to grow and develop, albeit slowly, and ca n complete thei r lif e cycl e when continuously exposed to chilling tem peratures. Thes e plants ar e primaril y cool seaso n specie s o f temperate origin .

Original authors of this section were J.K. Raison an d J.M. Lyons.

Stress Physiology 14

5

r change s tha t correct th e advers e effect s o f th e secondary

chilling repair Cellula events.

chilling reversal Reversa l o f the primary event (s), which would be rapid and direct and shu t of f further stimulatio n o f the secondar y events. chilling-sensitive plants Thos e plants that are injured by exposure to temperatures below about 1 0 °C to 1 5 °C, but above freezing. (Th e warm-season crops of tropical or sub-tropica l origin s hav e receive d th e mos t study. ) Al l stage s o f growt h an d development o f the entire plan t (excep t perhap s the dry seed) ar e susceptible. Thi s susceptibility limit s th e seaso n o f growth, geographic distribution, an d postharves t storage conditions of these plants. (Harveste d plan t parts, especially fruit s o f some temperate plants , notably apples, pears, cranberries, asparagus, and potatoes, exhibit chilling damage durin g storage whe n exposed fo r extended periods a t temperature s very close to freezing , i.e., aroun d 2 ° C to 3 °C . However , thes e temperature s do not limi t growt h or geographi c distributio n o f thes e specie s a s exhibited b y warmseason crops.) chilling temperature An y temperatur e belo w th e critical temperature, bu t abov e freezing, tha t cause s injury . chilling tolerance Th e abilit y of chilling-sensitive plants o r plan t parts , t o endur e the metabolic dysfunctio n and/or harmful consequences tha t result from exposur e to chilling temperature s an d t o surviv e if th e abus e is not sustaine d beyond a certai n lethal point . Chillin g toleranc e i s use d t o describ e thi s differentia l respons e t o a chilling stress and should be confined to describing differences i n the time and course of th e developmen t o f chilling injury symptoms . chilling treatment Th e proces s o f exposur e t o a chilling temperature fo r a tim e period sufficient to caus e injury . conditioning Se

e definition i n Section 1 of this chapter .

critical temperature Se

e definition i n Section 1 of this chapter.

dysfunction A n impaire d functioning of plant tissues in response to chilling. Th e impairment i s reversible i f the tissu e i s returned t o a nonchilling temperature afte r a period of exposure. Howeve r thi s dysfunction become s irreversibl e after a longer period of time a t th e chillin g temperature. hardening Se

e definition i n Section 1 of this chapter.

intermittent warming Interruptio n of a chilling exposure with brief warm periods before th e critica l tim e is exceeded an d injur y occurs . Chilling-sensitiv e tissue can be kept fo r extende d period s a t chilling temperatures i f th e critica l tim e i s no t exceeded befor e intermittent warming and sufficient tim e is spent at the warmer temperature fo r th e tissu e t o recove r o r repai r prio r t o returnin g t o th e chillin g temperature. primary event(s) Se secondary event(s ) Se

e definition i n Sectio n 1 of this chapter. e definition i n Sectio n 1 of this chapter.

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sensitivity to chilling Th e ter m use d t o distinguis h relativ e sensitivit y (amon g chilling-sensitive plant species) o n th e basi s of their critical temperature an d critica l time t o develo p chilling injury. symptoms of injury Se

e definition in Sectio n 1 of this chapter .

3. COLD HARDINESS2 anaerobic stress A stress imposed on an organism as a result of the absence of the free oxyge n of air. Se e also ice encasement and flooding. bacteria nucleation inhibitors Chemical nucleation by ice-nucleation bacteria. calorie Se

s othe r tha n bactericide s tha t inhibi t ic e

e definition i n Section 1 of this chapter .

chilling requirement Low-temperatur e requiremen t t o overcom e dormanc y i n seeds and buds . (Se e dormanc y in Chapte r 17 ; also calle d endo-dormancy) cold hardiness Wit h referenc e t o th e exten t tha t plants ca n survive temperature s below freezing . Ca n b e quantitativel y expressed a s the critical temperature. cold injury Injur y incurred by biological materia l due to temperatures below 0 °C . The ter m i s often use d interchangeabl y with winter injury, freezing injury an d frost injury. cold protection Method s of guarding against injury from temperatures below 0 ° C. The ter m i s often use d interchangeabl y wit h frost protection and generally refers to protection o f blossoms i n th e spring . cold shock Impositio n o f a brief, non-freezing temperatur e resulting in a strain t o the organism ; ma y or ma y not induc e furthe r acclimation . convection Th e mass movement of heated liquid or gas. Whe n used in discussions of col d hardiness , th e ter m generall y refers t o mas s movement of heated air . critical temperature Se

e definition in Section 1 of this chapter.

deep supercooling Abilit y of organisms to supercool a t a temperature below that of intracellular freezin g of water t o a s low as the homogeneou s nucleatio n poin t o f pure water, approximately -40 °C. Thi s mechanism to avoid freezing exists in tissue such a s xylem ray parenchyma an d dorman t flower buds . Refe r to supercooling. degree growth stage model (°G S Model) Numerica l syste m fo r quantifyin g th e annual physiological growt h stages of buds of temperate plants . Th e annual cycle is divided int o 360-degree growth stages an d fiv e majo r poin t event s (0 °G S and 360 °GS = onse t sprin g growth ; 90 °G S = maturit y induction poin t whe n plan t firs t becomes responsiv e t o photoperiod ; 18 0 °GS = vegetativ e maturity and the onse t of dormancy (se e definitio n in Chapter 17) ; 270 °GS = maximu m rest ; 315 °GS end o f rest whe n chillin g requirement i s satisfied).

2

Original autho r o f thi s section was Leslie H . Fuchigam i

Stress Physiology 14 dehardening Se

7

e definition i n Section 1 of this chapter .

differential thermal analysis (DTA) Metho d o f determinin g th e exothermi c temperature differenc e between a reference an d a sample, usually biological, bein g frozen, o r th e differentia l endothermi c temperatur e o f a sample being thawed. electrical conductivity Th e curren t tha t will flow fro m on e fac e o f a uni t cub e of a given substance t o the opposite face when a unit potential difference is maintained between thes e faces. A technique use d t o determin e electrolyte leakage (membran e integrity) followin g a stress. electrical impedance Th e application of alternating electrical current to pre-frozen or froze n plant tissue s to predict damag e or measur e injury , respectively . electrolyte leakage A technique use d t o determin e cel l o r tissu e viabilit y by estimating membran e integrity . Followin g a stress, the tissu e i s shake n i n a give n quantity of water fo r a predetermined period , and the initia l electrical conductivity o f the effusat e i s determined. Th e tissue is then killed, either in liquid nitroge n or by heat, shaken fo r a given time, and the fina l conductivity determined. Viabilit y or th e extent of cellular o r tissue damage is estimated by the percentage loss of electrolytes . electrometric method (and cell freezing) Measurin g the electrolyt e leakag e fro m tissue caused b y membrane damag e from freezing . Variou s electrometri c method s are used ; refer s t o electrical conductivity, electrical impedance, conductivity, an d electrolyte leakage. endotherms Hea

t consume d durin g a thawing event.

evaporative cooling Coolin g cause d by the vaporizatio n of a liquid. I n th e even t of cold hardiness , i t would be the reductio n in temperature of biological matte r du e to th e loss of water t o th e atmosphere . exotherm Hea

t los t durin g a freezing event.

extracellular freezing Th

e crystallizatio n of apoplastic water.

extraorgan freezing Mechanis m o f freezin g tolerance i n plan t organ s b y wate r translocation fro m supercoole d tissue s o r organ s t o nucleatio n center s i n adjacent tissues (extratissue freezing) or outsid e the organ s (extraorgan freezing). flooding Se

e definitio n in Section 4 of this chapter.

freeze avoidance Lac k o f water crystallization i n tissues at subzer o temperature s caused by the absence o f either intrinsi c or extrinsic nucleators. Th e tissue supercools and thereb y escape s injur y cause d b y ice formation. freeze dehydration Los s o f symplastic water caused b y the vapor-pressur e defici t created b y ice in the extracellula r spaces. Th e degree of dehydration is a function of temperature; a s the temperature decreases , freeze-dehydratio n increase s resultin g in a concentratio n o f the cel l contents . freeze desiccation Se freeze tolerance Th apoplastic spaces .

e freez e dehydration. e ability of a cell or tissue to tolerate the presence of ice in th e

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freezing injury Injur

y o f biological materia l cause d b y sub-zero temperature .

freezing point Th e maximu m temperatur e attaine d b y th e releas e o f hea t (exotherm) followin g the initiatio n o f ice crystal formation. Th e temperature o f ice crystal initiation ma y vary, depending o n th e presence o f nucleating agents , but th e freezing-point temperatur e i s constant fo r an y given solution . freezing-point depression Th e lowerin g o f th e freezing-poin t temperatur e o f a solution b y the presenc e o f osmotically activ e compounds . frost A deposit of one o f several forms of ice crystals as a result o f sublimation of water vapor o n the eart h o r earth-borne object s colde r tha n 0 °C : Advection Frost: Occur s fro m th e movemen t o f larg e col d ai r masse s int o a n area fo r several day s resulting in severe low temperatures an d often accompanied by strong winds. Blackfrost: A dry freeze that occurs when the dewpoint is low, preventing watervapor crystallizatio n o n object s an d resultin g in the interna l freezing o f vegetation. Hoarfrost or White Frost: A deposit of interlocking ice crystals formed by direct sublimation o n objects . Radiation Frost: Occur s o n calm , clea r night s whe n ther e i s unimpede d radiation fro m th e earth resultin g in strong temperature inversions . Usuall y occurs in th e earl y mornin g hours an d i s characterize d b y relatively mild subfreezin g air temperatures. frost hardening Se e acclimation. Thi s proces s ma y be divided into thre e phases , based o n th e environmenta l stimulu s and the typ e of changes occurring . 1st Stage: Triggere d b y shor t days , whic h stimulat e th e productio n o f a translocatable hardiness-promoting factor, predominantl y an active metabolic process. 2nd Stage: Triggere d b y low temperature, often a mil d frost . Bot h metaboli c and physica l changes ar e involved . 3rd Stage: Foun d i n hardy woody species tha t have been expose d to prolonge d freezing temperatures , resultin g i n physical alterations . frost heaving Partia l o r complet e upliftin g o f a surfac e cause d b y ice expansion and resulting i n exposure an d injur y t o plants . frost plasmolysis Contractio n o f the dea d protoplast fro m th e cel l wall following a lethal stress. Primarily due to the inability of the cell to reabsorb and maintain turgor followin g a lethal stress. (See freeze dehydration.) frost protection Method s of guarding against injury from temperature below 0 ° C. Generally refer s to protectio n o f blossoms in th e spring. hardiness promoter(s) Naturall y occurring substance(s) synthesized in plants that induce(s) freezin g resistance. Se e also: translocatable hardiness promoter(s) . heterogenous ice nucleation Nucleatio n tha t i s catalyze d b y a soli d o r liqui d substrate tha t allow s groups of adsorbed water molecules t o assum e configurations that ar e able t o promot e furthe r condensation . Thes e nucleator s enhanc e th e probability that a cluster of water molecules of critical dimensions can form , which results i n crystallization.

Stress Physiology 14

9

hexagonal (H11) phase Th e H1l phas e is basically a liquid crystal in a hydrocarbon matrix penetrated b y hexagonally packed aqueou s channel s towar d which the pol e groups of the lipid are oriented. Lipid s in the H1l phas e provide a permeability barrier between interna l an d external environments. homeohydric plant (or homoiohydric) Se

e Section 4 of this chapter.

homogenous nucleation temperature Th e temperatur e a t which a water nucleu s forms tha t can be recognized by other water molecules as a structure resembling ice. Such cluster s o f molecule s aris e spontaneousl y b y rando m fluctuations . Th e probability tha t suc h a cluste r ca n serv e a s a n effectiv e nucleu s fo r crystallization depends o n it s siz e an d it s lifetime , which are a functio n o f temperature . Wate r spontaneously nucleate s a t -38. 1 °C . Th e approximat e homogenou s nucleatio n temperature, T n, fo r typica l plant solutions is given by the equation : A Tn = -( 2 A Tm + 38.1 °C) , where A Tm i s the melting point depression for the solution i n °C . ice deletion mutants Mutant s of ice-nucleating bacteria that do not ac t as ice nucleators. (Se e ic e nucleation active bacteria.)

ice encasement Th e partia l or complete coverin g of an organism by ice resulting in anaerobic stress. ice nucleation active bacteria (INA) Bacteri a capabl e of causing ice formation at sub-zero temperature s clos e to 0 °C . intercellular freezing Se

e extracellular freezing .

intrinsic ice nucleator Nucleator s o f ice formin g within plan t tissue s an d organ s resulting in crystallization a t relativel y warm subzer o temperatures.

inversion layer A meteorologica l phenomeno n i n whic h temperatur e rise s wit h increased elevation instea d o f falling (o r decreases les s than the adiabatic lapse rate would predict) . Ai r doe s no t ris e by convection throug h an inversion layer . killing temperature Th e temperatur e a t whic h an organis m cannot recove r fro m the stress as measured b y a viability test—often estimate d with the LT 50. LT50 Th e temperature a t which 50 % of the population survives an artificial temperature treatment . lamellar phase Orientatio n o f th e phospholipid s wit h thei r polar-hea d group s exposed t o a n aqueou s environmen t an d th e acy l sid e chai n oriente d towar d th e center o f the phospholipi d bilayer. low temperature exotherm (LTE) Exotherm o r exotherms tha t appea r a t a lower temperature tha n the large exotherm that represents freezin g o f extracellular water. The low temperature exotherms represent a small percentage of the total water. Lo w temperature exother m (LTE) pe r s e refers t o th e exotherm that occurs at approxi mately -37 ° C t o -4 0 °C, the nucleatin g temperature o f homogeneous water. low temperature injury Ambiguou s term used for injur y occurrin g from temper atures above freezing (chilling injury) t o temperatures as low as -196 °C . A better term migh t be freezing injury, th e temperatur e at which th e organis m no longer has tolerance.

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melting point depression Th e decrease in the temperature neede d t o melt a solid (e.g., ice) du e to th e additio n o f solutes . membrane fluidity A property of membranes determined by fatty-acid chain length, saturation level , an d sterol components . membrane permeability Th e degree t o which a membrane will allow a solvent o r solute to penetrate. minimum survival temperature Temperatur e abov e which cells eithe r tolerat e or avoid freezin g and belo w which they are killed . phase transition temperature Lipid s in membranes exist in one of several possibl e ordered structure s in which the individual lipid molecules have more or less motional freedom. I n a functional membrane, the lipids need to exist in a fluid state to allow rotational freedo m an d t o b e abl e t o diffus e i n th e plan e o f th e membrane . Th e temperature a t whic h th e lipid s adop t a hexagonall y parked structure , thu s losin g their diffusiona l freedoms , an d ente r a ge l phase i s known as the phas e transitio n temperature. photo oxidation Se e definition in Section 1 of this chapter . plasmolysis Th e withdrawal of water fro m a plant cel l causin g the protoplas t t o contract awa y from th e cel l wall (whic h may shrink elastically i f the cel l ha d bee n under turgor) . poikilohydric plant Se e definition i n Section 4 of this chapter . poikilotherm A n organism whose temperature varies with that of its environment. radiation frost Hea t radiate d fro m surfac e o f soil , trees , an d an y othe r soli d particles t o reduc e th e temperatur e lo w enough t o caus e fros t conditions . Soli d particles los e hea t mor e rapidl y tha n air , reducin g th e surfac e temperature . Eventually th e ai r at lo w levels become s coo l an d heav y compared t o ai r a t highe r elevations. Occur s mor e readil y o n cloudles s night s whe n ther e i s no barrie r fo r retaining th e hea t (i.e. , a barrier tha t radiate s th e heat back to earth) . regrowth Se e definition in Section 1 of this chapter . repair Se e definition i n Section 1 of this chapter . snow mold A diseas e o f cereal s cause d b y th e fungu s Calonectria graminicola. Characterized b y abundant white mycelium and found beneath prolonged snow cover. A similar disease cause d b y the genera Typhula, Sclerotium, or Fusarium, which are particularly prevalen t i n turf-grasses. sunscald A winter injury phenomenon i n which an otherwise hard y woody plant is partially thawe d o n its sunward side; when the sun disappears, the thawe d tissues experience rapi d intracellula r freezin g leading t o injur y an d death . supercooling Als o called undercooling or subcooling. Coolin g of a substance (i.e. , water) belo w th e temperatur e a t which a change of state (i.e. , liqui d to ice ) woul d ordinarily tak e plac e withou t suc h a chang e o f stat e occurring . Coolin g o f water below it s freezin g point withou t freezin g takin g place; thi s result s in a metastabl e state. (Se e als o homogenous nucleation temperature an d deep supercooling.)

Stress Physiology 15

1

T50 or TK50 Se e LT50. thawing Th e process of melting of ice formed within or surrounding the organism . Ice formed within the organis m ma y be extracellular or intracellula r in nature . theory of minimum artical cell volume Merryma n proposed tha t cells canno t re cover from a greater volume decreas e than 40 % to 50 % of the unfrozen volume . thermoavoidance A n organism that escapes high temperature (e.g., by transpiration and coolin g o f leaves, movemen t o f leaves in response t o hig h temperature). thermophile A n organis m that thrive s at hig h temperature. thermophilic Havin g th e abilit y to surviv e or eve n thriv e at temperature s abov e those considered t o b e lethal fo r most organisms. thermophily Th e tolerance o f certain organism s to temperature s between 3 0 ° C and 10 0 °C . thermostability Th e ability of proteins, enzymes, membranes, etc. to maintain their integrity with increasing temperature . thermotolerance Th e ability of an organism or its cells or other part s (tissues and organs) t o surviv e the ful l impac t of a temperature stress (i.e. , se e freeze tolerance). Tmax Temperatur Tmin Th

e a t whic h 100 % of the plant s are killed .

e minimu m temperature tha t results i n injury .

translocatable hardiness promoter(s) Sam e as hardiness promoter(s). Substance(s ) produced i n respons e t o a short photoperio d tha t i s perceived b y phytochrome in leaves an d translocate d i n the phloe m t o other plan t parts. viability Se

e definition i n Section 1 of this chapter .

visual browning A method o f determining injury t o plant tissues by observing th e presence o r absenc e of oxidative phenolic browning. winter chilling Temperature s adequat e fo r th e chilling requirement t o brea k dormancy. (Se e Chapte r 17. ) 4. WATER STRESS3 Despite the larg e body of knowledge concerning the role o f water in the physiology of plants, there is a lack of unanimity among plant physiologists regarding the nature and physiologica l basi s o f plan t response s t o water-limite d conditions . Fo r thi s reason, the definitions recommended below are mainly descriptive and not intende d to imply specific underlying physiological mechanisms for, or attribute adaptive value to, th e term s defined . Th e basi c approac h t o stress/strai n follow s tha t o f Levit t (1980). antitranspirant A to plants .

substance that reduces transpirational water loss when applied

Original autho r o f thi s section was Kenneth A. Shackel .

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bound water Th e quantit y of water i n a tissue tha t i s strongly held b y adsorptiv e (matric) force s an d i s difficult t o remov e b y tissue drying . Sinc e thi s quantit y will depend o n the drying conditions, th e utility of a distinction betwee n boun d an d free water i s questionable; hence , thi s term i s not recommended . cavitation Spontaneou s occurrence of a vapor phas e i n a liqui d unde r tension . Thought t o occu r i n the xyle m of plants under moderat e t o sever e water stress an d to resul t i n a reduce d capacit y of the xylem t o conduct water. critical period A perio d durin g crop developmen t i n which water stress will have a mor e profoun d effect o n harvestabl e yiel d than th e sam e stress a t othe r periods . Can be associated wit h stress-related reduction s i n early crop growth, which will be compounded ove r time , or, for crops grown for their reproductiv e structures , direc t stress-related effect s o n reproductiv e development . dehydration (desiccation) tolerance Abilit y t o continu e a plan t functio n (i.e. , reduce strain) despite reductions i n plant water potential ( ) . dehydration (desiccation) avoidance Abilit y to preven t reductions i n plant water potential ( ; i.e., reduce stress) despite reductions in environmental water availability. drought A condition i n which the availabilit y of soil water on a meso- o r macroenvironmental scal e i s generally insufficient t o suppl y the maxima l requirements of otherwise well-adapte d plants . drought avoidance Th e abilit y of a plant to survive or yield under drought conditions by increasing it s water suppl y (e.g., by deep rooting) relative to other plant s in the sam e environment . Doe s no t impl y desiccation avoidance. drought escape Completio n o f the entir e lif e cycle , o r critica l portion s thereof , during drought-free period s i n an otherwise drought-dominated environment . drought resistance Th e ability of a plant to survive or yield under drought conditions relative t o other plant s in the same environment. Drought tolerance, avoidance, and escape ar e type s of drought resistance . drought stres s Th e degre e t o whic h soil-wate r availabilit y fail s t o mee t th e maximal requirement s o f otherwis e well-adapted plant s ove r a meso - o r macro environmental scale . drought tolerance Th e abilit y of a plant to survive or yield under drought condi tions despit e th e lac k o f availabl e soi l wate r t o mee t it s maxima l needs. Plan t survival ma y be based o n reduction s i n water need (e.g. , stomata l closure) ; hence , drought toleranc e does no t impl y desiccation tolerance. evaporative demand Th e capacit y o f th e aeria l environmen t t o caus e wate r evaporation fro m a give n object , usuall y a plan t o r plan t canopy . Evaporativ e demand i s influence d b y man y environmenta l factor s includin g radiatio n load , temperature, vapor pressure deficit (VPD), an d win d spee d i n additio n t o plan t o r plant-canopy characteristics . flooding Th e partia l o r complet e covering of a n organis m b y water resulting in anaerobic stress.

Stress Physiology 15 hardening Se

3

e definition i n Section 1 of this chapter .

homoiohydric Plant s tha t maintai n a relativel y constan t leve l o f hydratio n compared wit h large changes tha t occu r i n the water potential o f their environmen t (e.g., vascula r plants) . hydrophyte A plan t adapte d t o environmenta l condition s o f partia l o r ful l submersion i n fre e water . mesophyte A availability.

plan t adapte d t o environmenta l condition s o f moderat e wate r

osmoregulation (osmotic adjustment) Partia l o r complet e maintenanc e o f cel l turgor ove r a rang e o f tota l water potential s b y regulated change s i n cel l osmoti c potential. Thi s process i s well documented i n the turgo r an d volume maintenanc e of certai n alga l specie s when expose d t o change s i n th e osmoti c potentia l o f thei r aqueous environment . Th e adaptiv e importanc e o f thi s process i n vascula r land plants i s controversial . paraheliotropic Orientin g parallel t o the incident solar radiation. Paraheliotropi c leaf movement s i n plant s unde r water stress reduce s intercepte d radiatio n an d ca n reduce leaf temperatur e an d leaf transpiration . phraeatophyte A plan t wit h the abilit y to thriv e in a dry environment, i n which high evaporativ e demand s ar e me t b y havin g root s dee p enoug h t o reac h a permanent wate r tabl e (se e drought avoidance). poikilohydric Plant s that equilibrate with the water potential of their environment and, for lan d plants, ar e capabl e o f assuming a wide range of hydration states. Relative Water Content (RWC) Th e wate r conten t o f a tissu e expresse d a s a percent of the wate r content o f the sam e tissue at ful l hydratio n (= 0). SPAC Th e concept o f transpirational water flow through aSoil-Plant-Atmosphere Continuum, usuall y i n term s o f a n Ohms-La w analog y with A T a s th e potentia l gradient, transpiratio n a s th e flux , an d th e hydrauli c resistance betwee n an y two points o f the pathwa y as the rati o gradient/flux. succulents Plant s havin g thick leave s with a high tissue-water content. Typicall y xerophytes tha t hav e a thic k cuticle, lo w transpiration rates , an d th e hig h water use efficiency (WUE) associated wit h CAM metabolism . vapor pressure deficit (VPD) Th e difference between the actua l vapor pressure of water i n th e ai r an d it s saturate d (i.e. , 10 0 % relativ e humidity ) vapo r pressure , expressed i n pascals : Pa . I t i s als o logica l t o us e th e ter m vapor density deficit although thi s i s seldo m done . (Vapor density is expressed i n gram s of wate r pe r cubic meter o f air). water deficit An y value of tissue tha t is below the highest value exhibited by that tissue i n it s mos t hydrated natural state. Doe s no t impl y water stress. water stres s Ca n refe r t o a n environmenta l condition of either exces s or lac k of water, but th e ter m i s usually used t o indicat e a lack of water. Wate r stres s a s a n environmental conditio n (sometime s referre d t o a s drought stress) shoul d b e

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expressed a s th e amoun t o f water availabl e to a plant compare d wit h it s maximal requirements. Wate r stress as a physiological conditio n ma y be expressed as plantwater potential ( ) , but the association betwee n an d water-stress-related injur y is controversial. Se e stress i n Section 1 of this chapter . water status Th e genera l conditio n o f a plant relative to any limitations impose d by a lac k of water . water use efficiency (WUE) A comparative measure of plant productivity per unit water used, in which the appropriate units for productivity and water use will depend on the objectiv e o f the comparison . Agricultura l WUE can be defined for a growing season either as yield per unit irrigation water applied or biomass produced pe r unit of transpiration, wherea s instantaneou s physiological WUE can be defined as moles of carbon dioxid e fixe d b y photosynthesis pe r mol e of water transpired . xeromorphy Morphologica l characteristics , suc h as small , tough leaves , a heavy cuticle, etc. , that ar e generally important for adaptation to dry environmental conditions. xerophiiy Th e combined adaptiv e morphological and physiological characteristic s of plant s able to gro w under dr y environmental conditions. xerophyte A availability.

plant adapted to environmental conditions of severely restricted water

5. SALINITY STRESS4 acclimation Se

e definition in Section 1 of this chapter .

biosalinity Interpla

y of saline habitat s and th e organism s living within them.

cation exchange capacity (CEC) Th e total quantity of cations that a soil or othe r material can adsorb a t a specific pH, usuall y expressed a s centimoles (millimole s is preferred SI ) of a specifi c cation pe r kilogra m of exchanger. chloride salinity Salinity

i n which chlorid e is the dominan t anion.

clay dispersion Th e separatio n o f cla y int o individua l component particle s re sulting from th e presence of monovalent cations. I n saline soils, sodium is frequently responsible for th e dispersio n o f clay. Soil s with dispersed cla y are dens e and hav e a greatl y reduced permeability . compatible solute A n organic solute that accumulates inside cells without causing severe metabolic disruption and may aid osmoregulation; for example, glycine-betaine, proline, glycerol. cyclic salt Sal t derive d fro m th e se a or salt lakes that is deposited o n plant s and soils fro m win d or rainfall.

Original authors for thi s section were D.W. Rains and E.V . Maa s who wish to express special thanks t o Richar d H . Niema n for hi s thorough review of and suggestion s for thi s set o f definitions .

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dehydration Los s of water fro m plan t tissue s i n excess of water uptake . desalination Th e removal of salt from soil or water by physical or chemical means . electrical conductivity (EC) A measur e o f th e abilit y of a solutio n t o conduc t electrical current ; i t is correlated wit h the concentration o f the ions in the solution . EC i s used t o expres s th e concentratio n o f salt in saline soil solutions and i s given as decisiemens pe r mete r (dS/m ; millisiemens pe r mete r i s preferred SI) . euhalophyte (true halophyte) A plant whose growth is maximum a t a soil wate r salinity of about 1 0 g total dissolve d solids pe r lite r ( S 0. 8 MPa; EC 2 0 dS/m) and decreases at eithe r highe r o r lowe r salinities . exchangeable sodium percentage (ESP) Th e percentage o f the total exchangeabl e cations tha t i s sodium. Soil s wit h high ESP ca n be difficult soil s t o reclaim . flocculation Th e clumpin g o f cla y particle s int o aggregate s a s a resul t o f th e neutralization o f charged surface s of the clay . glycophyte A plant tha t grows optimally in nonsaline habitats . halomorphic soil A suborder o f the intrazonal soil order, consisting of saline and sodic soils forme d unde r imperfect drainage in arid regions and including the grea t soil group s Solonchak or Salin e soils , Solonetz soils, and Soloth soils . halophyte A plan t tha t grow s and complete s it s lif e cycl e in saline habitats . hardening Se e definition in Section 1 of this chapter . ionic effect A toxi c or nutritiona l effec t o f specific ions on a plant. leaching requirement (LR) Th e amoun t o f water i n exces s o f the plan t require ment tha t i s neede d t o remov e sal t fro m th e roo t zon e i n orde r t o preven t soi l salinity fro m exceedin g a specified value. mangroves Grou p o f woody plants (about 1 1 genera) tha t grows in saline aquati c habitats (e.g. , marine estuarie s an d swamps ) and is capable o f tolerating sea water. Common gener a includ e Avicennia and Rhizophora. mesophyte A plant adapte d t o a moderately moist habitat. miohalophyte A plant that exhibits maximum growth in nonsaline soils but steadily decreasing growth with increasin g salinity; such plants tolerate highe r salinit y than gtycophytes. oligohalophyte A plant adapte d t o habitat s of low salinity ( s 0.0 4 t o 0. 4 MPa at fiel d capacity ; EC 1 to 1 0 dS/m). osmoregulation Change s i n cell osmotic potential tha t tend to maintai n turgor . osmotic adjustment Change s in concentration o f certain cell solutes (se e compatible solute) in response to changes in cell water potential. Thes e changes contribut e to osmoregulation. (Se e als o osmoregulation i n Section 4 of this chapter.) osmotic effector Se e osmoticum. osmotic shock Osmotic stress cause d b y a sudde n and drasti c change in externa l osmotic potential.

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osmotic stres s Externa l osmoti c potentia l below or abov e cel l osmoti c potential sufficient t o cause strain (e.g., reduced yield). Osmoti c stress almost always refers to external osmoti c potentials belo w those in the tissues, but osmotic potentials abov e those o f th e tissu e (i.e. , les s negative ) ma y have som e deleteriou s effect s suc h a s causing certain fruit s (e.g. , cherries ) t o split. osmoticum A solut e tha t decrease s osmoti c potential s o f cel l solution s a s it s concentration increase s (i.e. , any solute). physiological drought Plan t water deficit (i.e. , low tissue water potential) cause d by salinity, lo w soil wate r potential, o r othe r stress factors. polyol A

compound containin g many alcoho l groups.

reclamation Wit h reference to saline soils, the process of removing excess sal t t o a leve l tha t permit s production o f plants without significant advers e effects . saline adaptation Geneti c modification of individuals in a population that increases their abilit y to surviv e excess salt. saline adjustment Physiologica l and biochemical changes of individual plants that increase thei r ability to surviv e excess salt . saline-sodic soil A

soil tha t i s both saline an d sodic.

saline soil A soi l tha t ha s a n electrica l conductivit y in a saturated-paste extrac t greater tha n 4 dS/m. Th e solubl e salt conten t o f such soils is sufficient t o interfer e with the growth of many plant species. Sensitiv e crop plants are affected a t half this salinity and highl y tolerant one s a t abou t twice this salinity. saline stress Externa l salt concentrations sufficiently high to reduce plant growth. Injury ma y resul t fro m osmotic stress, io n toxicitie s (se e ionic effect), and/o r nutritional imbalance . salinity Presenc e of inorganic ions in solution. Th e term often i s used to refer t o ion levels hig h enough t o cause osmotic stress. Th e predominant ions include Na +, Ca2+, Mg 2+, Cl- , SO42-, and HCO 3'. Thes e ions may have specific io n effects a s well as osmoti c effects . Boro n an d othe r toxi c substances ma y be presen t bu t d o no t contribute significantl y to salinity. salination Th

e proces s o f accumulation of soluble salts in the soil .

salinity threshold Th e maximum salinity a plant can tolerate without a reductio n in growth below tha t which occurs unde r simila r but nonsalin e conditions . salt-affected soil A soil containing excessive concentrations of soluble salts and/or exchangeable sodium. salt balance A steady-state concentration o f salt determined by a balance between the influ x o f salt an d th e efflu x o f salt fro m th e system . Thi s balanc e i s frequently disturbed b y inappropriate managemen t o f water and/o r soil s o r a chang e i n th e climatic conditions . salt glands Specialize d cells or group s of cells on o r nea r the surfac e o f leaves or stems tha t secrete salt an d hel p control levels of salt in plant cells.

Stress Physiology 15

7

salt resistance Th e abilit y o f plant s t o tak e som e actio n o r emplo y som e mechanism t o avoi d detrimenta l effect s o f salinity. Th e mechanis m o f resistanc e should b e specifie d i f it i s known. salt tolerance Th e abilit y of plants to cope with salinity. saturated soil paste A particular mixture of soil and water. A t saturation, the soi l paste glisten s as it reflect s light , flows slightly when the container i s tipped, an d th e paste slide s freel y an d cleanl y from a spatula . saturation extract Th tent.

e solution extracte d from a soil a t its saturation water con -

saturation percentage Th e water content of a saturated soil paste, expressed o n a dry-mass percentage basis . sodic soil A soil that has an exchangeable sodium percentage (ESP) greate r tha n 15. The exchangeabl e sodiu m of such soils often adversely affects soi l structure and may be deleterious t o plan t growth. sodicity Presenc

e of excess sodiu m in soils wit h a pH rang e of 8.5 to 10.0 .

sodium adsorption ratio (SAR) A relatio n betwee n solubl e sodiu m and solubl e divalent cation s tha t ca n be use d t o predic t exchangeable sodium percentage of soi l equilibrated wit h a give n solution. I t i s defined as follows:

where concentration s ar e expresse d i n millimoles per liter . succulence 1 . A morphological conditio n denoting thick, fleshy plant organs with a hig h water content. 2 . Juiciness ; measure d as the water content pe r uni t surface area o f plant tissue . (Se e definitio n i n Section 4 of this chapter. ) sulfate salinity Salinity xerophyte Se

i n which sulfate is the majo r anion.

e definitio n in Sectio n 4 of this chapter. REFERENCES

[Anonymous]. 1984 . Glossar y o f soil science terms. Soi l Sci. Soc. Amer., 67 7 South Segoe Road , Madison, Wisconsin , p 38. Burke, M.J. , L.V . Gusta , H.A , Quamm e an d C.J . Weiser . 1976 . Freezin g an d injur y i n plants. Annual Review o f Plant Physiology 27:507-528 . Chapman, V.J . 1960 . Sal t Marshe s an d Sal t Desert s o f th e World . Interscienc e Pub., Inc . New York, p 392 . Franks, F. 1981 . Biophysic s and biochemistry of low temperatures and freezing. In : G.J. Morri s an d A. Clark , editors . Effect s o f Lo w Temperature s o n Biologica l Membranes . Academi c Press , London, p 3-19 . Levitt, J . 1980 . Response s o f plant s t o environmenta l stresses. Vo l 1 , Chilling , freezin g an d temperature stresses . Academi c Press, Ne w York.

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Levitt, J. 1980 . Response s of plants t o environmenta l stresses, Vol 2, Water, radiation , salt, and other stresses. Academi c Press , Ne w York. Li, P.H. an d A Sakai , editors. 1978 . Plan t Cold Hardiness and Freezing Stress . Vo l 1. Academi c Press, Ne w York. Li, P.H . an d A Saka i 1982 . Plan t Cold Hardines s and Freezin g Stress. Vo l 2. Academi c Press , New York. Little, R.J . an d C.E . Jones . 1980 . A dictionary of botany. Va n Nostran d Reinhold, Ne w York. Luyet, B.J . 1968 . Th e formatio n o f ic e an d th e physica l behavior o f th e ic e phas e i n aqueou s solutions and i n biological systems. In : J. Hawthorne and E.J. Rolfe , editors. Lo w Temperatur e Biology of Foodstuffs. Pergamo n Press , Ne w York, p 53-77 . Lyons, J.M. an d R.W . Breidenbach . 1987 . Chillin g injury . In : J . Weichman , editor. Postharves t Physiology of Vegetables. Marce l Dekker, Inc. , New York, p 305-326. Mazur, P. 1969 . Freezin g injur y i n plants. Annua l Review of Plant Physiology 20:419-448. Raison, J.K. an d J.M. Lyons . 1986 . Chillin g injury: a plea for uniform terminology . Plant , Cell, and Env. 9:685. Sakai, A. and W. Larcher. 1978 . Fros t survival of plant responses and adaptation to freezing stress. Springer-Verlag, Ne w York. Salisbury, F.B. , an d C.W. Ross. 1992 . Plan t Physiology , Fourth edition. Wadswort h Publishin g Co. , Belmont, California. Saltveit, M.E. , Jr . an d L.L . Morris . 1990 . Overvie w on chillin g injur y o f horticultura l crops. In : C.Y. Wang, editor. Chillin g Injury o f Horticultural Crops. CR C Press, Inc., Boca Raton, Florida . p 3-15 . Sinclair, T.R . an d M.M . Ludlow . 1985 . Wh o taugh t plant s thermodynamics ? Th e unfulfille d potential o f plant water potential . Aust . J . Plan t Physiol. 12:213-217. Staples, R.C. an d G.H. Toenniessen , editors . 1984 . Salinit y Tolerance i n Plants - Stategies for Crop Improvement. Joh n Wile y & Sons, New York. Turner, N.C . 1979 . Drough t resistanc e an d adaptatio n to water stres s i n crop plants . In : Stres s physiology i n cro p plants . H.W . Mussel l and R.C . Staples , editors . Wile y (Interscience), Ne w York. United States Salinity Laboratory Staff . 1954 . Diagnosi s and Improvement of Saline and Alkali Soils. U. S. Dept. Agr. Handboo k No . 60. p 160 . Weiser, C.J . 1970 . Col d resistanc e an d injur y i n woody plants. Science . 69:1269-1278 . Weiser, C.J . 1982 . Plan t Cold Hardines s and Freezing Stress. Vo l 2. Academi c Press, New York. Consultants John S . Boyer Ton University o f Delaware Orego Lewes, Delawar e Corvallis

y H.H. Che n n Stat e University , Oregon

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l Epstein (retired ) y of Californi a , Californi a

William J. Bramlag e Lelan University of Massachusetts USD Amherst, Massachusett s Riverside

d E. Francoi s A Agricultural Research Servic e , Californi a

R. Willia m Breidenbac h Catherin University of Californi a USD Davis, Californi a Riverside

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Michael J. Burk e Laurenc Oregon Stat e Universit y Universit Corvallis, Orego n Saskatoon

e V. Gusta y o f Saskatchewan , Saskatchewan, Canada

Stress Physiology 15 Anthony E . Hal l University o f California Riverside, Californi a Robert L. Jefferie s University o f Toronto Toronto, Ontario , Canad a

Mikal E . Saltvei t University of California Davis, California

Delmer O . Ketchi e Washington State Universit y Wenatchee, Washingto n

Richard C . Staple s Cornell Universit y Ithaca, Ne w York

Mark A . Matthew s University of Californi a Davis, Californi a

Donald L . Suare z USDA Agricultural Researc h Service Riverside, Californi a

Richard H . Niema n (retired ) USDA Agricultural Researc h Servic e Riverside, Californi a James W. O'Leary University o f Arizon a Tucson, Arizon a

Charles G . Suhayda USDA-Agricultural Research Servic e Pasadena, California

Robert E . Paull University o f Hawaii a t Mano a Honolulu, Hawai i Robert W . Pearc y University of California Davis, Californi a Albert C . Purvis University o f Georgi a Coastal Plai n Experiment Statio n Tifton, Georgi a Harvey A . Quamm e Research Statio n Summerland, BC , Canad a James D. Rhoades USDA Agricultural Research Servic e Riverside, Californi a Frank B . Salisbury Utah State Universit y Logan, Uta h

9

Michael C . Shannon USDA Agricultura l Research Servic e Riverside, Californi a

Karen Tanin o University of Saskatchewa n Saskatoon, Saskatchewan , Canada Ralph Weimber g (retired) USDA Agricultura l Research Servic e Riverside, California Chien Y i Wang U.S.D.A. Beltsvill e Agricultura l Researc h Center, Maryland Conrad J . Weise r Oregon Stat e Universit y Corvallis, Orego n Clyde Wilso n USDA Agricultura l Research Servic e Riverside, California Michael Wisniewski USDA Agricultural Researc h Service Kearneysville, Wes t Virginia Anne F . Wron a University of California Holtville, California

APPENDICES PRESENTING SCIENTIFIC DATA Anyone ca n d o experiments , bu t i f th e result s ar e t o qualif y a s science , mor e i s required tha n special techniques, logical thought processes, and elaborate equipment . It i s not th e whit e laborator y coat s an d foul-smellin g chemicals , o r eve n th e fiel d stations o r telescope s o r orbitin g satellites , tha t qualif y a work as science. T o b e science, the results o f one's investigations must be presented t o one's colleagues fo r their evaluatio n an d perhap s fo r the m t o us e in their ow n attempts t o expan d th e limits o f huma n understanding . Dat a mus t b e publishe d o r otherwis e presented . "Publish o r perish " may be thought of by some as an unfair deman d placed o n goo d teachers, but without publication (presentation) , a n investigation does not qualif y as science. Indeed , unles s th e result s o f one' s effort s ar e communicate d t o one' s colleagues, th e resources (ofte n ta x funds) use d to produce thos e result s ar e wasted. Presentation of data requires the use of language. Typically , results are described in a scientific paper, s o Appendix A is a discussion of writing. Th e discussio n doe s not emphasiz e th e usua l forma t o f a scientifi c paper (Introduction , Method s an d Materials, Results , Discussion) ; suc h a patter n i s wel l know n t o scientists , an d specific detail s can be seen in the journals t o which authors inten d t o submit thei r manuscripts. I t is imperative tha t authors consult such sources before preparing and submitting manuscripts . Th e discussio n her e present s som e principle s o f Englis h grammar and style. Althoug h spac e limitation s eliminat e a complete analysi s of the English language , a n attempt i s made to cover th e basic s in a somewhat logica l way and to emphasize a few points that often ar e not appreciated. Scientist s al l over th e world mus t now prepare som e o f their manuscript s in English even when English is not thei r nativ e language . Althoug h goo d cop y editor s kno w th e rule s discusse d here, many scientist author s apparentl y do not , an d fe w journals do an y extensive copy editing. Hence , it is easy to find example s in the curren t scientific literature of the problems describe d i n Appendix A . Data are als o communicate d at scientific meetings . Traditionally , this has bee n an oral presentation illustrate d b y slides. Durin g recent years , such slide talk s have included man y tex t slide s a s wel l a s th e traditiona l photographs , dat a graphs , diagrams, and othe r figures . Compute r program s have made it possible to prepar e beautiful an d elaborat e slides . Nevertheless , suc h talk s ar e sometime s poorl y presented an d poorl y received . Member s o f the audienc e ma y have to struggl e t o understand what is being discussed. I n many cases, communicatio n could be better achieved i f a few simple rules were followed durin g preparation and presentatio n of 161

162 Appendices the slides . Appendix B discusses many of these rules. Man y scientific societies no w emphasize poster s ove r ora l presentations , an d again, many posters ar e difficul t t o assimilate i n th e availabl e time. Thus , Appendi x B also discusse s some rules an d suggestions tha t can improve communication between a poster presenter an d his or her audience. W e recognize that writing styles, slide talks, and poster presentation s represent the personal expressions of their authors. B y the same token, Appendices A an d B represent persona l viewpoints. W e hope thi s wil l no t detrac t fro m thei r potential value . Plant scientists ofte n depen d upon growth chambers in their research , but ther e are many kinds of chambers and many ways that the experimental conditions ca n be reported. Thus , Appendix C presents guideline s fo r measurin g and reportin g th e environmental parameter s o f growth-chambe r experiments. Th e guideline s wer e formulated by a special committee of the American Society of Agricultural Engineers (ASAE). Th e guidelines are essentially an application of the principles presented in Section II . The y have been edite d slightl y to conform , a s far a s possible, t o othe r recommendations i n this book.

A SOME SUGGESTIONS ABOUT SCIENTIFIC WRITING Frank B . Salisbury Plant Scienc e Departmen t Utah Stat e Universit y Logan, Utah 84322-482 0 U.S.A . As a budding young scientist a t th e university , I found m y English classes t o be very distasteful. Ther e seeme d t o b e n o logic—n o science—t o the language , onl y a n assemblage o f arbitrary rules. The n I lived for two years in Switzerland and learne d German, a highl y logical language . Gradually , through analog y with the Germa n grammar I was enjoying s o much, I began t o se e som e glimmering s of logic in my native tongue. Later , a s I became involve d in text-book writing, the cop y editors at Wadsworth Publishing Company piqued my curiosity by the changes they made in my manuscripts. Wh y should which sometimes be changed to that, for example? I began to browse the style manuals and rule books, findin g a little more logic in the English language, ofte n burie d i n th e assemblag e o f arbitrary rules. For th e pas t fe w years, I hav e bee n editin g submitte d manuscript s fro m th e Americas an d Pacifi c Rim countrie s fo r the Journal of Plant Physiology . O f cours e there ar e special problem s face d b y authors whose native tongue is not English , and part of the discussio n her e has them in mind. Furthermore , not al l my fellow nativ e English speaker s se e th e structur e o f Englis h a s I do. Rule s o f punctuation , fo r example, base d o n th e logi c o f the languag e as I came t o understan d it an d a s th e manuals describe it, seem to be breaking down. Usag e continually changes the rules. What follow s summarizes my personal vie w of how the logi c of English can b e expressed wit h th e hel p of punctuation and a suitable choice of words. A s fa r as I know, my approach t o th e topi c i s unique although I can back up ever y rule with references t o the much more extensive manuals, and my discussion has been checked by three grammarians. I hope tha t you will approve of this approach and apply its recommendations. Tim e will tell ho w much usage will change the rule s and henc e my approach—and perhaps mak e th e language even more arbitrary and less logical ! Clearly, th e bes t communicatio n require s a n agreemen t o n languag e convention s between bot h reade r an d author . A prope r comprehensio n o f suitabl e writin g conventions i s essential, just as acceptance an d understanding are required for proper use of the othe r units , symbols, and term s presented in this book. T o this end, th e following i s offered . 163

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1. THE SENTENCE While i t may be impossible t o define a sentence i n a broad sense that will cover all example s (Pinckert , 1986) , a sentenc e i n technica l writin g is seldom difficul t t o recognize. Indeed , grammarian s recogniz e onl y six basic sentenc e structure s (se e box). A complet e sentenc e contain s a t leas t on e subjec t ( a noun) wit h it s verb (Plants grow. Jesus wept.), and most of the time it also includes an object of the verb along with modifying adjectives, adverbs, various phrases tha t act as modifiers, and often a conjunction tha t join s one word with another, one phras e with another , o r one claus e wit h another. Prepositions ma y be placed i n front o f nouns t o show the relationship o f the nou n to othe r word s in the sentence, an d pronouns (which, in a sense, are reall y nouns) ma y be used t o substitute for other nouns . Sometimes , bu t not ofte n i n technical writing , an interjection may be added although i t ha s no rea l relationship t o anything in the sentence . (A h ha, we discovered that plants grow.) A sentence may include any of the eight parts of speech (writte n in bold face above), bu t the key to recognizing a complete sentenc e is to recognize the subject and the verb. The verb i s needed fo r the predicate (what is being said about th e subject, including the verb wit h or without objects , complements , o r modifiers) . I f either th e subjec t or the verb is missing, the resul t is a sentence fragment (or an incomplete sentence) rather tha n a complete sentence . Writing elementary sentence s seldo m cause s any difficulty fo r a scientific writer, but problem s sometime s aris e whe n a sentenc e contain s mor e tha n on e subjec t and/or mor e tha n one verb. Shoul d tw o ideas, each with a subject and predicate, b e included i n on e sentence , o r shoul d the y be separate d int o tw o sentences ? Ho w should the relationship betwee n these ideas be formulated and expressed? Thes e are decisions tha t a n author mus t make in the attempt to best communicate what he or she wants to say. I t is essential t o kno w the availabl e options i f one i s to mak e th e best decisions. Th e relationship betwee n tw o ideas can be expressed at several levels , and thes e ar e indicate d b y various system s of punctuation. A. Closely Related; Subject or Verb is Shared. Man y authors , includin g technical writers , ti e togethe r (coordinate ) tw o subject-predicat e idea s wit h a coordinating conjunction and omit the subject before the second verb , knowing that the reader wil l refer to the original subject to understand the second predicate . Th e sentence just presente d provide s a n example . Th e subjec t is authors (modified by several words) , th e firs t ver b i s tie, an d th e secon d ver b i s omit, whic h als o ha s authors a s it s subject . Th e idea s ar e tie d togethe r b y the conjunctio n and, which coordinates th e tw o ideas . Coordinating conjunctions includ e and, but, or, nor, for, and so. Not e tha t th e firs t clause ( a group o f words with expressed o r understoo d subject an d predicate ideas ) i s independent because it has both a subject and a verb, while the secon d clause i s dependent on th e first . Th e secon d claus e i s dependen t because i t lack s a subject o f its own but depend s o n th e independen t claus e fo r it s subject (a s i n thi s sentence , followin g but). Som e dependen t clause s lac k a ver b instead o f a subject althoug h thi s i s less common . Th e questio n concerns ho w th e relationship between th e two ideas in such sentences should be communicated to th e reader b y punctuation. Sinc e bot h idea s shar e a commo n subject, the y are closel y related, an d logi c suggest s tha t n o comm a (n o paus e i f spoke n aloud ) i s neede d

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THE SIX SENTENCE STRUCTURE S I N ENGLISH The English sentence has six basic patterns. N o matter how complicated a sentence is, it can be broken dow n into one or more of these designs: 1.

subject verb

2.

subject verb + modifier s adjective adverb prepositional phrase

3.

subject verb

4.

subjective complemen t (eithe r a n adjective , noun, o r pronoun) subject verb object

5.

subject verb object indirect objec t

6.

subject I verb

objective complemen t object

Examples; 1. Jesus wept. 2. The dirty clothes are probably in the hamper. 3. I t i s cold. I t tastes sour. This is he. (Th e complemen t i s either an adjectiv e o r a nominative-case nou n or pronoun. ) 4. W e found him. Sh e measured the plant. (Th e object is always in the objectiv e case , a matter o f concern onl y with pronouns. ) 5. H e gave her the ring. (Th e indirect object, her, defines the recipi ent o f the actio n o f a transitive verb.) 6. Th e sight turned hi s hair grey. Th e speech made everyone angry. We elected him president (Th e objectiv e complement tell s what happened t o th e object a s a result o f the actio n o f the verb. ) This material was supplied b y Moyle Q . Rice .

before th e conjunction . Th e majorit y o f style manuals and rul e book s on Englis h writing agree (althoug h som e suggest that but is an exception an d should always be preceded b y a comma). It i s commo n practic e i n moder n writing , however , to inser t th e unneede d comma. Becaus e usage rathe r tha n logi c actually dictate s ho w w e shoul d write,

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adding th e unneede d comm a ma y now be so common tha t i t ca n hardly be called incorrect. I t i s usage tha t teache s a reader t o understan d the sam e convention s a s the author. Nevertheless , a reader seldom if ever fails to understand such a sentence with n o comm a just because th e comm a i s omitted . Therefore , i t i s logica l t o recommend, i n spite of increasing usag e to the contrary, that the comma between a dependent an d a n independen t claus e connecte d wit h a conjunctio n b e omitted . What i f the tw o clauses becom e s o long and complex that th e autho r strongl y feels a nee d fo r a pause an d want s t o inser t a comma to sugges t it ? The n th e comm a should probabl y b e added , bu t i t migh t be bette r t o brea k th e sentenc e int o tw o sentences or to go to one of the next levels by repeating the subject and making both clauses independent ; that is , avoid creating th e problem . Once the concepts are understood, punctuation should put onto paper what the author want s th e reade r t o feel . A comm a mean s a pause , an d suc h a paus e i s usually not needed if the second clause is dependent. Fo r example, one can read this sentence aloud an d ca n note that n o paus e is needed befor e the and. Th e subjec t (one) o f the first claus e carries over to the second, dependent clause. (Th e two verbs are ca n read an d ca n note; the secon d ca n could be omitted.) If you want to paus e for the sake of emphasis, the appropriate punctuation is a dash (called a n em dash), which was invented just to indicate a long pause that shift s the emphasi s to th e en d of the sentence . A dash (—) i s longer than a hyphen (-) or made on a typewriter with two hyphens (--); when used like this—it is usually not se t apart with spaces. I t is easy to overuse the dash-and thus to weaken its effect (lik e that). Furthermore , dashe s ar e seldom use d in scientific writing. A s a punctuation mark, the das h convey s a certain emotion , an d emotion mus t generally be avoide d in technical writing. Som e grammarians suggest that the dash should never be used . B. Closely Related Independent Clauses Connected by a Coordinating Conjunction. Ofte n two more-or-less equal ideas, each expressed with both subject and verb, are tie d togethe r (coordinated ) wit h a coordinating conjunction. I n this case, bot h logic an d th e styl e manuals (especiall y i n America ) sugges t th e us e o f a comm a before th e connectin g conjunction , and usag e agai n seems t o b e goin g toward n o comma. Nevertheless , th e recommendatio n i s to us e the comma . I used i t i n th e sentence about styl e manuals and usage , and her e i t i s in thi s sentenc e a s well. I doubt tha t anyon e will be upset. Th e rule books generall y say that short , indepen dent clause s following a conjunction do not need the comma before the conjunction and tha t make s some sense. (Di d I need a comma before that last and ? Probabl y not.) Thus , ther e i s som e leewa y i n th e us e o f a comm a befor e a coordinatin g conjunction connectin g independen t clauses , but a s a general rule, that comma can be helpful. I t should b e use d mor e frequently than it is. There are times when it is needed for clear understanding. Without it, a reade r may hav e t o bac k up , star t again , and realiz e onl y on th e secon d readin g tha t th e noun followin g th e conjunctio n wa s th e subjec t o f a secon d independen t claus e instead of the secon d object of the firs t clause : W e measured the auxin and gibberellin was present but was not measured. I t would be wel l t o recas t tha t sentence , bu t a comma afte r auxin would help i t a s it stands.

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7

C. Closely Related Sentences (no Conjunction). Sometime s an author wants to show that tw o sentences ar e closel y related; the y may not be related closel y enoug h to connect the m with a conjunction, however. I n such a case, one has the option of simply writing two sentences, eac h terminate d with it s own period, or on e ma y put a semicolon between them , as in the previous sentence. O f course, there ar e othe r possibilities. Woul d the opening sentence hav e been better this way: Sometimes an author wants to show that two sentences are closely related, but they may not be related closely enough to connect them with a conjunction. Tha t is, those two ideas could have been coordinate d wit h the conjunctio n but. There ar e tw o kind s o f error s tha t appea r i n thi s situation . Bot h shoul d b e avoided. Th e firs t i s the comma fault (o r comma splice) in which the tw o complet e sentences are connected wit h a comma but no conjunction. Thi s is considered a fatal error by all editors, it must be avoided under all circumstances. ( I hope you caught it just now. ) The secon d erro r i s being supporte d b y some limited usage; indeed, ther e is a tendency for scientific authors to feel tha t they are being especially "scientific" when they use however instead o f but: An author may want to show that two sentences are closely related, however they may no t b e related closel y enough to connect them with a conjunction. Word s lik e however, rather, nevertheless, thus, indeed, an d other s ar e connectives an d no t conjunctions . The y ar e als o calle d conjunctive adverbs; they both modif y an d connec t a t th e sam e time . The y are punctuate d as interjections . Thus, i f the autho r fel t compelle d t o us e however i n tha t sentence , i t shoul d hav e been punctuate d lik e this: A n author may want to show that two sentences are closely related; however, they may not be related closely enough to connect them with a conjunction. Tha t is, the second par t of the compound sentence (afte r the semicolon) shoul d be punctuated in the sam e manner as when a conjunctive adverb begins a sentence: However, they may not be related . . . . I n general, however, an author should realize that overuse of such connectives sounds stuffy, affected , professorial—an d scientific, if that is what usage has taught us. Nevertheless , writing can often b e greatly improved by eliminating such words. Surely , a reader deserve s th e credit for being able to see the connection between ideas without such unneeded "help." (Were connectives overused in thi s paragraph ? Probably. ) D. Les s Related Sentences. Thes e ar e separate d with periods. O f course they are no t unrelated , whic h i s wh y the y ar e combine d togethe r i n a paragraph . Separation wit h period s i s th e usua l an d appropriat e wa y o f writing , bu t i t i s important to have the other levels at one's fingertips in case they better communicat e an author' s ideas . Bu t avoid th e comm a fault ! E. Two Ideas are Connected with a Subordinating Conjunction. W e have been discussing situations i n which two ideas ar e about equal to each other an d are tie d together i n various ways (comma, semicolon) or not at all. I n another situation, two clauses o f unequal importance are tie d together in the sam e sentence b y a subordinating conjunction. Ther e ar e man y kinds of subordinating conjunctions including relative pronouns (that, which, who) and conjunction s of tim e (after, since, before, when, while, as, and until), place (where, wherever), purpos e (so that, in order that), comparison (than, as, a s if , but if , as though, whereas), condition (if, unless), conces -

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sion (although, though, even though), and caus e (because, since, and th e weake r for and as). An y of these and other s ca n be used to show how the subordinat e claus e relates t o th e mai n clause . Changin g tw o coordinat e clause s connecte d wit h a conjunction t o a mai n claus e wit h it s subordinat e claus e ca n ofte n clarif y an d generally improv e th e writin g (Pinckert, 1986) . Th e easy way is to us e coordinat e clauses. A better way, although on e tha t require s som e menta l effort, i s to clarif y relationships b y forming subordinate clauses. S o that it does not sound like an after thought, i t ofte n help s t o pu t th e subordinat e claus e firs t (a s i n thi s sentence) . Consider thes e tw o sentences: Galleys should b e returned t o the editor after they have been carefull y read. After th e galleys have been carefully read, they should b e returned to the editor. The rul e fo r punctuatin g between a mai n clause an d it s subordinat e clause i s simple: I f the subordinat e claus e comes first , i t i s followed b y a comma; if it comes after th e main clause, it is not. ( . . .it is not i f it comes after th e main clause.) Becaus e a subordinate claus e shoul d never stand alone (formin g a sentence fragment rathe r than a complet e sentence) , i t mus t alway s occu r i n th e sam e sentence a s it s main clause. Thi s means that it should not be separated fro m a preceding main clause by a comm a o r semicolon. Tha t i s the rule , althoug h it sometimes seems appropriat e to ad d th e comm a fo r emphasi s (a s was done here). I n the mos t informal writing, an author ca n add a dash to provide strong emphasis on th e subordinate phrase o r clause—although dashe s ten d t o b e overuse d b y writers who ar e insecur e i n thei r knowledge o f punctuation. Whe n in doubt , add a dash! O f course thi s should be avoided. There is a complication. Som e subordinating conjunctions (e.g., although) can be used a s conjunctive adverbs . I n such cases, punctuation should follo w th e rule s described abov e fo r such conjunctiv e adverbs. F. Beginning a Sentence with a Coordinating Conjunction. A t leas t on e important questio n remains : I s it correc t t o begi n a sentenc e with a coordinating conjunction (and, but, etc.)? Becaus e coordinating conjunctions are normall y used to splic e together tw o clauses, they cannot come at the beginning of the sentence if both clause s ar e presen t (a s th e subordinatin g conjunction because di d i n thi s sentence). Bu t what abou t a sentenc e tha t begin s with a conjunction but contain s only one clause ? Sometimes , for emphasis, an author may want to arbitrarily make two sentence s ou t o f a compoun d sentenc e tha t ha s a coordinatin g conjunction between tw o independent clauses . Doin g so ties th e sentenc e tha t begin s with th e coordinating conjunction to the thought of the previous sentence mor e closely than would be th e cas e without the conjunction . I t i s acceptable t o begin a sentence with a conjunction. An d sometimes it can provide impact. I n thi s case, th e coordinatin g conjunction act s more lik e a conjunctive adverb. Bu t like many devices of this type, it ca n be overdone . I t should be use d with care. 2. MODIFYING WORDS For th e mos t part , the us e o f modifyin g word s is relatively eas y in th e Englis h language, but a fe w problems arise.

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9

A. Adjectives. Adjective s ar e words that modify (explain ) nouns and pronouns . Because the y ar e no t decline d accordin g t o gende r an d cas e a s i n man y othe r languages, thei r us e i n Englis h i s quit e simple . Th e fe w problems tha t appea r i n technical writin g concer n us e o f th e hyphe n i n compoun d adjectives , us e o f th e comma when mor e tha n on e adjective modifies a noun, and distinguishing between adjectives an d adverbs . (Som e language s don't us e articles, which are special adjec tives tha t limi t or give definiteness t o the things represented b y the noun. A an d an are indefinit e articles ; th e i s th e definit e article: A beaker says ther e i s onl y on e beaker bu t doesn' t specif y whic h one; th e beaker an d the beakers refe r t o a specifi c beaker o r beaker s tha t ma y have already been mentioned. ) A compound adjective consists o f two or more words that act as a single idea t o modify a noun . Th e compoun d adjectiv e i s usuall y formed b y placin g a hyphe n between th e tw o or mor e word s ( a four-year-old tree). The tw o words migh t bot h b e adjectives, on e migh t be an adjectiv e an d on e a noun, or both might be nouns, but the combination acts as an adjective: a cold-water shower. Eve n adverb s ca n b e par t o f compoun d adjectives . T o qualif y a s a com pound adjective , th e word s mus t ac t togethe r i n a specia l wa y rather tha n eac h modifying th e nou n independently . Far-red light provide s a good example . W e ar e not talkin g about a distant, re d light ; instead, we are discussin g light in th e far-red part o f th e spectrum . Usually , when tw o or mor e adjective s precede a noun, eac h modifies th e nou n independently: a bright, red, metal-halide lamp. Thes e are calle d coordinate adjectives, and i n the example, one i s a compound adjective that consist s of tw o noun s (metal an d halide) actin g togethe r a s a n adjectiv e that describe s th e lamp. It i s sometimes difficul t t o kno w whether a comma should b e use d betwee n a series of coordinate adjectives . Curren t usag e often tends to eliminate commas, bu t in technica l writin g i t help s t o us e them . I f there ar e mor e tha n tw o coordinat e adjectives, comma s become mandatory; if there ar e onl y two, a helpfu l devic e i s t o see whether th e insertio n o f and i s acceptable. I f it is, the tw o adjectives ar e quit e independent o f each other , an d th e comm a should be added. I f the and sounds ou t of place , the tw o adjectives ar e relate d t o eac h othe r almost as they would be in a compound adjective; th e comma should be omitted. I f a bright and green light doesn' t sound right , leav e ou t th e comma : a bright green light. I f a ho t an d re d light i s acceptable, us e the comma : a hot, red tight. Clearly , the distinctions can be fine, an d decisions mus t be lef t t o th e author , bu t th e author mus t be aware of the accepte d conventions. Two words in a compound modifie r might be an adjective and a noun, with th e adjective an d th e nou n actin g together t o modif y anothe r noun : a short-day plant. This doe s not sa y that th e plan t i s short o r tha t i t is a day plant but tha t th e plan t responds t o short days. Not e tha t the combination short days b y itself does no t for m a compound adjectiv e but i s simply a case of short acting as an ordinary adjective t o modify th e wor d day. Th e hyphe n i s appropriate onl y whe n the combinatio n acts together as an adjective to modify another noun (which is sometimes implied but no t stated: irradiate th e seeds with far-red).

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It is appropriate in scientific writing to combine a number (an adjective) with a unit (a noun) t o form a compound modifier when the number and unit are written out: a four-hour night, a ten-milliliter aliquot, a five-gram sample, etc. (But , note : four hours, te n milliliters, fiv e grams, etc.) A s discusse d i n Chapte r 1 , however, whe n numerals and unit symbols are used, the hyphen should be omitted. Thi s i s because the uni t symbo l shoul d b e though t o f a s a mathematica l symbo l tha t stand s fo r a physical quantity . Thus , a 0. 5 kg sample i s th e mas s o f th e standar d kilogra m i n Sevres, France , multiplie d b y 0.5 . Us e o f th e hyphe n destroy s thi s relationship . When numerals an d symbols are spelled out , the rules of grammar apply; when thei r symbols ar e used , mathematica l rule s apply . Sometimes tw o or eve n thre e nouns ac t together a s an adjective. Logic would suggest tha t the y shoul d b e connecte d wit h a hyphen , but usag e ofte n make s th e hyphen see m ou t o f place: cell-wall materials or cell wall materials'? Mos t author s would us e the secon d form , and most editors woul d probably change th e firs t t o th e second form . Bu t stan d u p fo r logi c i f you fee l s o inclined, eve n i f your creation is likely to b e changed b y an editor. Adjectives ca n b e th e presen t o r pas t participle s o f verbs, i n which for m the y often appear i n compound adjectives, especially in scientific writing: a light-controlled switch (past participle); a light-controlling switch (present participle). Not e tha t th e meanings ar e differen t i n these two cases. I n the first , ligh t controls th e switch ; in the second , th e switc h control s th e light . Althoug h thes e form s ar e commo n i n technical writing, the comparable longer constructions ar e often easier to understand: a switch that light controls; a switch that controls the light. To summariz e som e recommendation s fo r th e us e o f hyphen s i n compoun d modifiers: D o no t us e wit h a combinatio n o f number s an d unit s tha t modifie s a noun ( a 100 W lamp). Us e with nearly all other compound modifiers; this will make it easier for most reader s an d offen d onl y those who have decided tha t punctuatio n should be eliminated jus t for the sake of eliminating punctuation. Avoi d adding th e hyphen between som e compoun d modifier s that ar e ofte n see n withou t i t (the high school reunion), usually consisting o f two nouns rather than an adjective and a noun. Do no t us e a hyphen betwee n a n adver b and an adjectiv e if the adver b ends i n -ly . Otherwise, compoun d adjective s tha t include adverbs are often hyphenated : a welldone steak (bu t a steak that wa s well done), a well-known expert, a loose-fitting garment (bu t a loosely fittin g coat), a well-guarded secret (bu t a carefully guarded secret). Al l compoun d number s ar e hyphenate d (sixty-seven samples and there were only sixty-seven), bu t chemica l term s neve r are : hydrogen sulfide gas. Some word s hav e prefixe s or suffixe s tha t ar e alway s hyphenated: self-rule, ex husband. Other s ar e combine d wit h th e wor d an d neve r hyphenated : overdose, underground, coworker. Whe n i n doubt , consult a dictionary. B. Adverbs. A n adverb can modify verbs, adverbs, and adjectives; it is a versatile part o f speech. I f a modifie r is modifying anythin g but a noun or pronoun , i t i s an adverb. Adverb s tell where, when, how, or how much. Man y adverbs end i n -ly, but many do not, an d not al l words ending in -ly are adverbs. Mino r trouble arises when adverbs and adjective s are confused , bu t thi s occurs most often i n speech an d no t i n technical writing. W e naturally write: Th e good experiment wa s done well. Not : Th e

Some Suggestions About Scientific Writing 171

well experiment wa s done good. Well i s the adver b that modifies the verb was done, while good i s the adjectiv e tha t modifie s the nou n experiment, Note tha t sense-impression verbs ar e followe d b y th e adjectiva l rathe r tha n adverbial forms : I t tastes good. I t smells bad. H e looks sick. I feel ba d (rather tha n I feel badly) . I feel good. ( I feel well means that I feel healthy rather than sick if well modifies I-o r tha t I have a good sens e of touch if well modifie s feel.) A word o f warning about adverbs : Man y writers seem t o have the notio n tha t adverbs ar e ver y elegant, bu t ofte n the y are inherentl y vague. Ho w elegant i s very elegant? Ho w vagu e i s inherently vague ? W e ca n ofte n tighte n ou r writin g by eliminating very, too, greatly, really, actually, extremely, quite, rather, slightly, fairly , somewhat, t o a certain extent, and ver y man y others! O f cours e thes e word s ar e sometimes useful . C. Prepositions and the Objective Case. Englis h is relatively easy for foreigners to lear n (t o begi n with , a t least ) becaus e nouns , a s wel l a s adjectives , ar e no t inflected accordin g to case and gender. Thi s means that there are few problems with the us e o f prepositions, whic h ar e word s tha t ar e place d i n fron t o f noun s an d pronouns t o sho w the relationshi p o f the nou n to other words in the sentence : fil l to the calibratio n mark , for a good reason , behind th e scutellum , with care, between the lines , etc . Noun s followin g preposition s ar e alway s i n th e objective case, bu t since English noun s have the same form in the subjective and the objective cases, we seldom give the matter any thought. Tha t is probably why we may have trouble when we use Englis h pronoun s tha t d o have a special for m i n th e objectiv e case. Ther e are onl y si x of the m i n moder n English : me , him, her, us, them, an d whom (plu s whomever and th e obsolet e thee). 1 We seldo m hav e troubl e whe n th e nou n follow s th e prepositio n directly , bu t many Americans (wh o seem to have little sense of case because it is such a small part of the language ) say between you and I instead of the correct between you and me, an d it i s not uncommo n t o hea r with we girls instea d o f with us girls. Direc t o r indirec t objects o f verb s ar e als o i n th e objectiv e case : H e gave her the unit, an d it s probe contacted him an d me. I n technical writing, we use fewer personal pronouns anyway, but w e must be careful when we do use them. D. Personal Pronouns. A s a matte r o f fact , w e shoul d probabl y us e mor e personal pronoun s i n our scientifi c writing. I t is highly artificial t o put ou r writing always i n th e thir d perso n b y saying the author did thi s or tha t instea d o f simply saying / o r w e did it. Man y modern editor s ar e no w insisting on the firs t perso n instead o f the out-of-date third person. Fo r one thing, an author should be willing to tak e responsibilit y fo r his or he r experimenta l results and philosophica l sugges tions by speaking i n th e firs t perso n instea d of hidin g behind some almos t anonymous author who seems t o be doin g the writing. Sayin g the author doesn't mak e a paper an y more objective .

The subjective form s are /, he, she, we, they, who, an d thou; possessiv e forms are my, mine, his, her, hers, its, our, ours, their, theirs, whose, and thine; it and you ar e th e sam e in the subjective and th e objective cases .

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3. MODIFYING PHRASES AND CLAUSES A. Restrictive and Nonrestrictive Phrases and Clauses. Problem s encountered with phrase s ar e mostl y concerned wit h how they should b e punctuated. Ofte n th e author must decide how to punctuate, depending on the exact meaning that he or she wants t o convey . Th e ke y to makin g th e decisio n correctl y i s t o understan d th e concept o f th e restrictiv e versu s th e nonrestrictiv e phras e o r clause . A restrictive phrase o r claus e contain s informatio n that i s essential t o understandin g some par t of th e sentenc e no t include d i n th e phras e o r clause ; a nonrestrictive phras e o r clause add s informatio n tha t ma y well b e importan t bu t tha t i s no t essentia l t o understand th e part s o f the sentenc e no t include d in the phrase o r clause . These two possibilities can often be illustrated with the same sentence, whic h is why th e autho r mus t decide whic h one expresse s hi s or he r intention . M y son, the doctor, sent me a letter. Th e doctor i s a nonrestrictiv e phrase tha t suggest s that th e speaker has onl y one son , who happen s t o b e a doctor. M y son the doctor sent me a letter. I n this case, the speake r ha s more tha n one son, but th e restrictiv e phras e the doctor tell s whic h so n sen t th e letter . Th e differenc e i s th e punctuation . Nonrestrictive words , phrases, or clause s are se t off by commas; restrictive one s ar e not. Her e i s another example : Th e girl standing in the garden waved t o him. Yo u can identif y th e gir l only by knowing that sh e was standing in th e garden . Th e girl, standing in the garden, waved t o him. I t happens that the girl who waved was standing in the garden , a bit of interesting bu t nonessentia l information. In correc t application , th e us e o f the relative pronouns which o r that depend s upon whether the claus e tha t is introduced i s restrictive or nonrestrictive . Which i s the nonrestrictiv e relativ e pronoun ; that i s restrictive . Th e automobile that wa s speeding wa s completely destroyed. T o kno w which automobil e wa s destroyed , w e must know that it was speeding. Th e automobile, which was speeding, wa s completely destroyed. Th e importan t thing that the sentence tell s us is that the automobile-no question whic h one-was destroyed; a s it happens , it was speeding. I n our reading , we gain the sens e of whether a phrase or clause is nonrestrictive or restrictive b y the use or omissio n o f the comm a or commas . Whe n ther e ar e relativ e pronouns , th e use of which or that fortifies tha t sens e o f restrictiveness o r nonrestrictiveness . In scientific writing, most phrases or clauses introduced by relative pronouns are restrictive; suc h phrase s shoul d b e introduce d b y that without a preceding comma . When a n occasional nonrestrictive phras e or clause is used, it should be introduce d by which, proceeded b y a comma. T o improve one's writing, an author should engage in a "whic h hunt," replacing restrictive whichs with thats. This seem s lik e a simpl e enoug h rul e t o follow , an d i n scientifi c writing th e concept o f restrictive o r nonrestrictiv e can often conve y important information that an autho r migh t want th e reade r t o comprehend . Judgin g by published technica l articles, however , man y authors an d editor s ar e unawar e of th e rule . I t i s onl y consistently followe d in the best-edited , non-technica l magazines or books. Appar ently man y writers hav e th e mistake n idea tha t which i s more forma l tha n that an d thus shoul d be use d i n th e mos t formal o r technica l writing. Th e us e of thes e two relative pronoun s ha s littl e o r nothin g t o d o wit h formality ; i t i s al l a matte r o f restrictiveness o r nonrestrictiveness . Th e recommendation is to follo w th e rul e but

Some Suggestions About Scientific Writing 17

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not t o get too upse t when others fai l t o follow it. Perhaps , as the years go by, it will be adhered t o by more an d more author s an d editors . That an d wh o provid e anothe r pai r o f relativ e pronouns . Again , th e rul e i s simple, and agai n it is often broken. Wh o should be used with reference t o people; that i s used fo r everythin g else. A claus e beginning with who (o r whom if it i s th e object of a sentence or a preposition) ca n be restrictive or nonrestrictive; us e of the comma tell s when it i s nonrestrictive . Nonrestrictive introductory phrases o r phrases a t the end of a sentence should be set of f from th e rest of the sentenc e wit h a comma in formal writing. Usag e has led to the omission of this comma when the phrases are short, but more frequent use of a comma to set off introductory or final phrases would lead to clearer writing. A s reading experience demonstrates, th e sligh t break or pause indicated b y the comma often contribute s t o eas e of understanding, as in this sentence. The discussion o f how to punctuate nonrestrictive phrases o r clauses brings up a logica l rul e tha t i s often violate d b y modern writers: Put a pair of commas, or none, between subject and verb, or verb and object, or subjective complement. T o say it anothe r way : A subjec t an d it s ver b shoul d neve r b e separate d b y a singl e comma (unless the comma occurs between coordinate adjectives). I f subject and verb are separate d b y a nonrestrictiv e phras e or clause, there mus t be two commas that surround th e phras e o r clause . Th e rul e is broken, especiall y i n technica l writing, because the subject may be modified with so many words and phrases that the author feels the reader will run out of breath by the time he or she gets to the verb; the rest afforded b y a comma seems t o b e in order. Bu t this comma will be very distracting to a reader who is really paying attention. Th e reader i s anticipating the action, th e verb, an d i s confuse d b y bein g tol d t o paus e jus t befor e gettin g ther e whe n n o nonrestrictive (parenthetical ) materia l justifie s th e pause . Th e sample that ha d a large, green leaf attached to the brown stem with an expanded petiole base but virtually no thickened cuticle or acute lobe was chosen for th e herbarium. Some author s might be tempte d t o pu t a comm a befor e th e was. O f course , th e sentenc e woul d b e improved b y recasting i t a s two sentences . B. Parenthetical Phrases or Clauses. Nonrestrictiv e phrases or clauses (as just described) ar e parenthetical, which is to say that they contribute important informa tion but are not essential t o understand the rest of the sentence or to its grammatical structure. I f the sentence is correctly constructed, the parenthetical phrase or clause can be removed (alon g with the punctuation that sets it apart, the parentheses i n this case), and what remains will still be a grammatically correct sentence . Parenthetica l phrases ca n be punctuated i n four ways: wit h commas (as we have been discussing) , with parentheses2 (round brackets), with brackets (square brackets), and with dashes. The choic e belong s t o th e author , bu t th e choic e ca n conve y an author' s feelin g about th e parenthetica l material . I f commas ar e used , th e informatio n i s closel y related t o th e sentence , almost restrictive , we might say. 2 In Britain and other United Kingdo m countries, the term parentheses is generally applied simply to portions of text that are parenthetica l while bracket is a generic term for all parenthetical symbols: round brackets ( ) , square brackets [ ] , curly brackets{ } , and angle d brackets< > .

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If parentheses (round brackets) are used , the materia l is more of a side issue . It is important (or it would not be included at all), but it is not as closely related t o the res t o f th e sentenc e a s would be th e cas e whe n commas are used . Use d to o often, parentheses ca n be distracting, always confronting the reader with extraneous information tha t may seem beside th e point. Thi s feeling can often be changed just by changin g som e parenthese s t o commas . I f th e informatio n reall y i s almos t unrelated t o th e res t o f th e sentence , however , i t shoul d be in parentheses , an d a long sentence can sometimes b e made easier t o understan d by placing some of th e material i n parentheses. I n a sense , thi s removes it fro m th e sentenc e althoug h it might remai n exactly where it was. (Th e material might also be moved somewhere else.) Brackets [square brackets] are ofte n reserve d i n forma l writing for comment s inserted by an editor. Th e editor can be the author if he or she is quoting someone else but needs to insert an explanation or comment in the quoted material. Bracket s can also be used as parentheses within parentheses: Evans and an assistant (Gillespie, who made her own study of a flightless bird [the kiwi] in Australia) spent several difficult months in the field. Dashes are much less formal and should seldom if ever be used in technical writing-unless the autho r feels justified i n adding the stron g emphasis provided by use of the dash or dashes-and if the author is confident that the editor will not remov e the dashes ! I f comma s ar e include d i n a phras e se t of f with dashes, th e dashe s become essential . (Th e exclamatio n poin t i s als o seldo m use d i n technica l writ ing-for th e sam e reasons dashe s are seldom used!! [ I tend t o overus e both!] ) Two point s abou t parenthetica l materia l nee d t o b e noted : First , sinc e al l parenthetical material is by definition nonrestrictive, parenthetical phrases (regardless of how they are punctuated) that are introduced by a relative pronoun should always use which (o r wh o o r whom) instea d o f that. Second , sinc e i t shoul d alway s b e possible t o remov e a parenthetical phras e or clause without affecting th e structur e of wha t i s left , a n autho r mus t neve r us e doubl e commas , (lik e this) , aroun d parentheses o r brackets . Where i s the perio d place d i n relatio n t o material in parentheses o r brackets ? If th e materia l i n parenthese s come s a t th e en d o f a sentenc e an d i s itsel f a n incomplete sentenc e (sentenc e fragment) , th e perio d i s place d outsid e o f th e parentheses (lik e this) . I f the materia l i n th e parenthese s come s a t th e en d o f a sentence but b y itself forms a complete sentence, then such a parenthetical sentence should b e se t withi n its ow n parenthesis . (I n suc h a case , th e firs t lette r o f th e parenthetical sentenc e should be capitalized, and a period shoul d be placed a t th e end o f th e sentenc e an d befor e th e las t parenthesis , lik e this. ) Ther e i s n o rul e saying tha t parenthetica l materia l must be included in some other sentence ; it can and often should stand on it s own, as in the example . Ther e i s also no rule saying that parenthetical material cannot form a complete sentence within a sentence (it can be distracting , as here, so i t i s well to avoi d the practic e when possible), bu t i f th e complete-sentence, parenthetica l material can be placed after it s "parent sentence," it migh t just as well be give n a lif e o f it s own, cut of f from it s parent . Whe n it i s included within another sentence, i t is not punctuate d as an independent sentence .

Some Suggestions About Scientific Writing 17 4. VERB S

5

A. Plural an d singula r verbs . Plura l verbs must be use d with plural subjects , singular verbs with singular subjects. Tha t is , a verb must agree with its subject i n person an d number . A subject consisting of two or more singular nouns connected with and is plural: One nou n an d anothe r nou n mak e a plura l subject . I f tw o singula r noun s ar e connected by or, the subjec t is singular (but plural if the nou n closest t o th e verb is plural). A singula r subject followe d b y a modifyin g prepositiona l o r othe r phras e tha t contains plura l nouns or more than one singular noun is nevertheless singular (as in this sentence and the on e that begin s the previous paragraph). Some nouns taken from language s other than English form thei r plurals in ways that ar e no t alway s familiar; watch for these (datum an d data, medium an d media, etc.; se e Section 8) . B. Ver b tense. Ver b tens e should be consistent. I t is usually logical to use th e past tens e i n describin g methods , materials , an d result s i n a scientifi c paper: W e found that applied LA A strongly promoted elongation o f intact pea plants. Th e experiments were done in the past, and it is conceivable that they might give different results i f repeate d (i f al l determinin g condition s ar e no t know n or understood) . Hence, th e hones t wa y to describ e the m i s to us e the pas t tense . Avoi d changin g tense i n th e middl e o f a descriptio n o f method s o r results , usuall y i n a singl e paragraph. Publishe d result s ma y be described wit h the presen t tense : Yang e t al. (1993) showed that a continuous supply of auxin enhances stem elongation in intact plants. C. Participles. Englis h form s a present participle by adding -ing to the infinitive of th e verb . Thi s i s combined wit h som e for m o f th e ver b to b e to emphasiz e a n action tha t i s occurring (or tha t was occurring or has been occurring or will be occurring). Thi s i s such a n importan t par t o f the Englis h languag e that nativ e speakers virtually neve r use it incorrectly , but it is ofte n difficul t for writer s whos e nativ e tongue i s not English . Th e tendenc y is to us e this verb form to o often , when i t is not needed . Eve n nativ e speakers ca n frequently tighte n their writing by changing to th e simpl e form s (i t occurs, occurred, has occurred, will occur, for example) . A special problem i s the dangling participle, whic h is a participle that cannot b e connected immediatel y an d unmistakabl y with th e word(s ) t o whic h i t refers . Because the antecedent of the verb is often left to the reader's imagination, sentences with dangling participles ca n often b e quite ludicrous: Coming into the greenhouse, the large skunk cabbage gave off a n overwhelming stench. (Wh o entere d th e green house? Th e writer or th e skunk cabbage?) English usuall y forms a past participle b y adding -ed to the verb and combining it with another auxiliar y verb, usuall y a for m o f to have. Thi s verb for m indicate s that a n actio n wa s begun i n th e pas t relativ e t o th e tim e being referre d t o bu t i s completed i n that time being referred to, which can be the present, the past, or even the future : I have measured. Sh e ha s measured. H e ha d measured. Yo u will have measured. Th e pas t participl e can usuall y b e replaced wit h a simple past o r futur e form: / measured. Sh e measured. H e measured. Yo u will measure. Nevertheless , it

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is sometimes appropriate t o us e the past-participl e form . Thi s for m usuall y causes no trouble for native speakers unless the past participle is irregular or differs from the simple past , also formed by adding -ed. Example s o f irregular form s include: / give it. I gave it. I have given it. I do it. I did it. I have done it. She comes home. She came home. Sh e has come home. H e goes. H e went. H e has gone. Consul t a dictionary i f in doubt abou t th e pas t participle . D. Passive voice. Author s o f journa l article s ofte n us e th e passive voice by combining th e pas t participl e o f a transitiv e verb with any form o f the ver b t o be: The water potential was measured. Thi s constructio n omit s th e perpetrato r o f th e action, th e on e wh o did th e measurin g in th e example . Th e first-perso n persona l pronouns ar e avoide d s o the writing may seem mor e objective o r "scientific. " (Di d you catc h th e passiv e voic e i n tha t sentence? ) Actually , us e o f th e passiv e voic e allows one t o avoi d responsibilit y fo r one's actions, to divorce th e worker fro m hi s or he r work . Tr y t o us e th e active voice: Instea d o f saying, the leaves were treated (passive voice), say we treated th e leaves (activ e voice) .

5. SOME FURTHER NOTES ABOUT PUNCTUATION

The discussio n s o far has followed my "logical" approach t o the structur e o f th e English languag e with its simple-to-compound sentences , restrictiv e an d nonrestric tive modifier s (word s an d phrases) , an d specia l ver b forms . Thi s discussio n ha s placed man y items of punctuation int o tha t "logical " context, but severa l important although ofte n arbitrar y rule s di d no t fi t int o tha t evolvin g but somewha t limited discussion. Thu s th e followin g brie f outlin e (based o n Pinckert , 1986 ) summarizes the importan t rule s o f punctuation ; item s alread y discusse d i n som e detai l ar e presented i n small type :

A. Avoi d sentence fragments (incomplete sentences terminated with a period), and do not use a comma when a perio d (o r semicolon) shoul d be used; that is, avoid the comm a fault .

B. En d question s wit h a question mark, but d o not us e a question mar k with indirectly quoted questions: Sh e asked wh o Bob was. C. Reserv e th e exclamation point for tru e exclamation s o r command s (Drop dead!), which are seldo m use d i n technical writing ! Whe n the exclamatio n point is used fo r emphasis , a reade r soo n get s tire d o f suc h exclamator y writing! It s us e suggests sentence failure! Avoi d using the exclamation point just for emphasis! (Bu t its use in the last sentenc e is valid because that is a direct command, an imperative.) D. Use th e semicolon: — betwee n independen t clause s not connecte d with a coordinatin g conjunction .

— t o separat e comple x items in series whe n each item itself consists of a serie s of items : These ar e important plant hormones: auxin, typically a stem growth promoter; the gibberellins, also promoters of stem growth; cytokinins, stimulators of cell division; and ethylene and abscisic acid, sometimes called stress hormones. E. Use commas: - betwee n item s in a series, including before the and that precedes the last item : The equipment included a camera, portrait lens, an d flash attachment. Thi s serial comma, as i t i s called , i s ofte n omitte d b y moder n writers . Mos t manuals still recommend its use.

Some Suggestions About Scientific Writing 177 - afte r man y adverbs, phrases , an d clauses tha t introduc e a sentence an d are followed by a voice pause : T o avoid precipitation, it is essential to stir continually. — t o enclos e nonrestrictiv e phrases and clauses. — befor e a coordinating conjunction introducing an independen t clause.

— t o se t of f direct addres s and othe r parenthetica l interrupters . "Carol, will you fix breakfast?" - t o introduce o r interrupt shor t quotations . "Not," sh e said, "on your life." — t o preven t misreading . "Let's talk about Prof. Jones, and good scientists." Suc h style commas can be inserted t o emphasize an adverb (She snored, heavily.) o r to giv e extra emphasis t o modifier s of equal importance .

F. Use th e dash t o indicat e an extende d paus e an d giv e emphasis—bu t seldo m i f at al l i n technical writing. G. Use commas, parentheses, dashes, and brackets to se t of f parenthetical material.

H. Use ellipses ( a serie s o f thre e periods ) t o sho w tha t somethin g ha s bee n omitted fro m a quotation. I f the ellipses come at th e end of the sentence, add th e fourth period. Us e brackets [square brackets] to show that something was inserted by an editor. I. Whe n use d a s a mar k of punctuatio n within a sentence , a colon mean s as follows, a n example follows, here i s th e explanation o r list, or here i s what he o r sh e said. Whateve r follow s a colo n refer s back to wha t immediately preceded it . I t is logical t o us e a capital lette r afte r a colon i f a complete sentenc e follows , but many editors wil l chang e th e capita l lette r t o lowe r case . I f a lis t follow s a colon , th e words ar e no t capitalize d unles s the y ar e prope r noun s o r mus t otherwis e b e capitalized. Th e colon i s also use d in several other ways in scientific writing as ofte n noted i n this boo k (e.g. , t o sho w the proportion s o f components i n a mixture used in chromatography : water:aceti c acid:butano l 5:1:3). J. The apostrophe i s use d t o for m contraction s (don't worry) an d possessive s (Joule's book; originally a contraction o f Joule his book). I f the possessiv e i s a plural ending i n s o r a z sound , th e apostroph e come s afte r th e s ; some manual s suggest adding another s , but becaus e ther e is so much disagreement, thi s can be a matter of persona l choice . On e suggestio n i s tha t th e s should b e adde d i f i t i s easil y pronounced: Descartes's essays (becaus e neithe r s i s pronounced i n Descartes). Usually the extr a s is not adde d in technical writing. Indeed , contractions ar e use d less ofte n i n technica l writin g than in less forma l writing. K. Quotation marks are use d around direct quotations but not aroun d indirect quotations. I f the quotation extend s over more than one paragraph, quotation marks begin each paragrap h but end only the last paragraph. Quotatio n marks are used to set apart a word or phrase that is used in some sense other than the usually accepted one, bu t thi s i s easil y overdon e an d shoul d be avoide d a s muc h a s possible . Pu t commas an d period s insid e closin g quotatio n marks ; pu t semicolon s an d colon s outside. Othe r punctuatio n (questions marks and exclamation points) should be put inside the closin g quotatio n mark s only when the punctuation is actually part of the matter being quoted: H e asked: "Should th e catalyst b e added?" I s it really, a s written, "larger than the primary leaf? L. Hyphens are used : —i

n compoun d adjectives.

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-t

o form compound nouns , although it is often acceptable t o combine the two nouns into one word without the hyphen: mailman instead of mail-man, for example. — t o divid e word s a t th e en d o f th e line , but rule s fo r hyphenatio n are to o involved fo r summary here. Whe n in doubt, check in a good dictionary—o r trust you r word processor' s hyphenation feature. M. The slash is used in several technical applications, as noted elsewhere i n this booklet (e.g. , i n fractions : 1/20) . I t i s als o sometime s use d i n th e expressio n . ..and/or. . . in scientific writing. Som e editors do not like this and will suggest . . .or . . both. N. Underlining i s use d i n plac e o f italics i n type-writte n o r hand-writte n material. Ther e are instance s i n scientific writing where italics or underlinin g must be used , as i n scientifi c names o f organism s (se e Chapte r 2). Itali c typ e has bee n used appropriatel y in thi s appendi x to se t of f examples. Italic s can also b e used fo r emphasis, but thi s is discouraged i n technical writing. Foreig n words are underline d or italicized , especiall y if they are unfamiliar . 6. ABBREVIATIONS Science speaks its own language with specialized words that we must all learn in our respectiv e fields . Perhap s tha t i s why we always see m t o wan t t o inven t eve n more term s b y constructin g abbreviations . O f cours e man y abbreviation s o r acronyms are recognized; the y are already a part of the language of plant physiology: ATP, DNA , IAA, 2,4-D , NADP, SDP, and many more. Journal s often publis h list s of suc h accepte d abbreviation s an d expec t author s t o us e them . (Not e table s i n Chapter 10. ) Bu t i t i s an impositio n t o expec t a reade r t o lear n a handfu l o f new abbreviations in orde r t o rea d a paper. A few abbreviations (fou r o r five? ) ma y be justified to avoid the constant repetition o f some complex terms or phrases, but most authors will achieve a more sympatheti c audienc e i f new abbreviations are kep t t o a bare minimum . I t i s also helpful i f the newl y introduced abbreviations are easil y distinguished from eac h other. Consider , for example, a series o f treatments with or without auxin, light or dark, at morning, noon, or night: ALM, ALN, ALNi, NALN, NALN, NALNi, ADM, ADN, ADNi, NADM, NADN, an d NADNi. Pitt y the reader ! 7. UNNECESSAR Y WORDS We hav e a grea t tendenc y t o expan d ou r writin g b y using words tha t ar e no t needed or tha t hav e shorter an d more concise counterpart s (Heiche l et. al. , 1990). 1. Som e words can simpl y be droppe d (e.g. , simply i n thi s case) : prior histor y (all histor y is prior) careful study , careful examinatio n (how else would you d o it? ) very (thi s word only contributes something in certain negative constructions: It isn't very effective.) it i s shown that (seldo m needed) it i s a fact that (seldo m needed) it is emphasized that (seldo m needed) it is known that (seldo m needed)

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2. Som e word s ca n be replaced b y more descriptive an d concise terms : Instead of: Use: in th e absenc e of withou t higher i n comparison t o mor e than was found t o b e wa s in the even t tha t i f small number o f fe w was variable varie d additional added , more, or othe r approximately abou t at th e presen t tim e no w at tha t poin t i n time a t tha t time establish sho w identify find , name , or sho w in a timely manner promptl y necessitate caus e or nee d appears t o be seem s (als o overused , ofte n t o avoi d making a factual statement: I t seems to be raining. Better : I t i s raining.) 8. WORDS WITH SPECIAL PROBLEMS Some words are use d incorrectly so often i n scientific writing that some reader s may never lear n to use them correctly when they become authors. Som e of these ar e homonyms, which are pair s o r groups of words with identical or similar sounds bu t different spelling s an d meanings . Th e followin g list include s som e o f the proble m words includin g a fe w homonyms. Hopefully , th e lis t include s many of th e word s that pos e special problem s fo r speakers whos e native tongue i s not English . I f you are i n doub t abou t th e correc t meanin g an d spellin g of a word, check with a goo d dictionary o r i n a manual that list s such words (e.g., CBE Style Manual Committee , 1994; d e Mell o Vianna , 1977 ; Strun k and White, 1979) . accept, except Accept mean s t o receiv e o r admit , to regar d a s right or true , or t o bear u p under . Except mean s t o leave out , exclude, or excuse . affect, effect Eac h ca n be used either as a verb or as a noun, but mos t of the time , affect i s used as a verb (t o influenc e or caus e a change in) an d effec t i s used as a noun ( a resul t o r consequenc e o f an action). A s a noun, affect i s used onl y as a technical ter m i n psychology. Effect i s used as a verb in the sens e o f to cause (t o bring about or make). Technica l writer s like to soun d scientifi c by using effect a s a verb, bu t i t often lead s t o confusion , and i t i s easy to sa y cause instead. Eff as a verb sounds affected . Furthermore , affect i s a rather weak verb. I t i s better to tel l how somethin g i s affected: increased o r decreased, for example . as Whe n a s is a preposition, meanin g in the role , capacity, or functio n o f (see like, as below) , i t i s alway s followe d b y a nou n o r pronou n i n th e objectiv e case . Otherwise, th e cas e ca n depen d o n th e sens e tha t i s desired : Yo u need he r as much as I (i.e. , as much as I need her). Yo u need her as much as me (i.e. , as much as you need me). Ambiguit y can result when as i s used as a conjunction instea d

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of since o r because: Sh e did not hear the bell as she was on th e terrace. Di d sh e fail t o hea r th e bel l because sh e wa s on th e terrac e o r while sh e wa s o n th e terrace? as . ..as, s o . . . as I n positive comparisons , as...as is the construction tha t is used: a tough as nails. I n negative comparisons, eithe r as . . a.s or so . . . as can be used: ...no as (o r so) skilled a s his technician. Th e firs t as should not b e omitted in positiv e comparisons. (Don' t say : Th e sound wa s clear a s a bell. Say : ...as clear a s a bell.) can, may Ca n i s used t o indicat e abilit y to d o something ; may, to ask , grant , or deny permission t o d o it . Thi s distinctio n should be followed in formal writing. datum, data Traditionally , especially i n technical writing, datum ha s bee n consid ered singula r ( a fac t o r singl e ite m o f information ; a singl e number ) an d data plural, bu t popula r usag e ha s almos t eliminate d th e singula r datum fro m th e language, an d data i s almos t universall y used a s a singula r noun ( a collective : information organized for analysis). A few of us continue to say . . . thesedata are . but a s our generatio n die s off, data wil l no doubt be used only as a singular noun. (I fin d thi s regrettable! ) due to Thi s expression i s often overused in technical writing. I t is correct whe n it is used a s a predicat e adjectiv e that follow s som e for m o f th e ver b to b e an d i n the sens e o f caused b y or attributable to: Th e broken centrifuge wa s largely du e t o faulty maintenance. Thi s coul d b e replace d b y ...was caused largely by... I t i s somewhat les s correct , although commonly used, i n th e sens e o f because of , o n account of , owing to, o r through: Th e centrifuge failed du e t o faulty maintenance. In forma l writing , it would be better t o say . . .because o f faultyits, it's It s is the possesiv e for m o f the pronoun it, but used in this case without th e apostrophe: ...the graph with it s curves... It's i s a contraction o f i t is an d i t has: It's no t new; it's been done before. (Overus e of the contraction s sometimes makes the writing seem to o informal. ) et al. Thi s is properly use d in bibliographies t o mea n and others. Not e th e perio d after th e secon d element . Becaus e i t i s Latin , som e editor s insis t tha t i t b e italicized (o r underlined) . information I n som e language s othe r tha n English , th e comparabl e ter m fo r information ma y be a plural (e.g., French, Spanish, Russian) or may be used a s a plural (e.g. , German) . I t i s never correct i n scientific English to us e information as a plural: informations. lay, lie La y (t o put , place , o r prepare ) alway s take s a direct objec t (lay it down); that is, lay is a transitive verb. Li e (t o recline or be situated) never does; that is, lie is an intransitive verb. Bu t th e pas t tense and past participle of lay is laid, and the pas t tens e o f li e i s lay, the pas t participl e i s lain. Thi s certainl y leads t o confusion. Si t an d set are equall y troublesome. like, as Like an d a s are correctl y use d as prepositions expressing different senses . In this case, like indicates resemblance to the object mentioned: H e looks like his brother. I t ca n always be replaced b y similar to. A s indicate s a role, capacity , or function: H e serves as Department Head. (On e could say serves like a Department Head, referrin g to someone wh o is not a Department Head bu t serve s like one. )

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It is less desirable t o us e like as a conjunction t o introduc e a clause, althoug h i n formal writing this can be done i f the clause is an elliptical one in which the verb is not expressed : ...looks like a good day for science. Suc h a clause is not accept able in forma l writing if th e ver b i s expressed: ...looks like i t will b e a good day. In such a case, like must be replace d b y as, as if, o r as though: ...looks as if i t will be a good day. Fea r o f using like incorrectly ma y tempt a writer to us e as when like, used a s a preposition, is called for : Sh e acted like (not as) an idiot. may, might Originally , might was the pas t tens e o f may, bu t no w both verb s ar e used a s subjunctives expressin g possibilit y o r permissio n i n presen t an d futur e time. The y diffe r i n intensity rathe r tha n in time. I n the sense of either possibili ty or permission , ma y i s stronger tha n might: H e may go makes a stronge r cas e for hi s havin g permissio n t o g o o r th e likelihoo d tha t h e wil l go than doe s h e might go. (Se e can , may ; can is used t o expres s abilit y to d o something. ) medium, media Lik e datum/data, medium i s the singula r form o f media, but media is often use d as a singular collectiv e t o refer to the means of mass communicatio n taken a s a whole. I n careful writing, media as a subject should alway s be treate d as a plural , an d eac h individua l mean s o f mas s communicatio n shoul d b e expressed a s th e singula r medium: Television i s an influential medium. Together, television, radio, newspapers, an d periodicals make up the media. Scientifi c writers should b e carefu l t o distinguis h betwee n thes e tw o forms of the nou n when they are use d i n their origina l sens e of a surrounding or pervading substance i n which bodies exist or move: th e environment. A n object ca n only be surrounded by one medium, bu t differen t object s ca n be in different media. Bacteriologist s and plant pathologists ofte n incorrectl y us e media t o refe r t o a singl e sterilize d nutritiv e substance fo r cultivatin g bacteri a o r fungi . Medium i s also use d i n othe r sense s including tha t o f an intervenin g thin g through which a forc e act s o r a n effec t i s produced, o r a perso n throug h who m communication s com e fro m th e dead . Medium a s an adjectiv e als o refer s to somethin g intermediate, a middle state o r degree. nor No r is a conjunction used to express continuin g negation; often it is paired with neither: He was neither for the idea nor against it. She had no experience as a physiologist nor did the subject interest her. Th e word or can be used instead o f no r when th e elements are within a single independent clause , and it is clear tha t th e negative sens e carrie s ove r t o th e elemen t tha t i s introduced: H e was not for o r against the idea. She had no experience or interest in physiology. percent, percentage Percent (no longe r writte n per cent) i s specific and follow s a number or numeral: 1 8 percent. Percentage is nonspecific and should not b e used with a number : A small percentage died o n day three. (Us e a spac e betwee n a numeral an d th e percen t sign : 1 8 %. Se e Chapter 1.) precede, proceed Precede mean s t o com e befor e i n time , order , o r ran k o r t o introduce. Proceed mean s t o g o forward o r onward , to undertak e a n action . principal, principle Principal ha s severa l meaning s bot h a s a nou n an d a s a n adjective. A s a n adjective , it mean s leadin g or chief . A s a noun , it mean s th e leader or person i n charge or the capital or main body of an estate o r a sum owed

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as a debt: Th e principal o f th e school is my pal Principle i s used only as a nou n meaning a basic truth, rul e o f human conduct, o r fundamenta l law. proved, proven Bot h ar e pas t participle s o f th e ver b t o prove, bu t proved i s preferred: H e ha d proved his point. Proven i s more commo n when use d a s a n attributive adjectiv e befor e a noun: a proven record. I t is also the for m use d in the phrase not proven. (Becaus e o f variabilities cause d by chance, and because of possible alternativ e explanations , scientists mus t be wary of saying that something is proven. W e often striv e to disprove a hypothesis.) respectively Th e word means singl y in the orde r designated . I n scientific writing, it i s often quit e clea r tha t th e dat a presente d i n one brie f lis t ar e give n i n th e same orde r a s th e name s o r othe r informatio n i n anothe r list , an d th e wor d respectively insult s the intelligenc e o f the reader : Plants in the dark and in the light were etiolated an d green, respectively. Wit h few exceptions, i t i s best t o writ e th e sentence so that respectively i s not needed : Proline concentrations were 0.5 molL-1 for sample one, 1.32 mol.L-1 for sample two, and 3.56 mol.L-1 for sample three. Don't write : Proline concentrations were 0.5, 1.32, and 3.56 mol.L-1 for samples 1, 2 , an d 3 , respectively. Th e secon d wa y ma y be shorter , bu t i t i s inherentl y confusing. shall, will I n the mos t forma l writing, use of these words was governed by a series of comple x rule s tha t woul d b e understoo d b y few modern readers . I n moder n usage, both are used to indicate futurit y a s well as determination, compulsion , o r obligation, bu t will is becoming more common in construction of the future tens e (opposite o f the ol d rule) : Tomorrow, we will set up the experiment. Becaus e this can b e ambiguous , i t i s a goo d ide a t o us e som e othe r constructio n whe n determination i s the sense to be expressed: Tomorrow, we must (have to , certainly will) se t u p th e experiment. Shall is sometime s use d t o emphasiz e resolve : W e shall overcome. Bu t shall is slowly disappearing fro m th e language . since, becaus e Since is often used in the sens e of because, which is still a good use . Some editors , however , migh t insis t tha t it s us e b e restricte d t o th e followin g sense: ...the time that has elapsed since some event. so Whe n the conjunction so introduces a clause that gives the purpose of, or reason for, a n actio n state d earlier , it i s usually followed by that and no t precede d b y a comma: W e changed the solutions so that toxins would not build up . I n that usage, it is a subordinating conjunction. S o is used alone as a coordinating conjunction when th e claus e tha t i t introduce s state s a resul t or consequenc e o f something preceding: W e had t o finish, so w e worked late. so-called Thi s hyphenate d adjectiv e precede s a nou n tha t i s no t enclose d i n quotation marks : Th e dark period wa s interrupted b y a so-called night-break. Sometimes i t i s used sarcastically : ...a so-called leader. then, than Mos t commonly , then means at that time or refers to order o r position : First the seed germinates, then the seedling develops. Than i s used in comparisons: Cultivar A is more drought hardy than cultivar B. that, which , who , who m Se e th e discussio n i n Sectio n 3. A o n Restrictive an d Nonrestrictive Phrases and Clauses. That (o r wh o o r whom) shoul d be use d t o introduce restrictive phrases and clauses. Which, who, or whom (especially which),

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preceded b y a comma , are use d t o introduc e nonrestrictive phrases an d clauses. Who o r whom (dependin g o n case ) shoul d b e use d whe n th e referenc e i s t o people. Which i s alway s used whe n i t i s precede d b y that a s a demonstrativ e pronoun: W e often long for that which is impossible. thus, thusly Thus is always the choice. Bot h are adverbs, and thusly never need s t o be used . toward, towards Eithe r form i s acceptable, bu t toward i s most common in moder n writing (especiall y i n the Unite d States) . unique Somethin g unique is in a class by itself withou t an equal. A s an adjective, it is an absolute. Therefor e expression s o f comparison shoul d be avoided: most unique, rather unique, etc. Bu t some modifiers are acceptable an d logical: nearly unique, more (o r most) nearly unique. Th e same i s true o f such othe r absolutes as perfect or dead. were Were ca n b e use d a s the pas t subjunctiv e mood o f the ver b to be to expres s conditions tha t are clearly hypothetical or contrary to fact: I f i t were only possible. Such statement s ma y express a wish: / wish that the data were complete. Ofte n they ar e precede d b y if: I f ou r budget were only larger. Informally , was i s often used instea d o f were, and sometime s were i s incorrectl y use d instea d o f wa s i n indirect questions o r when the conditional statemen t is not really contrary to fact: ...if the report was true, changes would be necessary. They asked if he was agreeable. 9. SOME SUGGESTIONS ABOUT FORMAT AND WORD PROCESSORS

Most journals have printed instructions with many details on suitable format fo r manuscripts. Th e CBE Style Manual Committee (1994) als o ha s a n extensiv e discussion of format. Author s mus t carefully study such instructions before writing and certainl y befor e submitting a manuscript to a particular journal. I f the forma t does not follow that of the journal, reviewers may assume (sometimes correctly) that the manuscript was submitted to another journal and rejected. A t the very least, an incorrect forma t tells the editor that the authors were too careless to bother checking such details before submitting a manuscript—and thus may be careless in carrying out the scientific study that is being described. Incorrec t formatting also fails to consider the editors and reviewers who must read th e manuscript . A fe w suggestions, mostl y my own personal preferences , com e t o mind : Manu scripts submitte d fo r publicatio n shoul d always b e doubl e spaced ; thi s include s captions, footnotes , quotations , everything. Th e double spacing is to help reviewers, copy editors, an d compositors edi t an d otherwise mark the text . (Becaus e it is now so eas y t o reproduc e an d eve n t o rewor k a manuscript , it i s quit e i n orde r fo r reviewers t o writ e directl y o n th e manuscript. ) Title s shoul d b e bot h brie f an d descriptive. Becaus e th e titl e i s usually the firs t thin g a potentia l reade r sees , it s importance can' t b e overestimated. Nex t in importance is the abstract , which must also b e as brief as possible (s o as not t o discourage a potential reader) whil e at th e same tim e conveyin g all th e ke y point s includin g reason s fo r th e stud y an d th e important conclusions . Al l plan t materia l must b e accuratel y name d both i n th e abstract an d i n th e section s describin g method s an d material s (see Chapte r 2) . Figures an d table s conve y th e actua l dat a produce d b y th e stud y tha t i s bein g

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reported, s o i t i s extremel y importan t t o mak e the m a s complet e an d eas y t o understand a s possible. (Se e th e followin g section fo r many tip s tha t ca n appl y t o published paper s a s wel l a s t o ora l an d poste r presentations. ) I t i s a commo n practice t o us e different symbol s and lines fo r different treatment s shown in figure s and the n t o defin e thes e symbol s an d line s i n th e caption . Sometime s thi s i s necessary because there may not be room on the figure to label the curves, but if the curves ca n b e labelle d o n th e figure , i t become s muc h easie r fo r a reade r t o understand wha t i s bein g presented . Wh y shoul d a n autho r pla y game s wit h potential readers? Wh y should a reader have to learn a code to understand a figure? In an y case , th e captio n shoul d presen t enoug h informatio n t o mak e th e figur e understandable withou t having to rea d the text. Suc h details as dates an d statistica l treatments shoul d als o be included. The preparatio n o f manuscript s ha s bee n greatl y aide d b y word processing programs tha t reduc e th e tim e require d t o creat e an d especially t o revis e a manuscript and, most important, make it possible virtually to eliminate typographica l and other errors. Th e spell checker is especially valuable, and grammar checkers can also help, especiall y thos e authors whose native language is not English. Suc h programs are now used by almost everyon e world-wide, and many journals accept manuscripts in electroni c for m o n a disc . Nevertheless , ther e ar e a fe w minor problem s o r irritations tha t resul t fro m th e us e of word processing programs. There is a tendency to put too much faith i n the word processor an d not to proof the fina l manuscrip t before i t is submitted. Perhap s the mos t common errors aris e from editin g the manuscrip t on the compute r screen. On e makes a change but may forget t o remov e al l the materia l being replaced, for example. I t is still important t o carefully proof the final document. The word processor usuall y provides a capability not previously enjoyed by most authors: th e abilit y t o justif y th e righ t margi n (i.e. , alig n it, a s i n thi s book) . I t seems tha t fe w author s ar e abl e t o resis t th e temptatio n t o us e thi s capabilit y although i t sometime s produce s som e of those mino r irritations. Althoug h we are used t o reading type-set materia l with justified righ t margins, there are two reasons why "amateur" justification of the righ t margin is not alway s a good idea : First, man y authors ar e reluctan t t o hyphenat e (and it i s somewhat easier fo r a typesetter at the printin g press to work from a manuscript that has no hyphenation). The result with a justified righ t margin is that sometimes an exceptionally long word will not quit e fit at th e en d o f the lin e and is automatically moved (wrapped) by the word processor t o th e nex t line, leaving a large space that must be divided betwee n the words that remain i n the line . Thi s produces a line with a few words separate d by large spaces , lik e these , whic h can be distracting for a reader, wh o shoul d be abl e t o concentrat e o n th e conten t o f the paper . Wha t does righ t justification gain fo r the edito r an d th e reviewers ? I s understanding the pape r aided in any way by a justified right margin? Second, some printers (especially dot-matrix) are not capable of dividing the space left a t th e en d o f a lin e int o smal l fraction s o f a millimete r an d proportionin g it evenly among all the spaces between words and letters in the line. Instead , they work only with whole spaces (columns) , and thi s means that space s between some words

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are ofte n a t leas t on e spac e large r tha n space s betwee n othe r words . Thi s uneve n spacing occurs especiall y wit h non-proportional font s (e.g. , Courier). Som e reader s also fin d thi s distracting . If an author must justify th e right margin of a manuscript (and it can make a good initial impression) , grea t effor t shoul d b e expende d t o hyphenat e correctl y (a s professional typesetter s have always done), an d only the bes t o f printers capable of microjustification shoul d b e use d fo r th e fina l product . Otherwise , right-margin justification gains nothing while it provides an added irritation that may not produc e the desire d receptiv e attitude in a reviewer. 10. SUMMARY A. The sentence. 1. Tw o ideas in a sentence connected with a coordinating conjunction may share a commo n subjec t (o r sometime s a verb), in which case the y should not b e separated with a comma or other punctuation: Th e sentence presents one idea and adds another to fortify the first. 2. Independen t clause s connecte d b y a coordinatin g conjunctio n shoul d b e separated b y a comma before the conjunction : Th e first clause has a subject and verb, and the second clause also has both subject and verb. 3. Closel y related sentence s no t connected with a conjunction may be separated by a semicolon; thi s ties th e idea s together i n a special way (as here). Sep arating suc h sentence s wit h a comm a i s calle d a comma fault o r comma splice, th e habi t must be avoided. (Di d you notice th e example? ) 4. Les s relate d sentences are separated by periods. Thes e two sentences provide an example . 5. Whe n tw o ideas ar e relate d t o each other wit h a subordinating conjunction, they shoul d b e separate d b y a comm a i f th e subordinat e phras e o r claus e comes firs t i n th e sentenc e (when i s th e subordinatin g conjunction i n thi s case); otherwise, n o comm a is needed. 6. An d i t i s acceptable t o begin a sentence wit h a coordinating conjunction (as here; use d mor e a s a conjunctive adverb) althoug h this practice shoul d no t be overdone . B. Modifying words. 1. Compoun d adjective s ar e forme d b y connecting with a hyphen : tw o adjectives, an adjective and a noun, or tw o nouns: near-ultraviolet radiation, a tenwatt lamp, cell-wall structure. (Bu t omit the hyphe n with numerals followed by unit symbols: 10 0 W lamp.) 2. I n technica l writing , i t i s importan t t o us e adverbia l form s whe n a verb , adverb, o r adjectiv e i s being modified: a n unusually concentrated solution. 3. Noun s used as direct o r indirect objects or followin g preposition s ar e always in th e objectiv e case , which in English is only evident when expressed b y th e personal pronoun s me, him, her, us, them, and whom (o r whomever). 4. Althoug h some editors migh t disagree, authors would do well to use personal pronouns in writing technical articles for the scientific literature: W e homogenized th e tissue i n a buffer solution. Fo r on e thing , thi s avoid s us e o f th e

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D.

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Presenting Scientific Data

passive voice : Th e tissue was homogenized. . . . (Passiv e voice i s appropriate for Method s an d Material s sections. ) Modifying phrases and clauses. 1. A restrictive phras e or clause contains information that is essential t o understand som e par t o f th e sentenc e no t include d i n th e phras e o r clause ; a nonrestrictive phras e o r claus e add s informatio n tha t i s no t essentia l t o understand th e part s of the sentence no t include d in the phras e or clause . Nonrestrictive phrase s or clauses ar e se t apart by commas, but restrictiv e phrases o r clause s ar e not : Th e hypocotyl sections i n auxin solution curved down. Th e hypocotyl sections, in auxin solution, curved down. (Th e autho r determines th e restrictiveness. ) The relative pronoun that is used to introduce some restrictive phrases o r clauses; it is not precede d b y a comma: This was the sample that we examined. The relativ e pronou n which i s use d t o introduc e som e nonrestrictiv e phrases o r clauses ; i t i s precede d b y a comma : W e examined this sample, which [incidently ] nearly escaped us . Introductory o r fina l nonrestrictiv e phrases o r clause s ar e se t of f with a comma: I n preparation for th e experiment, w e collected th e necessary glassware. The relative pronoun who (or whom) is used with reference to people; that (or which) is used fo r everythin g else: Th e teacher wh o drew th e diagram. . . . The plant that grew. . .. Put tw o commas ( a pair), or none, between subject and verb, or verb and object o r subjec t complement : Th e hypocotyl sections, in gibberellin solution, curved upward. Not : Th e hypocotyl sections i n gibberellin solution, curved upward. 2. Parenthetica l phrase s o r clauses can be surrounded by commas, parentheses, brackets, or dashes. Th e choice i s up to the author. I f a phrase in parentheses comes a t the en d of a sentence, th e perio d goe s outside the parentheses . (Complete sentences initiated with the firs t wor d capitalized an d terminated with a period ca n also be include d in parentheses, lik e this.) Verbs. 1. Verb s mus t agree i n number (singular or plural ) with their subjects. 2. B e consisten t i n ver b tenses ; us e th e pas t tens e t o describ e method s an d results. 3. Us e the presen t an d past participle s correctly . 4. Wheneve r possibl e an d appropriate , us e th e activ e instea d o f th e passiv e voice. Further notes on punctuation. Thi s section contain s some rules not containe d in the previou s discussion , which also often concer n punctuation . Becaus e th e notes are alread y in a summary form, the y are no t repeate d i n this summary. Abbreviations. Avoi d using too man y ne w abbreviations. Unnecessary words. Tighte n you r writing b y dropping unnecessary words an d phrases an d b y using simple, concise form s wheneve r possible. Words with Special Problems. Chec k the lis t here or us e a good dictionary to use these words correctly.

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I. Suggestions about format and word processors. Chec k instruction s to author s published by the journal t o which a manuscript i s to be submitted. Watc h fo r errors tha t ten d t o appea r whe n on e use s a wor d processor ; proo f th e fina l printed manuscrip t carefully. Us e a high quality printer and avoid justifying th e right margi n unles s yo u us e a suitabl e proportiona l fon t an d us e prope r hyphenation a t th e en d of lines tha t require it. REFERENCES Anonymous. 1993 . Th e Chicag o Manua l of Style, Fourteenth Edition . Th e Universit y of Chicago Press, Chicag o and London , de Mello Vianna, Fernando. 1977 . Th e Written Word. Houghto n Mifflin Co. , Dictionary Division, Two Park Street , Boston , M A 0210 7 CBE Styl e Manual Committee . 1994 . Scientifi c styl e an d format : th e CB E manua l for authors , editors, an d publishers . 6t h edition . Cambridg e University Press, Cambridge , New York. [Se e also earlier edition s of CB E Styl e Manual.] Heichel, G.H. , D.E . Kissel , C.W . Stuber , G.A . Peterson , J.L . Hatfield , R.G . Hoeft , R.J . Wagenet , T.J. Logan , W.A . Anderson , an d W.R . Luellen . 1990 . Becom e a Mor e Successfu l Author . Journal o f the Soi l Science Societ y of America. 54[Sept-Oc t '90](5):iv-vii . Pinckert, Robert C . 1986 . Pinckert' s Practica l Grammar. Writer' s Diges t Books , 993 3 Alliance Road, Cincinnati , Ohio 4524 2 Strunk, William , Jr . an d E.B . White . 1979 . Th e Element s o f Style . Th e Macmilla n Company, Toronto. Man y writers say this i s still th e bes t guid e fo r goo d writing .

CONSULTANTS Ross E. Konin g Shirlen Eastern Connecticu t Stat e Universit y Uta Willimantic, Connecticu t Logan

e M. Pope, Emeritus Professo r h Stat e University , Utah

Andrea L . Peterso n Moyl Utah Stat e Universit y Uta Logan, Uta h Logan

e Q. Rice, Emeritu s Professo r h Stat e University , Utah

B STANDARDS FOR EFFECTIVE PRESENTATIONS Ross E . Koning Biology Departmen t Eastern Connecticu t Stat e University Willimantic, CT 06226-229 5 U.S.A . As scientists working in a rapidly advancing discipline, we must communicate effec tively a t regional , national , an d internationa l meetings . Whil e publication i s th e permanent record o f research progress , we rely heavily upon meetings presentation s to communicate our most recent ideas and results. Ther e are two common forms of meetings presentation : th e oral report an d th e poster. Thi s appendi x is primarily designed to assist with the preparation o f slides for the oral report, but much of the information applie s equally well to artwor k prepared fo r posters . To communicat e effectively , ora l presentation s mus t b e designe d t o optimall y deliver ideas and finding s within a timed interval (usually less than 15 minutes). T o achieve this, the artwork prepared for an oral report must be quite different fro m th e artwork prepared fo r publication. Slide s cannot have the finenes s o f detail nor th e complexity required of publication graphic s (for saving precious space in journals). Since an oral report lack s the luxury of long explanations and detailed study, each slide (o r viewgraph ) mus t hav e a simpl e format , mus t b e fre e o f nonessentia l information, mus t b e readil y understood, an d mus t hav e a single , clea r purpose . Each slide must be visible, legible, attractive, and integrated with the other slides and the oral presentation. I f properly designed, your graphics should catch the attentio n of the audience , reinforce your spoken ideas, and make your communication easier, faster, an d mor e exciting. Presentation plannin g software for computers may assist researchers i n designing effective graphics , but becaus e th e powe r t o desig n is still th e prerogativ e o f th e scientist, som e guidelines are needed t o us e this software t o best advantage. Man y examples of poorly designed slides generated by computer are evident at professional meetings. Thus , the guideline s presented here should be followed b y those who use computer graphic s facilities as well as those usin g older methods. Clearly, slides must not detract fro m th e presentation, so a key word for thinking about graphic s i s simplify! Yo u d o no t wan t you r audienc e t o wallo w i n th e particulars o f your approac h bu t t o understan d your result s an d t o com e t o your conclusions (literally to see what you mean). I t is important to keep methodological 188

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and statistica l detail s fro m cloudin g th e finding s o f your research . A n intereste d party ca n ask questions about method s an d analysis after you r presentation o r i n a private conference . You r finding s mus t stand abov e your process . The followin g sections present som e o f my ideas abou t presentations . 1. SLIDE PRESENTATIONS A, Planning your slides. T o kee p th e audienc e listenin g an d interested , yo u should organize and plan your presentation carefull y before any artwork is attempted . The process is essentially the construction of a storyboard. Again , computer software has proliferate d t o assist busines s worker s and (t o a lesser extent ) scientist s i n this process. First , compos e you r mai n messag e i n 2 0 word s o r less . Thi s shoul d constitute you r title. Assembl e a sequence o f similar short message s for each piec e of evidence leading to your conclusion. Desig n a graphic that will communicate each element o f th e evidenc e a t a glance. Thi s migh t be a graph , a photograph , o r a simple phrase. Allo w only one idea pe r graphic! Th e audience must both loo k an d listen, so it is critical to keep the slides and the spoken word simple and coordinated . To hel p organiz e you r presentation , a slid e o f you r question s o r mai n point s might be projected nea r th e start of the presentation. A s you progress throug h your presentation, th e outline slide could b e show n again with a topi c highlighte d i n a contrasting colo r t o conclud e th e correspondin g sectio n o r t o introduc e th e nex t point i n your presentation. A t th e en d of the presentation, th e lis t of questions o r main point s migh t be shown agai n with answers to reinforc e your summary. For complicated figures , use the build-up routine. Suppos e you wish to show the difference betwee n tw o curves sharing a common abscissa ( x axis). I n the firs t slide , the ordinat e an d absciss a ar e describe d an d th e firs t curv e is shown. I n the secon d slide, th e additiona l ordinat e i s adde d an d th e secon d curv e i s shown. (Th e firs t curve and its ordinate ma y remain o r may be drawn with thinner lines, or relegate d to a different colo r i n this slide.) I n the third slide, the area between the two curves is hatched t o emphasize th e differences. I n this way, three slides are used to presen t your findings. Now , to driv e the tren d home firmly , follo w u p with a text slide o f a phrase boldl y proclaimin g th e tren d (light stimulates shoot growth). Thi s fina l tex t graphic coupled wit h the build-up method makes your point clearly and memorably. Instead o f dryl y describing on e grap h with tw o lines o n a singl e slid e ove r a two minute period, yo u will spend perhap s 3 0 seconds o n each of four slides , each slid e having a clear purpose . I t helps your audience understand you better, an d you will have hel d thei r attentio n t o your presentation . Not al l graphic s i n your presentation nee d t o hol d information ; plain-color (no information) slides draw attention t o you and to important conclusions that you will simply state. Thi s incredibly valuable and effective techniqu e is seldom used but will really make your audience liste n t o what you are saying. Sinc e the previou s slide is replaced b y plain color o n the screen , th e audience is forced to hal t its examinatio n and t o liste n t o your interpretation . Your planne d presentatio n shoul d hav e enough slides t o preven t boredo m fo r your audience. Yo u shoul d plan to chang e slides at 3-5 slides per minut e (no mor e than 30 seconds spen t o n each slide). Limitin g each slide to one idea should assure

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that you have enough slides . I f you do not have enough slides planned to accommo date this change rate, then you probably hav e planned slide s that present more than one idea! Thes e need t o be simplified. Walkin g into a 15-minute presentatio n wit h five complicate d slide s assure s boredo m fo r your audienc e an d disrespec t fo r you . This is particularly tru e for weary audiences afte r a few days of a national meeting . On th e othe r hand , i f yo u alread y hav e 5 0 slide s fo r a 15-minut e presentation , adequate rehearsa l wil l hel p yo u decide i f you cannot presen t al l the slide s (ideas ) you may have planned. If , during rehearsal of your planned presentation, yo u cannot remember a particular poin t yo u want to make , you need anothe r graphi c elemen t that wil l remind yo u of what was important an d will help driv e this point hom e t o your audienc e a s well. Examine your presentation plan to be sure you have included title slides, question slides, evidence slides, and conclusion slides. Chec k carefull y t o not e whethe r you need duplicat e slide s fo r graphic s tha t ar e t o b e show n mor e tha n onc e i n you r presentation. Th e audienc e ha s no patience fo r you to give verbal instructions t o a projectionist t o tr y to locat e a previou s slid e i n a slid e tra y and the n t o retur n t o another specifi c slide t o continu e you r presentation . Never turn back! Th e story board mus t be unidirectional ! B. Preparing the artwork. Artwor k mus t be designe d t o a 2-height-by-3-width ratio, which convert s directl y t o th e 2 4 x 36-mm forma t o f the standar d slide . I t is best t o kee p th e artwor k awa y fro m th e edge s o f th e fram e an d t o hav e centra l weight to the figure . Colo r and lettering weight can be used to emphasize. Realiz e that wester n audience s wil l view the slid e from uppe r lef t t o lower right, so items in the uppe r righ t and lower left corner s o f the diagram are of less importance and may go unnoticed i n a complicated slide . Legibility i s a most-importan t criterion . Make it bold! Us e larg e fonts ! I f your artwork outpu t i s on 8. 5 x 11-inch or on A4 paper, tape it to a wall and stan d three meter s away . I f you ar e usin g a compute r scree n t o prepar e artwork , again move thre e meter s fro m th e scree n t o chec k fo r legibility . A t thi s distance , you r graphic ha s th e sam e visua l size a s a projectio n scree n viewe d fro m th e bac k o f a lecture room . Ca n yo u stil l rea d everything ? I s the poin t o f th e graphi c clearl y observed fro m thi s distance? I f not, then the lettering fonts , symbols, line thickness , or other elements o f the artwor k must be made larger or bolder . As a fina l chec k fo r legibility , hold th e graphi c that ha s been converte d t o a 2 x 2-inch slid e 4 0 cm fro m you r nose. Chec k t o b e sur e you can read everythin g and that th e poin t o f th e graphi c i s clearl y observed fro m thi s distance . I f not , the n either th e letterin g o n th e artwor k must be proportionally large r o r the slid e mus t be retake n t o mor e nearl y fill th e frame . Legibility i s assured i f a fe w simple rule s ar e applie d t o al l graphic s use d i n a n oral presentation . A Koda k publicatio n (Koda k #2 , 1986 ) i s a goo d technica l discussion o f legibilit y parameter s an d give s excellen t tip s fo r makin g your slide s readable. Text. Eac h textua l graphic should be limite d to a fe w (less tha n 10 ) words. A text slid e shoul d b e though t of a s a n idea-gram . I t make s your poin t dramatically and remind s yo u o f wha t t o sa y withou t havin g note s t o handl e (o r shuffle!) .

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Complete sentence s are seldo m legibl e o n a screen, so you should never hav e much to rea d o n a slide . I f you read a slid e t o th e audience , yo u will bor e them ; i f th e audience read s a slid e while you discus s it , the y are no t listenin g carefully t o you . Helvetica o r other sans-seri f typefaces (suc h a s thi s one) ar e much more readabl e in graphics tha n serif-fonts such as Times Roma n (lik e this) . Th e font siz e must be tall enoug h s o tha t onl y 1 2 lines would fil l th e slid e area fro m to p t o bottom , an d wide enoug h s o tha t onl y 36 characters woul d fill th e slid e are a fro m lef t t o right . The fonts must be bold; the thickness of the lines used to form each character shoul d be betwee n 1/1 0 t o 1/ 5 of th e heigh t o f th e character . I f these siz e guidelines ar e followed strictly , then everyone, eve n those in the back of the conference room , will be able to see what you intend t o show them. Thes e legibility rules appl y equally to lettering on tables, graphs, an d other artwork. Tables. Prepar e a slide showing onfy th e portion of the tabl e tha t you intend t o discuss; leav e ou t unuse d data . Excessiv e ra w dat a an d particularl y unprocesse d statistical table s ar e roadblock s betwee n yo u an d your audience ; you r audienc e i s likely t o b e mor e intereste d i n plan t physiolog y than i n statistica l analysis . I f you plan t o focu s onl y o n a fe w cell s i n you r table , the n reformulat e th e tabl e fo r projection. Reserv e the complet e tabl e as a photocopy for private discussions with interested conferees . Alternatively , reserv e th e complet e table as an informational slide afte r you r fina l slid e a s potentiall y usefu l i n answerin g a questio n fro m th e audience. Moreover , i f you wish to reac h a large r audience, a handou t migh t b e desirable. However , i f you do have a handout, pass it out onl y when the tal k is over, so the audienc e will be listening and not readin g during your presentation. B e sure your name, address , an d phone numbe r are printed on the handout so a member of the audienc e ma y contact yo u later fo r discussion. In any case, table s for your oral presentation shoul d have no more than fiv e rows or columns t o sta y within the limits of legibility and sensibility. I t is better t o divide a large table into smaller portions o n several slides than to present an illegible smear of tiny digits for several minutes . I t is important to note tha t graphs (line, bar, pie) are usuall y far mor e illustrativ e an d memorabl e than number s in tables . Line graphs should be bold an d legible. Man y computer graphics programs draw axis and plotted line s to o finel y b y default an d need t o be modifie d fo r making bold projection slides . Ther e should be no more than eight marked ticks on any axis, and all lettering shoul d conform to the legibilit y rules for text (above). Again , computer programs usuall y default t o smal l font s suitable fo r publicatio n but unsuitabl e fo r projection. Ideally , you should show only one or tw o lines or curve s on each slide , but you may build up to a multiple-curve figure by revealing a new line on successiv e slides. Bar graphs should hav e no more than eight bars and, if stacked bars are used, the bars ma y be (shoul d be ) reveale d sequentiall y or i n group s by color o r textur e fo r contrast. Pie charts shoul d hav e fewe r tha n 1 0 slices . Colo r o r textur e contras t an d "pulled-out" slices ca n b e employe d fo r emphasis . Sequentia l emphasis in a slide series ma y better communicat e your findings.

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Colors can be used t o great advantage , but th e overuse o f colors i s only distracting. Th e ease of applying color i n computer-generated graphic s tempt s researcher s to us e too man y colors. Wheneve r possible, associat e a color wit h a particular typ e of information. Th e color s mus t contrast wel l in order t o b e distinguished. Ligh t colors on a dark background are very legible. Dar k colors on a medium background are seldo m appreciated . Extrem e contrast i s needed fo r partially-darkene d lectur e halls, bu t i n fully-darkene d room s extrem e contras t fatigue s th e visio n o f you r audience. Hig h contras t blac k and white positives and negatives will be more easily appreciated i f dye d t o a paste l color . Thi s take s th e "edge " of f o f th e excessiv e contrast. Thi s i s particularly important if you intend to mix black-and-white artwork with typical color slide s or othe r continuous-tone artwork . Do no t underestimat e th e specia l connotation s o r emotiona l impac t o f certai n colors (Xerox , 1985) : Red: stop , danger , fire , anger , warmth, passion, excitemen t Blue: police , navy, sea, serenity , sky, fidelity, water, coolnes s Green: go , growth , trees , country , spring , restfulness , youth , freshness , money (USA ) Yellow: caution , sunlight , cheerfulness, heat, light, life White: hospitals , sterility , purity , innocence, peace , calm Gray: somberness , dignity , quietness, age, wisdom, gravity C. Making the slides. A variety of techniques can be employed to conver t welldesigned legibl e ar t wor k t o effectiv e slides . Scientist s wit h acces s t o compute r graphics equipment can generate slides directly from their computers. Severa l highly sophisticated program s are now on the market to create beautiful, multicolored slides (e.g., Harvard Graphics , Power Point , Slid e Write, WordPerfect Presentations, etc.) . It is possible t o photograph thes e directly from th e screen although resolution i s not as good a s when th e compute r fil e fo r the slid e i s sent t o a fil m recorde r designe d to expos e th e fil m accordin g t o th e file . Suc h recorder s cos t a t leas t a thousan d dollars (althoug h price s hav e been droppin g sinc e the y first cam e o n th e market) . If yo u don' t hav e th e recorder , yo u ca n generat e th e presentatio n graphic s o n diskettes tha t ar e the n sen t t o agencie s t o b e converte d to slide s (a t cost s around $5.00 pe r slide. ) If th e compute r facilitie s are no t availabl e to you , or i f you haven't tim e t o g o through the sometimes involve d process of using computer programs to produce th e slides, yo u can use th e tried-and-tru e photographi c processes tha t everyone ha d t o use before th e compute r revolution . Basically , these processe s involv e puttin g th e graphs, tables , words , o r othe r material s o n pape r o r othe r suitabl e mediu m an d photographing th e result s t o mak e slides . Suc h slide s ca n b e draw n b y hand o r produced wit h suitabl e softwar e on a computer attache d t o a high-qualit y printer. Often, th e Universit y or othe r organizatio n ha s a photography laboratory tha t will make th e slide s fro m th e ar t work . Som e workers lik e to o r mus t go through th e entire proces s themselves , usin g technique s describe d i n th e appendi x t o thi s appendix. One quic k and simpl e approach is to photograp h the ar t work , on a goo d copy stand, usin g color slid e fil m (direc t positive). Thi s give s fairl y satisfactor y result s

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even wit h black-and-white copy, providing that you remember to over expose b y 1/2 to one full f stop s o tha t th e backgroun d wil l appea r brigh t instea d o f gre y whe n projected. O f course , i f you us e color film , yo u can add colo r t o th e ar t wor k o r even us e color filters when makin g the slides . H. Showing the slides. Ther e is no replacemen t fo r adequate rehearsal o f your slide presentation . I t wil l show errors i n you r planning, errors i n logic , error s i n legibility, an d certainl y hel p you fee l mor e confiden t when you actually deliver th e oral report at the conference. O f course, this rehearsal must begin sufficiently befor e the conferenc e s o that error s ca n be corrected. Yo u should begi n t o prepare you r oral report a s soon a s possible. During rehearsa l b e sur e you r slide s ar e i n mount s tha t wil l functio n i n th e standard Koda k Carousel 14 0 tray. Thi n plastic mounts jam less frequently tha n any other type. Th e mount s should b e numbered so that if a stack of slides is dropped, order ca n be quickly restored. Yo u should place a dot or an x in the proper corne r of th e moun t s o tha t i t will be oriente d properl y at th e conference . Th e standard convention fo r placement o f this mark is to hol d the moun t so that th e slide can be properly read and to mark the lower left corne r of the mount. Th e projectionist will then reorien t th e moun t so the mark is in the upper right corner. Thi s inversio n of the slid e will assure prope r orientation o n th e screen. B e sure to check this orientation o f your mark during rehearsal! When yo u trave l t o th e conference , carr y your slides i n a carry-o n bag to avoid loss wit h your checke d baggage . I f your rehearsa l ha s bee n adequate , yo u shoul d arrive, slide s i n hand , a t th e conferenc e confiden t tha t you r presentatio n wil l b e organized, legible , an d understandable. At th e sessio n fo r your presentation , arriv e before the beginnin g of the sessio n to presen t you r (marke d an d ordered ) slide s t o th e projectionis t an d familiarize yourself with the roo m an d its facilities. Brin g photocopies and maybe an overhea d transparency o f eac h graphi c just i n cas e th e slid e projecto r fails . I f the projecto r lamp burns out, you r 15-minut e time slot i s too shor t t o have the lamp replaced i n time for you to finis h wit h slides . When i t i s your turn to speak , remember never read a prepared speech. Ther e is no more boring method o f delivery, and your audience unconsciously wonders if you did the work you are presenting. "I f you did the work, then why must you read about it?" Yo u shoul d b e abl e t o discus s the artwor k without a written text. Moreover , many auditori a ar e no t equippe d wit h readin g lights . Le t you r artwor k be your notes. Never read a slide t o th e audience! Th e onl y thin g worse tha n projecte d sentences i s projected paragraphs . You r audience thinks, "Why give an oral presen tation; jus t publis h th e work! " Grammaticall y correct sentence s wit h complicate d logic and suitably condensed fo r journal publication are incomprehensible in an oral presentation; us e simple, direct, conversationa l English . Be careful in your use of a pointer, especiall y a light pointer (e.g. , a laser pointe r that project s a smal l red dot). I t i s very distracting to a n audienc e when the ligh t from the pointe r dance s or wave s around excessivel y on the scree n and especiall y when it dances all over the room while you are talking but not pointing. Hol d it still or mov e i t slowl y to emphasiz e what yo u want , an d turn i t of f when i t i s not being used!

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I. Special language problems. Yo u fac e a n especiall y difficul t challeng e i f you must giv e your presentatio n i n a language tha t i s not your nativ e tongue . Englis h has become the international languag e for scientific presentations, an d most scientist s everywhere no w rea d an d ofte n spea k English . Man y scientist s whos e nativ e language i s not English , however , d o not fee l confiden t enoug h i n the languag e t o give an oral presentation withou t a written text, which breaks the rule just presente d to never read a prepared speech. I n spite o f this rule, it is common a t internationa l meetings t o hea r presentation s tha t ar e rea d i n Englis h b y non-English-speakin g scientists. Th e fac t tha t th e talk i s read instea d o f being presented spontaneousl y is already enough to lose the interest of many if not most in the audience, bu t often the speaker i s not highl y proficient in English, so that his or her unfamilia r accen t add s still another solid barrie r betwee n th e speaker an d the audience. Ther e are severa l options availabl e t o you if you must present a talk in a language in which you are no t highly competent. Th e following two options depen d on the status of your presentation: i. You arrive at the meeting with a conventional manuscript, perhaps one that has not even been edited by an English-speaking editor. Yo u shoul d strongl y consider askin g a fello w scientis t whos e nativ e languag e i s Englis h (o r th e language o f th e conference ) t o rea d th e pape r fo r you. I f you do , thi s perso n should have time to study the manuscript before presenting it , making grammatical and stylistic suggestions tha t will improve understanding. Th e reader shoul d practice reading th e manuscrip t and be admonished to read slowly with frequent pauses, eve n insertin g spontaneou s remark s tha t hel p t o clarif y wha t i s bein g presented. Remember , however , tha t no t al l scientist s whos e nativ e tongu e i s English ar e skillful reader s wh o can read smoothl y without backing up to correc t small errors. I f there is time, the frien d migh t even study the manuscript until he or she has become s o familiar with its contents tha t he or she can use your slides to presen t th e materia l withou t readin g it . Remember , yo u will b e ther e t o interrupt th e perso n wh o i s givin g your talk ; you ca n correc t an y mistake s o r misconceptions—and yo u wil l b e th e on e wh o answer s question s durin g th e discussion period. B y having someone familiar with the language read your paper, you will almost certainl y communicat e with the audienc e better tha n if you read the pape r yourself. ii. You have time before going to the meeting to follow the suggestions that are presented in this section but still feel that you must read the paper. Remembe r that a n ora l presentatio n differ s i n significan t ways fro m a publishe d technica l paper. Man y of thos e who mus t present thei r tal k in a foreign language simply read a manuscrip t tha t ha s bee n prepare d exactl y a s i f i t wer e goin g t o b e published—as often it will be. Suc h a format i s especially difficult fo r an audienc e to follow. Instea d o f using this rather standar d procedure, outlin e your talk as a series o f logically related, simpl e ideas, and prepare at least one slid e for each of those ideas , a s discusse d above . The n write , probably in your ow n languag e t o begin wit h s o tha t idea s will flo w freely , a shor t paragrap h that describe s eac h slide. Havin g done this, you can then either practice the English version until you are proficient—possibl y s o proficien t tha t yo u won't hav e to rea d i t afte r all—o r

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you can persuade a n English-speaking fello w scientist to read th e paragraphs for you. Yo u migh t eve n hav e tim e t o sen d you r slide-relate d manuscrip t t o th e friend befor e th e meetin g s o that h e or she can practice reading it. I n any case, preparation base d upo n idea s an d slide s rathe r tha n the usua l technical-manu script forma t will lead t o muc h better communicatio n with your audience . 2. POSTER PRESENTATIONS Part o f th e cultur e o f moder n plan t scienc e i s tha t mos t presentation s a t professional meeting s are now in the form of posters. Th e poster session consist s of two distinct parts: th e physical poster an d informal discussions of the research wor k presented o n the poster. Researcher s prepare th e physical poster at home but must also b e prepared fo r the discussion s to tak e place at th e meeting. A. The Physical Poster. Eac h society has specifications for their poster sessions , and these are usually found in the brochures calling for abstracts to be submitted for the meeting. Th e specifications provide the scientist with dimensions and orientation for th e display boards. Th e entire poster mus t be prepared with th e size and orientation i n mind. A four-foot-squar e poster (commo n i n th e U.S. ; a littl e ove r a squar e meter ) mounted wit h the to p o r center nea r eye-leve l i s simple to prepare. Th e title goe s at th e top , an d graphi c element s place d virtuall y anywhere on th e boar d wil l b e visible at a glance. I n general, a Western viewe r will examine a poster fro m lef t t o right an d fro m to p t o bottom , s o th e element s ar e usuall y arrange d t o match . Contorted path s t o follo w th e element s should be avoided. If th e specification s ar e fo r a 4x8-foo t rectangl e (o r comparabl e metri c dimensions), the preparations mus t be more careful. I f the orientation is horizontal at eye level, th e autho r mus t prepar e th e poste r wit h the ide a tha t th e viewe r will work across th e poste r fro m left-to-right . Moreover , wit h th e genera l left-to-righ t movement o f session participant s throug h the poste r displays , it will be difficul t fo r discussants t o hav e to mov e back to th e lef t fo r a second ro w of graphic elements . Some meeting s avoi d thi s movemen t proble m wit h 4x8-foo t board s standin g vertically. Th e reade r wil l work down a poste r wit h thi s orientation , bu t graphi c elements place d abov e 6-fee t fro m th e floo r o r belo w waist-height are difficul t t o observe. Thes e area s shoul d b e restricte d t o ancillar y element s suc h a s larg e photographs no t needin g muc h close examination . Th e essentia l element s o f such a poste r shoul d b e placed i n a 4x4-foot square centered a t ey e level. Bold, sans-serif fonts (like this) are preferred for all text. Fanc y or calligraphic fonts shoul d be avoide d because o f inherent poo r legibility. Th e title of the poste r should be lettered a t 90-point o r larger type. Th e title should state the major point or findin g o f th e researc h clearl y and i n a s fe w words a s possible . I n genera l i t should match the titl e found i n the published abstract and program booklet fo r th e meeting. Nearby , the author(s ) names and universit y or researc h organizatio n and location shoul d appea r i n moderate-size d typ e (perhap s 60-point) . Th e majo r headings o f th e poste r design should also be in 60-point type. Th e bulk of any text elements should be i n 30-point type or larger.

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The poste r i s no t a "journa l article o n a board, " and lon g passages o f tex t ar e completely inappropriat e fo r a poster session . Instead , the text elements shoul d be largely idea-grams that lea d th e viewe r through the othe r graphi c elements to th e conclusions draw n from th e research . Th e sequence of presentation ma y be similar to a journal article, however . A cop y o f the poste r abstrac t migh t be the firs t graphi c element afte r th e title . The abstract puts the entire research body into a concise paragraph that a viewer can read to determine whether she or he wishes to continue to examine the poster o r go on to something else . Thi s migh t be the longest tex t element o n the poster . A brie f introductio n presentin g th e backgroun d o f th e researc h an d perhap s introducing the particula r organis m studied might come next . Thi s should b e very brief and cover onl y the essentials . Thre e o r fou r sentence s woul d be a good guideline. A photograph coul d b e appropriate here . Unless th e researc h detail s th e developmen t o f a ne w procedure, a n effectiv e poster migh t simply include a flow chart rather than a long text explaining methods. In many cases a photograph or drawing communicates what would take many words to explain in text . Most o f th e graphi c elements o n a poste r presen t th e researc h results . Thes e graphic element s consis t o f photographs , graphs , tables , autoradiograms , etc . Effective poster s frequentl y hav e simpl e figur e caption s o r title s declarin g th e interpretation draw n fro m eac h accompanyin g graphi c element . Eac h graphi c element shoul d b e larg e an d bold . Th e boundin g rectangle for graph s and chart s might be 2 0 x 30 cm. Th e minimu m type size should be 30-poin t for al l lettering. Graph symbols should approach 6 mm in width, and connecting lines should be 2 to 4 m m wide . Th e graphi c element s ca n b e slightl y mor e comple x tha n thos e presented i n slide s fo r ora l presentations , bu t n o mor e tha n thre e line s shoul d normally appea r o n a grap h (unles s th e figur e present s a famil y o f closely relate d curves), and bar charts should be limited to fewer tha n 10 bars. Eac h element should have a brief explanatory caption, bu t lon g passages are best avoided . There i s n o discussio n sectio n o n a poster . Neve r wast e preciou s spac e o n discussion tex t elements . Th e purpos e of a poste r sessio n i s to personall y discuss your researc h wit h intereste d viewers . Thi s interactio n betwee n scientist s i s th e beauty of the poster session . Th e verbal discussions cover the details of the researc h and suggestions for improvements, etc. You r poster should provide the evidence and support for the verbal discussion. O f course, the main conclusions will appear in the abstract. Thi s i s important because som e viewers will stud y your poste r when you are no t availabl e for discussion. The las t graphi c elemen t i n th e poste r sequenc e should b e a summar y o f th e research findings . A bulleted lis t i s sometimes effective; a concludin g mechanistic model diagra m might be more memorable . Very fe w viewers ar e prepare d t o writ e down a lis t o f references t o tak e hom e with them , s o a literature-cite d sectio n i s generall y a wast e o f poste r space . Established scientist s wil l kno w th e fundamenta l literature , an d a n intereste d newcomer will write to you after th e meetin g for references an d reprints. Havin g a business card with you migh t b e a hand y and considerate alternative.

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Some scientist s brin g summarizin g handouts wit h the m t o giv e t o intereste d parties. Whil e thes e coul d b e a s formal a s an articl e reprint , the y are generall y a "miniature" poster wit h a few literature references. I t is difficult t o judge how many copies o f a handout t o brin g with you. B. Setting up the poster. Ther e ar e man y style s o f poste r graphi c elements . Careful us e o f colo r i s effective ; excessiv e us e o f colo r i s distracting . To o man y graphic element s ar e intimidatin g an d stifl e discussion . Man y peopl e brin g th e individual poster elements an d their captions, etc. on individual cards or sheets, often on 8.5x11 or A4 sheets. Thes e hav e to be mounted on the display boards individually; spacing and alignment must be adjusted at the meeting. Thi s takes time that you might choose to spen d i n oral session s o r otherwise. A better pla n is to attach th e poster element s ont o large r cardboard s wit h spacin g and alignmen t determined a t home. Thu s th e assembly of the poster a t the meeting involves only putting a small number of cardboards together . O f course, th e smaller sheets ma y be easier t o pack in your briefcas e o r suitcase . C. The poster discussion. A t the prescribe d time , the author(s ) are t o stand a t the poste r an d discuss th e researc h wit h interested viewers. Thi s is the opportunity to shar e ideas , t o commen t o n technique s an d interpretations , t o improv e th e science, an d sometimes t o make new friends. Th e author should not approach eac h passer-by an d launch int o a dee p presentation . Instead , the autho r let s th e viewer initiate a discussion . Th e viewe r usuall y is allowe d t o lea d th e discussio n i n a particular direction . O n th e othe r hand , occasionally a viewer will simply ask th e author to "present " th e research. The n th e author is free to launch into a discussion in his/he r ow n direction. Man y viewers will simply want to examine the poste r an d draw their ow n unspoken conclusion s withou t discussion.

Appendix to Appendix A Photographic Techniques for Creating Slides For thos e wh o lac k compute r photographi c facilitie s o r budget s fo r outsid e consultants, Kodak' s pamphle t # 3 (1987 ) an d it s addition s (Koda k #4 , 198 2 an d Kodak #5 , 1982 ) ar e helpfu l a s a n overvie w of th e proces s o f makin g your own lecture slide s with simple and relatively inexpensive photographic techniques. The y present som e o f th e option s availabl e t o mak e reasonable slide s fo r presentation . Another Koda k pamphlet (Koda k #6,1985) is an excellent how-to booklet for several methods o f producing text slides. A small poster (Koda k #7,1987) review s film s (and thei r availabilit y an d processing) , thei r uses , an d technique s fo r particula r applications (text , charts, line drawings, prints, electron micrographs, chromatograms, electrophoresis gels , autoradiograms, gross specimens , and lab scenes) . Your artwor k wil l likel y fal l int o tw o categories : continuou s ton e an d hig h contrast. Continuous tone artwork consists of images containing various shades of gray or various colors. Thes e ar e best rendered int o slides by photography with continuous tone black-and-whit e (e.g., Koda k Rapid Proces s Cop y Film o r reverse-processe d Technical Pa n Film ) o r colo r slid e fil m (e.g. , Ektachrom e or Kodachrome).

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High contrast artwork consists of images containing only black and white or vastly different shade s o f color. Thes e are bes t rendere d int o slide s b y photography with high-contrast black-and-whit e film s [e.g. , Dektol-processed Kodalith , Technical Pan , or Precisio n Lin e (LPD4 ) films ] o r high-contras t colo r fil m [Vericolo r Slid e Fil m (SO-279)]. Kodalith , Technica l Pan , and Vericolo r film s produc e a "negative" slide of th e artwork . Th e dar k lines o n th e artwor k are clear o n the slid e an d the whit e background of the artwork will be intensely black (black-and-white films) or intensely colored (colo r determine d b y filte r selectio n wit h th e Vericolo r film) . Koda k Precision Lin e fil m produce s a positive imag e (intensely blac k line s o n clea r back ground). A s mentioned previously , high-contrast black-and-clea r slides fatigu e the vision o f your audience i n fully darkene d room s and should be dyed so that the clea r areas tak e o n a light paste l shad e t o reduce contrast . D. Methods for continuous tone slides. Koda k Technical Pa n Fil m 241 5 i s a n incredibly fine-graine d negativ e fil m tha t ca n b e processe d t o variou s degree s o f contrast (Koda k #8 , 1982) . I t therefor e make s a universa l fil m fo r al l sort s o f applications. Wit h a POTA developer [1. 5 g l-phenyl-3-pyrazolidinone (i.e., Phenodone), 3 0 g sodium sulfit e pe r lite r distille d wate r use d fo r 1 5 min a t 2 0 ° C wit h agitation], norma l contras t blac k and white negative s ca n be mad e fo r printin g o n photographic paper . Norma l contrast blac k and white slides can be made by reversal processing a s describe d i n th e bo x a t th e en d o f thi s appendix . Extremel y high contrast negative s fo r reversed-tex t slide s o r publicatio n print s ca n b e mad e b y exposing th e fil m a t AS A 20 0 (1/3 0 s a t f/1 1 usin g 4 15 0 W photofloods ) an d developing th e fil m i n undilute d Dekto l fo r 2 min a t 2 0 ° C wit h continuous slo w agitation. Whil e th e reversa l processin g coul d b e use d t o mak e high-contrast , normal-text slides , LPD 4 i s a more convenien t alternative . As note d above , colo r transparenc y film s (Ektachrome , Kodachrome , an d equivalent) ca n be used t o make slides from artwork . Colo r reproductio n can be an advantage t o distinguis h portion s o f pie charts , bars i n histograms, etc. However , standard blac k an d white artwor k loses some contras t with these films an d appear s dark gra y o n ver y ligh t gra y background . Moreover , an y corrections an d surfac e irregularities i n the artwor k will be visible in the fina l slid e because o f the low-con trast colo r rendition . Color transparency film s ar e very useful fo r showing the plan t used, the method s and equipmen t employed , an d your colleagues fo r the study, but tables , graphs , and line drawing s from you r data ar e bette r presente d i n slides o f higher contrast . E. Methods for high contrast slides. Th e best quality high-contrast negatives ar e prepared fro m Kodalit h (o r similar ) graphi c art s film s processe d i n an y o f th e Kodalith or similar (undilute d Dektol) developers. Thes e materials give an intensely black background with very clear line-images . Th e film i s insensitive t o red safelight and, therefore, als o to red or other faint-color guidelines on your artwork. Sinc e th e contrast o f the fil m i s so high, corrections t o artwork made by clean erasure , white out ink , an d clea n correctio n tap e ar e invisible . An y undesirable mark s tha t d o appear ca n be blotte d ou t o n th e negativ e with a n opaque ink (e.g. , fro m a perma nent-black marking pen) or special opaquing material available in photo stores. Th e negative ca n b e printe d t o mak e publication print s or i t ca n be mounted i n a slide

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mount for projection a s a reversed-text slide . A s a slide, the extreme contrast tempts one t o dy e the fil m prio r t o mounting . Thi s is especially tru e when projection i s to be in a small, completel y darkene d room . However , i n large auditoria wit h incom pletely drape d window s or "hous e lights" , the extrem e contras t i s highly desirable . The very popular blu e backgroun d slides ar e made with SO-279 Vericolo r Slid e Film (Koda k Pamphle t E-24) . Thi s i s exposed fo r 6 seconds a t f/1 6 through a n O (range) "G " filter t o artwor k illuminate d by 2 x 500 W Photofloods held 1 m away from an d a t a 45° angl e t o th e artwork . Th e fil m i s processed fo r 5 min at 3 5 ° C in Unicolor K 2 Chemistry (or equivalent C-41 processing). I f you do not want to do color photographi c processing , yo u ca n tak e th e expose d fil m t o a "One-Hou r Photofinishing" company and ask for negatives only. Thes e ca n then be mounted i n Pakon (o r equivalent thin-plastic ) slide mounts. (Th e company might do the mounting.) In a pinch , you ma y substitute Kodacolo r I I (o r equivalent ) for SO-279 , expos e it after metering a t the manufacturer-recommende d ASA, and have it processed fo r negatives only . Th e background colors will be weaker and the printe d areas wil l be slightly orange . LPD4 Kodak Precision Lin e Film is a direct-to-positive film for making black-line slides fro m black-lin e artwork. Th e fil m i s exposed fo r 1 0 s at f/9. 5 using 2 x 500 W Photofloods a t 45 ° an d 8 0 cm from cop y center. I t is developed 1 min in undiluted Dektol at 20 °C with slow continuous agitation. Fix , wash, and dry as any other film . The brilliant clea r backgroun d and crisp black lines of these slides mak e them suitable fo r us e i n a larg e auditorium , fo r us e i n wea k projectors , an d fo r us e i n inadequately darkene d rooms . Thes e slides are excellent i n any projection environment. A disadvantage i s observed whe n these slide s are projected i n sequence wit h color slide s o r other less-brilliant slides . Th e contrast ca n be painfully excessive ! I f this is anticipated, th e backgroun d can be dyed to reduce contrast. I t is undesirable to reduc e contras t ver y much, so very dilute solution s o f water-soluble dyes should be used to obtain weak staining of the protein emulsio n (Frost, T.M . and P.A. Jones , 1982). F. Adding color to black-and-white slides. Negative s and slide s from black-andwhite film s ma y be dye d i n dilut e solution s o f water-soluble dyes. I sugges t one percent o r more-dilut e solution s of Tartrazine Yellow, Acid Orang e II , or Naptho l Green. Addin g glacial aceti c aci d t o mak e the dy e solution 0. 5 % aceti c aci d will improve th e uniformit y of th e staining . A brie f rins e i n wate r afte r stainin g will prevent formatio n of opaque dy e crystals on th e fil m (Homer , J.A . an d C . Pennington, 1974) . Individual line s o f typ e ca n b e emphasized , particularl y o n black-and-whit e reversed-text negatives , by highlighting them with water-soluble ink from fel t markers (e.g., Vis a Vis ) designed for overhea d projection . I f the marks are mad e on th e shiny (backing ) sid e o f th e film , the y ca n b e washe d of f easil y an d reapplie d a s needed. G. Recovering from disasters. Farmers Reducer i s an amazin g treatmen t that can eliminat e the exces s silve r in th e region s of a black-and-white slide or negative intended t o b e clear . A n overexpose d o r overdevelope d negativ e slid e ca n b e

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corrected by cutting silver from the film. Farmer s Reducer consists of two solutions: Part A (37. 5 g potassium ferricyanid e / 500 mL water) and Part B (240 g/L sodium thiosulfate). Thes e hav e a reasonabl y lon g shelf-life , bu t mixture s o f thes e tw o solutions are effectiv e fo r les s than 3 0 min and, therefore , mus t be prepare d onl y immediately before use . Th e standar d mixtur e is 1 part A with 4 parts B and 30 parts water. Th e slide, negative , or print is agitated i n the solution fo r as long as it takes t o remov e th e unwante d silver . I f 30 mi n elaps e befor e completion , fres h solution mus t b e prepare d an d th e proces s mus t b e repeated . Afte r sufficien t clearing, was h th e fil m i n fiv e volume s o f water , dry , an d mount . Thi s simpl e treatment ca n save you fro m havin g to repea t th e whol e exposure an d processin g routine. It s availability also eliminates rationalizin g the use of a single substandard slide fro m a roll of otherwise goo d frames . There ar e intensifier s tha t migh t be helpfu l fo r correctin g underexposur e an d underdevelopment, but I have not personally tried them. I guess I tend to err on the other sid e i n an attemp t t o hav e very high contrast an d the deepes t possibl e black areas. Th e intensifiers can increase th e contrast o f thin, continuous ton e negatives but ma y be les s usefu l wit h slides .

Reversal Processing for Technical Pan Film

Use the followin g steps i n the dark: 5 minutes 7 0 °C developer (D-1 9 undilute d stock solution) 5 volume water rinse 3 minute bleac h ( 6 g K2Cr2O7 + 7. 5 mL Sulfuric Acid pe r 500 mL water) 5 volume water rins e 2 minutes clearing (5 0 g sodium sulfite per 500 mL water) Use the followin g step s i n the light: 5 volume water rins e 30 seconds per side of reel reexposure with 100 W bulb ca. 30 cm 1 minute Developer (D-19 a s above)

5 volume water rinse

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REFERENCES Frost, T.M. an d PA . Jones . 1982 . Do-it-yoursel f blac k and whit e slides. Bull . Eco . Soc . Amer . 63:16-17. Homer, J. A, and C. Pennington. 1974 . A simple and rapid method o f adding color t o photographi c projection materials . Southeas t Electro n Microscop y Societ y Abstracts . Kodak #1 . 1975 . Koda k Publicatio n S-30, Plannin g and Producing Slide Programs . Kodak #2 . 1986 . Koda k Publicatio n S-24, Legibility : Artwor k t o Screen . Kodak #3 . 1987 . Koda k Publicatio n M3-106, Makin g lecture slides. Kodak #4 . 1982 . Koda k Publicatio n M3-515, Makin g lecture slides: Workshee t #1 . Kodak #5 . 1982 . Koda k Publicatio n M3-516, Making lectur e slides: Worksheet #2 . Kodak #6 . 1985 . Koda k Publication S-26, Reverse-tex t slides . Kodak #7 . 1987 . Koda k Publicatio n P-15, Koda k film s fo r lecture slides. Kodak #8 . 1982 . Koda k Publicatio n P-255, Kodak Technical Pan Film 2415 . Kodak #9 . 1984 . Koda k Publicatio n F-5, Koda k Professiona l Black and White Films. Kodak #10 . 1983 . Koda k Publicatio n G-73, Koda k Precisio n Line Films. Xerox. 1985 . Communicat e effectivel y wit h slides. Reorde r Number 610P153110. Xero x Repro duction Centers , Xero x Square , Rochester , N Y 14644 . (Ver y nic e bookle t put s muc h of thi s appendix down i n an outlin e with color examples. ] CONSULTANT Frank B . Salisbury Utah Stat e University Logan, Uta h

c GUIDELINES FOR MEASURING AND REPORTING ENVIRONMENTAL PARAMETERS FOR PLANT EXPERIMENTS IN GROWTH CHAMBERS Developed b y the American Society of Agricultural Engineers Environment of Plant Structures Committee ; approve d b y th e ASA E Structure s an d Environmen t Standards Committee ; adopte d b y ASAE , Marc h 1982 . Revise d Marc h 1986 ; reconfirmed Decembe r 1989 ; revise d Februar y 1992 3. Submitted by: John C . Sager NASA, Joh n F . Kennedy Space Cente r KSC, FL, 32899-0001 U.S.A. Donald T . Krizek USDA Climat e Stress Laborator y U. S. Department o f Agriculture, ARS , Beltsville, M D 20705-2350 U.S.A . Theodore W . Tibbitts Department o f Horticultur e University of Madiso n Madison, WI 53706-1590 U.S.A . SECTION 1: PURPOSE AND SCOPE 1.1 Th e purpos e o f thi s Engineerin g Practic e i s t o se t fort h guideline s fo r th e measurement of environmental parameters that characterize the aerial and root environment i n a plant growth chamber. 1.2 Thi s Engineering Practice establishes criteria that will promote a common basis for environmenta l measurements for the research community and the commercial plant producer . 1.3 Thi s Engineering Practic e promote s uniformit y an d accuracy in reporting data and result s i n the cours e o f conducting plant experiments.

Submitted Jul y 16 , 1993 ; include s a fe w recen t modifications . Thi s i s ASAE Engineerin g Practice: ASA E EP 411. 2 202

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SECTION 2: INTRODUCTION 2.1 Th e aeria l environmen t i s characterize d b y th e followin g parameters : ai r temperature, atmospheri c compositio n includin g moisture an d carbon dioxid e concentration, ai r velocity, radiation, and the edge effects o f wall/floor on thes e parameters. 2.2 Th e roo t environmen t i s characterized b y the followin g parameters : mediu m composition and quantity, nutrient concentrations, wate r content, temperature , pH, electrica l conductivity, an d oxygen concentration . 2.3 Measurin g an d reportin g thes e variou s parameter s wil l b e covere d i n th e sections that follow . Th e definitions of the parameters indicat e th e symbol and units i n th e forma t (symbol , units) . Measurement s shoul d b e mad e tha t accurately represen t th e mea n an d range o f the environmenta l parameter s t o which th e plant s ar e expose d durin g the experimenta l period , t o indicat e th e temporal variations , both cyclic and transient, and the spatial variations over th e separate plants in th e chamber . 2.4 Th e definitions , measuremen t techniques , an d reportin g procedure s provid e criteria an d promot e uniformit y i n measurin g an d reportin g environmenta l parameters, bu t these guidelines should not be used to select the environmenta l parameters applicabl e t o a particula r experiment . Othe r parameter s ma y be applicable t o a particular experiment or special environments such as elemental concentration i n hydroponi c solutions , pollutan t concentratio n i n ai r qualit y research, and spectra l qualit y ratios i n photobiology . 2.5 Whe n measurement s ar e made , th e chambe r shoul d b e operatin g wit h con tainers an d plant s locate d i n th e chamber . Provisio n shoul d be mad e t o tak e all measurements wit h minimum disturbance t o th e operating environment . SECTION 3: DEFINITIONS 3.1 Radiation: The emission and propagation of electromagnetic waves or particles through spac e o r matter . 3.1.1 Radiant energy (Q e, J): Th e transfe r o f energy of radiation . 3.1.2 Energy flow rate ( e , W) : Th e rat e o f flo w o f energy , a fundamental radiometric unit ; also called radiant power. 3.1.3 Spectral distribution: A functional or graphic expression o f the relatio n between th e spectra l energ y flux, spectra l photo n flux , o r fluence rate pe r uni t wavelength, an d wavelength . 3.1.4 Spectral energy flow rate ( e y , W-nm" 1): Th e radian t energ y flow rate per uni t wavelength interva l a t wavelengt h Y 3.1.5 Energy flux (E e, W.m- 2): Th e radian t energ y flow rate pe r uni t plan e (flat) surfac e area ; als o calle d irradiance . 3.1.6 Spectral energy flux (E e,y , W.m-2.nm- 1): Th e radian t energ y flo w rat e per uni t plane surfac e per uni t wavelength interval a t wavelength Y.

204 Appendices:

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3.1.7 Energy fluence (F e, J.m- 2): Th e radian t energy dose tim e integra l pe r unit spherica l area . 3.1.8 Spectral energy fluence (Fei, J.m-2.nm- 1): Th e energy fluence per uni t wavelength interva l a t wavelength y 3.1.9 Energy fluence rate (F et, W.m- 2): Th e radiant energ y fluence per uni t time. Th e sam e a s radiant energ y flux (irradiance) fo r norma l inciden t (perpendicular) radiatio n o n a plane surface. 3.1.10 Spectral energy fluence rate (F e,t,y, W.m-2.nm- 1): Th e radian t energ y fluence rate per uni t wavelengt h interva l a t wavelength y 3.1.11 Photon (uni t = q ; i.e., one photon): A quantum (the smallest, discret e particle) o f electromagneti c energ y with an energ y of hc/A. ( h = Planck' s constant; c = speed o f light; y = wavelength). It s energy is expressed in joules (J). 3.1.12 Photon flow rate ( p , q.s- 1 or mol-s- 1): Th e rat e o f flow of photons. 3.1.13 Photon flux (E p, q-m-2.s-1 or mol-m-2.s- 1): Th e photo n flo w rat e pe r unit plane surface area; sometimes als o called photon flux density to emphasize the unit area . 3.1.14 Spectral photon flux (Ep,y, q-m-2.s-1.nm- 1 o r mol-m-2.s-1.nm-1) : The photo n flux per uni t wavelength interval at wavelength A. 3.1.15 Photon fluence (F p, q-m"2 or mol-m" 2): Th e photo n flow rate pe r uni t spherical area . 3.1.16 Photon fluence rate (F pt, q.m-2.s- 1 o r mol-m- 2.s-1): Th e photo n fluence per uni t time . Th e same as photon flux for normal inciden t radiation. 3.1.17 Spectral photon fluence rate (F ptli, q-m-2.s-1.nm- 1 o r mol-m- 2-s4 •nm-1): Th e photon fluenc e rat e pe r unit wavelength interval at wavelength y 3.1.18 Light: Visuall y evaluated radiant energy, with wavelengths approximately ranging between 38 0 and 78 0 nm, based on sensitivit y of the huma n eye. 3.1.19 Illuminance (Ev . 1x): The luminous flux (light incident pe r uni t area) . NOTE: (a) Radiation instrument s that measure illuminance are not recommended. The y shoul d onl y b e use d alon g wit h recommende d radiatio n instruments for historical comparison , (b) Conversion factor s from illumi nance t o radiation ar e spectrally sensitiv e an d thus unique for each specified source. 3.1.20 Photosynthetically active radiation (PAR, q.m- 2.s-1, mol-q-m- 2. s 4 , or W-m- 2): Th e radiatio n i n the wavelength rang e of 400-700 nm . Measure d as th e photosyntheti c photo n flu x (PPF), i n quanta.m- 2-s-1, or mol.m- 2-s-1 or photosyntheti c irradianc e (PI) in W-m- 2 for th e specifie d waveband , y1-y2 (400-700 nm). 3.1.21 Photomorphogenic radiation (q.m- 2.s-1, mol.m- 2.s-1, o r W-m- 2): The radiatio n wit h wavelength s approximatel y ranging between 300-80 0 n m contributing t o photomorphogeni c response s (i.e. , phototropism , flowering ,

Guidelines for Reporting Environmental Parameters 20

5

reproduction, elongation , dormancy ) i n relatio n t o th e relativ e quantu m efficiency o f th e spectra l qualit y of th e radiatio n i n severa l discret e spectra l regions. Measure d a s the photo n flux in average quant a .m-2.s-1, or i n energy flux in W-m" 2 for th e specifie d waveband, y1-y2. NOTE: Th e specfi c response s t o photomorphogeni c radiatio n mus t b e biologically quantifie d and carefull y measured fo r eac h response spectrum (action spectrum). 3.2 Temperature: Th e therma l state o f matter wit h referenc e t o it s tendenc y t o transfer heat. A measure o f the mean molelcular kineti c energy of that matter . 3.2.1 Temperature, dry bulb (T, °C) : Th e temperature of a gas or mixtur e of gases indicate d b y a n accurat e thermomete r protecte d fro m o r correcte d fo r radiation effects . 3.2.2 Temperature, wet-bulb (Tw, °C) : Wet-bul b temperature i s the tempera ture indicate d b y a wet-bul b sensor o f a psychromete r constructe d an d use d according t o instructions . 3.2.3 Temperature, dewpoint (Td, °C) : Th e temperatur e o f a n ai r mas s a t which th e condensatio n o f water vapo r begin s a s th e temperatur e o f th e ai r mass i s reduced . Also , th e temperatur e correspondin g t o saturatio n vapo r pressure (10 0 % relative humidity ) for a given air mass at constan t pressure . 3.3 Atmospheric moisture: Th e water vapor component of the mixture of gases of the atmosphere . 3.3.1 Water vapor density (P r, g.m-3 or Pa) : Th e rati o o f th e mas s of water vapor t o a given volume o f air, als o calle d absolut e humidity . I t ma y also b e measured a s partial pressure . (Wate r vapo r pressure). 3.3.2 Relative humidity (Hr, percent): Th e ratio of the mol e fraction o f water vapor present i n the air to the mole fraction of water vapor present in saturated air at the same temperature and barometric pressure. I t approximates the ratio of the partial pressure o r density of the water vapor in the air to the saturation pressure or densit y of water vapor at th e same temperature . 3.3.3. Water vapor deficit (e d, Pa): Th e differenc e betwee n saturatio n wate r vapor pressur e a t ambien t temperatur e an d actual vapor pressur e a t ambien t temperature. 3.4 Air velocity (V, m-s-1): Th e tim e rate of air motion along a directional vector . 3.5 Carbon dioxide concentration ([CO 2], umol-mol-1 or Pa) : Th e carbon dioxid e component o f th e mixtur e of gases o f th e atmosphere . Curren t expressio n o f units of equivalent gas concentration ar e iimol-mol- 1, parts per million (ppm), or u-L-L- 1, bu t the y d o no t expres s standar d temperature an d pressure , STP, correction. Us e o f partia l pressure , Pa , i s preferre d i n nonstandar d atmospheres. 3.6 Watering (volume, L): Th e additio n of water to th e substrat e specified a s t o the source , th e times , the amount , and the distribution method.

206 Appendices:

Presenting Scientific Data

3.7 Substrate: Th e medi a comprisin g th e roo t environmen t specifie d a s t o type , amendments, an d its dimensions (containe r size) . 3.8 Nutrition: Th e organic an d inorganic nutrient salt s necessary fo r plant growt h and development . Formul a and/o r macr o an d micr o nutrient s ar e specifie d within th e substrat e a s mol-m- 3 or within liquid solution a s mol-L-1. 3.9 Hydrogen ion concentration (p H units) : Th e hydroge n io n concentratio n measured i n th e substrat e o r liqui d media over a range of 0 to 1 4 pH units . 3.10 Electrical conductivity (y c, mS.rn- 1): Th e electrica l conductivit y withi n th e solid o r liqui d medium . 3.11 Accuracy : Th e exten t t o whic h the reading s o f a measuremen t approac h th e true values o f a single measure d quantity . 3.12 Precision: Th e abilit y of the instrumen t t o consistently reproduc e a value of a measured quantity . SECTION 4: INSTRUMENTATION 4.1 Radiation. Sensor s shoul d b e cosin e correcte d an d constructed o f material of known stability, known response curve , and lo w temperature sensitivity . Suc h relationships shoul d b e specifie d an d availabl e fo r eac h sensor . B y definition fluence measurement s can only be taken with spherical sensor s an d cannot b e derived fro m measurement s take n wit h any plane-surface sensors. Th e sensi tivity an d linearit y ove r th e spectra l respons e an d irradianc e rang e shoul d b e specified by calibration o r direct transfer from a calibrated instrument . Spectra l measurements shoul d be made with a bandwidth of 20 nm or less in the 300-800 nm waveband. 4.2 Temperature. Sensor s should b e shielded with reflective material and aspirated (> 3 m.s- 1) fo r air measurements . 4.3 Atmospheric moisture. Measuremen t shoul d b e mad e b y infrare d analyzer , dewpoint sensor , or psychromete r (shielde d an d aspirated at > 3 m.s- 1). 4.4 Air velocity. Senso r should hav e a range of 0.1 to 5. 0 m.s- 1. 4.5 Carbon dioxide. Measuremen t shoul d b e made by an infrare d analyze r with a range o f 0 to 100 0 umol-mol- 1 o r greater . 4.6 Hydrogen ion concentration. Senso r shoul d hav e a rang e o f 3. 0 t o 10. 0 p H units. 4.7 Electrical conductivity. Senso r shoul d have a range of 1 to 10- 2 mS.m-1 (1-100 milliohms resistance) . 4.8 Expected instrument precision and measurement accuracy. Tabl e 1 gives these percentages, whic h indicate full scal e precisio n or accuracy . Furthe r definition of thes e requirements ca n be foun d i n reference 27.

Guidelines for Reporting Environmental Parameters 20

7

Table 1. Expected Instrument Precision and Measurement Accuracy Measurement Parameter Instrumen t accurac y of precision readin g Radiation Flux Spectral flux Temperature

±1 % ±1%

±10% ±5%

± 0. 1 °C

± 0. 2 °C ± 0. 2 °C

Relative humidit y Dewpoint temperatur e Water vapo r densit y Air velocity Carbon dioxid e

±2% ± 0. 1 °C

± 0. 1 g.m'3 ±2% ±1 %

±5 % ± 0. 5 °C ± 0. 1 g.m-3 ±5 % ±3 %

H+ concentratio n Electrical conductivit y Salt concentratio n

± 0. 1 pH

± 0. 1 pH

±5%

±5%

Air

Soil or liqui d

Atmospheric moistur e

PH

± 0. 1 °C

SECTION 5s MEASUREMENT TECHNIQUE 5.1 Photon and energy flux. Measurement s shoul d b e take n ove r th e to p o f th e plant canop y t o obtai n th e average , maximum , and minimum readings, an d a t least a t th e star t an d en d o f each stud y and biweekl y if studies exten d beyon d 14 days. 5.2 Spectral photon or energy flux. A measurement should be taken at th e center of the growin g area, at leas t a t th e star t an d end of each study. 5.3 Air temperature. Measurement s shoul d be made at the top of the plant canopy at leas t daily , 1 h o r mor e afte r eac h ligh t an d dark perio d begins , t o obtai n average, maximum , an d minimu m data . Continuou s measurement s ar e recommended. 5.4 Soil and liquid temperatures. Measurement s shoul d be made at th e cente r of the containers in the growing area, obtaining average, maximum, and minimum readings a t th e middl e of the light and dark periods at th e start o f the experi ment. Continuou s measurement s during the entire study are recommended . 5.5 Atmospheric moisture. Measurement s should be made at the top o f the plan t canopy in the center o f the growing area daily, 1 h or more after eac h light and dark period. Continuou s measurement s are recommended . 5.6 Air velocity. Measurement s shoul d be taken at th e to p of the plan t canopy, at the star t an d en d o f th e studies . Obtai n average , maximum , an d minimu m readings over th e plants . I f instantaneous devices are utilized , 10 consecutive readings should be take n a t eac h locatio n an d averaged.

208 Appendices:

Presenting Scientific Data

5.7 Carbon dioxide. Measurement s shoul d be taken at the top of the plant canopy continuously durin g th e perio d o f th e study . A time-sharin g techniqu e tha t provides a periodi c measuremen t (a t leas t hourly ) i n eac h chambe r ca n b e utilized. 5.8 Watering. Th e quantity of water added t o each container o r average per plan t at eac h waterin g shoul d b e measured . Soi l moistur e shoul d b e measure d t o provide th e rang e betwee n waterings . 5.9 Nutrition. Measuremen t o f nutrients added to a volume of medium or concen tration o f nutrients added in liquid culture should be obtained at each addition . 5.10 Hydrogen ion concentration. Th e pH o f th e liqui d solution s i n a nutrien t culture system should be monitored dail y and before each pH adjustment. Th e pH o f the solutio n extracte d fro m soli d medi a should be measured at th e star t and en d o f studies an d befor e and afte r eac h pH adjustment . 5.11 Electrical conductivity. Conductivit y o f th e liqui d solution s i n a nutrien t culture syste m shoul d b e monitore d dail y durin g th e cours e o f eac h study . Conductivity of the solution extracted fro m soli d media should be measured a t the star t an d en d o f each study. SECTION 6: REPORTING 6.1 Photon or energy flux. Report th e average and range over the containers a t the start o f th e study , and th e decreas e o r fluctuation s fro m th e averag e ove r th e course of the study. Th e source of radiation and the measuring instrument/sensor should be reported. Illuminanc e should not be reported excep t fo r historical compariso n i n conjunction with other radiatio n measurements . 6.2 Spectral photon or energy flux. Report the spectral distribution (graphical) and the integra l (photo n o r energ y flux ) a t th e star t o f the study . Th e sourc e o f radiation an d th e measurin g instruments should be reported. 6.3 Air temperature. Repor t th e averag e dail y readings with extreme s ove r th e growing area for the light and dark periods with the range of variations over th e course of the study. 6.4 Soil and liquid temperatures. Repor t th e averag e readings a t th e star t o f th e study fo r th e ligh t and dar k periods . 6.5 Atmospheric moisture. Repor t the dail y average moisture level fo r both light and dark periods with the rang e over th e cours e o f the study. 6.6 Air velocity. Repor t the average and range over containers at the start and end of th e study . 6.7

Carbon dioxide. Repor t th e mea n of hourly average concentrations an d range of averag e readings over the perio d of the study .

6.8 Watering. Repor t th e frequenc y o f watering , source , an d amoun t o f water added dail y t o eac h container , and/o r th e rang e i n soi l moistur e conten t between waterings.

Guidelines for Reporting Environmental Parameters 20

9

6.9 Substrate. Repor t th e type of soil and amendments, or components of soilless substrate, and container dimensions. 6.10 Nutrition. Repor t the nutrient s added t o solid media . Repor t th e concentra tion of nutrients in liquid additions and in liquid culture solution along with the amount and frequenc y of all additions. 6.11 Hydrogen ion concentration. Repor t th e mode and range in p H over the perio d of th e study. 6.12 Electrical conductivity. Report th e average and range in conductivity over th e period o f the study.

SECTION 7: SYNOPTIC TABLE 7.1 Tabl e 2 is a synoptic table o f the materia l presente d i n th e previou s section . Table 2. Guidelines for Measuring and Reporting Environmental Parameters for Plant Experiments in Growth Chambers* Measurements Parameter Units

a

Radiation Photon flux y1 - y 2 nm , with cosin e correction o r

umol.m-2.s-1 (y1 -y2 nm) or

Energy flux (Irradiance) , y1 - y 2 n m with cosine correction

W.m-2 (y1 -y2 nm )

Where to take Whe At to p o f plant canopy. Obtain maximu m and minimum over plan t growing area.

n to take Wha Minimum measurements : at star t and finis h o f each study and biweekl y if studies extend beyond 1 4 d.

t t o report Average ( ± extremes ) ove r containers a t start o f study. Percent decreas e o r fluctu ation fro m averag e ove r the cours e of the study. Source o f radiation and instrument/sensor.

Continued

Spectral photon flux y1 - y2 nm, i n < 20 n m bandwidths with cosin e correction o r

umol.m-2.s-1.nm-1 (y1 - y 2 nm) or

Spectral energy flux (Spectral irradiance) y1 - y 2 nm , in <10 nm bandwidths with cosin e correction

W.m-2.nm-1 (y1 - y2 nm)

Photosynthetic photon flux, PPF,C y400 - y700 nm with cosine correction o r

umol.m-2.s-1 (y400- y70 0 nm ) or

Photosynthetic irradiance, PI,C y400 - y700 nm with cosine correctio n

W.m-2

At to p o f plant in center of growing area.

Minimum measurement : at star t an d end o f each study.

Spectral distributio n of radiation with integral (y 1 - y 2) a t star t o f study. Source of radiation an d instrument/sensor.

At to p of plant canopy. Obtain maximu m and minimum over plan t growing area.

Minimum measurement: at star t an d finis h o f each study and biweekl y if studies extend beyond 1 4 d.

Average ( ± extremes ) ove r containers a t star t o f study. Percent decreas e or fluctu ation fro m averag e ove r the cours e of the study . Source of radiation an d instrument/sensor.

(y400- y70 0 nm )

Temperature Air Shielded an d aspirate d (> 3 m.s-1) device

°C

At to p of plant canopy. Obtain maximu m and minimum over plan t growing area.

Minimum measurement : measure once daily during each ligh t an d dark perio d at leas t 1 h after ligh t change. Desirable : contin uous measurement .

Average o f once daily readings (o r hourl y average values) fo r th e ligh t an d dar k periods o f the stud y with ± extremes for th e variation over th e growin g area.

Temperature Soil and liqui d

°C

In cente r o f container . Obtain maximum and minimum ove r plan t growing area.

Minimum: measur e a t th e middle o f the ligh t and dark periods a t the star t of the study . Desirable : con tinuous measurement .

Light an d dark perio d readings at th e star t o f th e study (o r hourl y average values of 2 4 h i f taken).

Continued

Table 2. Guidelines for Measuring and Reporting Environmental Parameters (continued) Measurements Parameter Units Atmospheric Moistur e Relative humidit y (RH ) with aspirated psychrometer, dewpoint hygrometer , or IRG A or

a % RH , dewpoin t temperature, or g-m"3 or

Where to take Whe

n to take Wha

t to report

At to p o f plant canopy in center o f plant growin g area.

Minimum: onc e during each ligh t an d dark perio d at least 1 h after light changes. Desirable : continuous measurement.

Average o f daily readings for bot h ligh t and dark periods, with range of daily variation during studies.

Vapor deficit , VP D or vapo r difference

kPa o r g-m- 3

Air Velocity

m.s-1

At to p o f plant canopy. Obtain maximu m an d minimum reading s over growing area .

At star t an d end o f studies . Take 1 0 successive readings at each locatio n and age .

Average readin g and range over containers a t start and end o f th e study .

Carbon Dioxide Mole fractio n

nmol-mol

At to p o f plan t canopy

Partial pressure Concentration

Pa raol-m

Minimum: hourl y measurements. Desirable : continuous measurements.

Mean o f hourly average concentrations an d range of average concentration s over th e perio d o f the study.

Watering

liter (L )

Substrate

At time s of water addi tions.

Frequency o f watering. Amount of water adde d and/or rang e i n soil moisture content betwee n waterings.

At beginnin g of studies.

Type of soil and amendments. Component s o f soilless substrate. Wate r retention capacity . Con tainer dimensions . Continued

Nutrition

Soil media mol-m-3 o r mol-kg-

1

At time s of nutrient additions.

Nutrients added t o solid media. Concentratio n o f nutrients in liquid additions and solution culture . Amount an d frequenc y o f solution additio n and re newal.

Liquid cultur e mol-L-1

pH

pH unit s

In saturate d media, extract from media o r in solution of liquid culture.

Start an d end of studies in solid media. Dail y in liquid culture. Befor e each pH adjustment.

Mode an d range durin g studies.

Electrical conductivit y

mS-m-ld (millisie mens per meter )

In saturated media, extrac t from medi a or i n solution of liquid .

Start and end of studies in solid media . Dail y in liquid culture.

Average an d range durin g studies.

"USDA Nort h Central Regiona l (NCR 101) Committee on Controlled Environment Technology and Use , June 1978; Revise d b y ASAE Environment of Plant Structure s Committee , Oc t 1978; Revise d by NCR 10 1 Committee, March 1993. Publishe d in par t in th e following references: 1 , 17, 18, 22, 27, 28, 34, and 37 . a r

Repor t in other subdivisions of indicated unit s if mor e convenient The energ y flu x (irradiance ) is also commonly reported i n J.m-2.s-1 (equals W.m-2) .

c

Referre d t o as photosynthetically active radiation (PAR) fo r general usage .

d

mS.m- 1 = 1 0 umho-cm- 1.

214 Presenting

Scientific Data BIBLIOGRAPHY

American Societ y fo r Horticultura l Scienc e Working Group o n Growt h Chamber s an d Controlle d Environments. 1980 . Guideline s fo r measurin g and reportin g th e environmen t fo r plant studies. HortScienc e 15(6):719-720. ASAE. 1988 . ASA E Engineering Practice: ASA E EP285.7, Use of SI (Metric) Units. Ameri can Societ y o f Agricultural Engineers , St. Joseph, M I 49085. ASAE. 1985 . ASA E Engineering Practice : ASA E EP402, Radiation Quantitie s an d Units . American Societ y o f Agricultural Engineers , St . Joseph, MI 49085. Bell, C.J . an d D.A . Rose . 1981 . Ligh t measurement an d th e terminolog y of flow. Plant , Cell an d Environment 4:89-96 . Bickford, E.D . an d S . Dunn. 1972 . Lightin g for Plan t Growth. Th e Ken t Stat e University Press, Kent, Ohio . Biggs, W.W. an d M.C . Hansen . 1979 . Instrumentatio n for biologica l an d environmenta l sciences . LI-COR Inc . Lincoln , Nebraska . C.I.E. 1970 . Internationa l Lightin g Vocabulary. Publ . No. 17 . Commission Internationale de I'Eclairage, Paris , France. Downs, RJ . 1975 . Controlle d Environment s fo r Plant Research. Columbi a Universit y Press, New York, NY . Downs, R.J . 1988 . Rule s fo r usin g the internationa l systems o f units. HortScienc e 12(5):811-812 . Geist, J . an d E . Zalewski . 1973 . Chines e nomenclatur e fo r radiometry. Applie d Optic s 12:435 436. Holmes, M.G. an d L . Fukshansky . 1979 . Phytochrom e photoequilibriu m in green leave s unde r polychromatic radiation : a theoretica l approach . Plant , Cel l and Environmen t 2:59-65. Holmes, M.G. , W.H . Klei n and J.C . Sager . 1985 . Photons , flux , an d som e ligh t o n philology. HortScience 20(1):29-31 . IES Lightin g Handbook. 1981 . Fift h edition . Illuminatin g Engineering Societ y o f North Ameri ca, New York, NY . Incoll, L.D., S.P . Lon g and M.R . Ashmore . 1977 . S I units in publications in plant science. Current Advance s i n Plant Scienc e 9(4):331-343. Kerr, J.P. , G.W . Thurtel l an d C.B . Tanner . 1967 . A n integrating pyranometer fo r climatological observer station s an d mesoscal e networks . Journa l of Applied Meterolog y 6:688-694 . Kozlowski, T.T. , editor . 196 8 an d 1976 . Wate r Deficit s an d Plan t Growth . Vol . 1 , Development , Control an d Measurements . Vol . 4 , Soil Wate r Measurement , Plan t Responses and Breeding for Drough t Resistance . Academi c Press , Ne w York, NY . Krizek, D.T . 1982 . Guideline s fo r measurin g and reportin g environmenta l conditions i n controlled-environment studies . Physiol . Plant. 56:231-235. Krizek, D.T . an d J.C . McFarlane . 1983 . Controlled-environmen t guidelines . HortScienc e 18(5):662-664 and Erratu m 19(1):17 . Langhans, R.W. , editor . 1978 . A Growt h Chambe r Manual . Cornel l University Press, Ithaca , New York. LI-COR. 1982 . Radiatio n measurement s an d instrumentation . Publ . No. 8208-LM. LI-COR , Lincoln, Nebraska . McCree, KJ . 1972 . Tes t o f current definition s o f photosynthetically active radiatio n agains t leaf photosynthesis data . Agricultura l Meteorology 10:443-453 . McFarlane, J.C . 1981 . Measuremen t an d reportin g guidelines for plan t growt h chamber environ ments. Plan t Science Bulleti n 27(2):9-ll. Mohr, H . an d E . Schafer . 1979 . Gues t Editorial—Unifor m terminolog y for radiation : A critical comment. Photochemistr y and Photobiolog y 29:1061-1062. Monteith, J.L. 1984 . Consistenc y and convenienc e in the choic e of unit s fo r agricultura l science . Experimental Agriculture 20(2):105-117.

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NBS Technical Note 910-2. 1978 . Self-Stud y Manual on Optica l Radiation Measurements , Par t 1—Concepts. Unite d State s Government Printin g Office, Washington , DC. Norris, K.H . 1968 . Evaluatio n of visible radiation for plant growth. Annua l Review of Plant Physiology 19:490-499 . North Centra l Regiona l 10 1 Committee o n Growth Chambe r Use . 1986 . Qualit y assuranc e procedures for environmenta l contro l an d monitorin g in plant growth facilities. Biotronic s 15:81-84. Percival Manufacturin g Co. 1981 . Guidelines : Measuring and Reportin g Environmen t fo r Plant Studies. Availabl e as a plastic card. Rosenberg, N.J . 1974 . Microclimate : Th e Biologica l Environment. Joh n Wile y & Sons, New York, NY. Rupert, C.S . an d R . Latarjet . 1978 . Towar d a nomenclature and dosimetric scheme applicable to all radiations . Photochemistr y an d Photobiology 28:3-5 . Salisbury, F.B. an d C.W . Ross. 1991 . Plan t Physiology. Fourt h edition . Wadswort h Publishin g Co., Belmont , California. Sestak, Z., J. Catsk y and P.G . Jarvis , editors. 1971 . Plan t Photosynthetic Production, Manual of Methods. Junk , The Hague, Netherlands . Slatyer, R.O. 1967 . Plant-Wate r Relationships. Academi c Press, New York, NY. Spomer, L.A 1980 . Guideline s for measurin g and reporting environmenta l factors in controlle d environment facilities . Commun . Soil Science an d Plan t Analysis 11(12):1203-1208. Spomer, L.A . 1981 . Guideline s for measuring and reportin g environmenta l factors in growth chambers. Agronom y Journal 73(2):376-378 . Thimijan, R.W . an d R.D . Heins . 1983 . Photometric , radiometric, and quantu m light unit s of measure: A review of procedures fo r interconversion . HortScienc e 18(6):818-821 . Tibbitts, T.W . an d T.T . Kozlowski , editors. 1979 . Controlle d Environmen t Guidelines for Plant Research. Academi c Press , Ne w York, NY. Tooming, K.G. 1977 . Sola r Radiatio n an d Yiel d Formation (Solnechnay a radiatsiya i formirovanio urozhaya) Gidrometeoizdat , Leningrad . Zelitch, I . 1971 . Photosynthesis , Photorespiratio n an d Plan t Productivity. Academi c Press , Ne w York, NY .

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INDEX Air, 7 temperature, 207-208 velocity, 205-208 , 21 2 Alanine, 89 Algebraic valency, 57 Aliasing, 12 9 Allele, 97 Allelopathic substances, 13 4 Allocation, 72 Allohydroxylysine, 89 Allometry, 11 1 Ambiphotoperiodic plants, 13 4 Ameliorate, 144 Amino acid residues, 85 Amino acids, 93 Amount of pure substance (mol), 5-6, 57 AMP, 87 Ampere (A), 5-7 Ampersand, 23 Amplified-fragment-length polymorphism , 97 Amplitude, 129 Anaerobic stress, 14 6 Analysis of variance, 32 Anamorphs, 25 And, 164, 168 Angstrom (obsolete), 14 , 18 Anisotropic growth, 11 1 Annual, 129, 134 Antecedent, 17 5 Anthesin, 13 4 Anthesis, 13 5 Antiauxin, 126 Anticodon, 97 Antiflorigen, 13 5 Antitranspirant, 151 Apex, 13 5 Apiaceae, 22 Apical: cell, 113 meristem, 13 5 Apostrophe, 177 , 180 Arabic numerals, 5 Arabinose, 90 Arbitrary rules, 16 3 Area, 5, 9 Arecaceae, 22 Arginine, 89 As, 179, 18 1

A (symbol for amp), 6 Abbreviations, 178 , 186 Abortion, 13 4 Abscissa, 18 9 Abscission, 13 4 Absolute, 18 3 growth rate, 111, 118 response, 134, 139 Absorbance, 76-77 , 83, 87 Absorptance, 6 5 Absorption: coefficient, 6 5 factor, 76 Absorptivity, 6 5 Abstract, 18 3 Acceleration: caused by gravity, 1 7 of free fall, 1 8 Accelerational force , 6 Accept, 17 9 Acclimation, 143 , 154 Accuracy, 206 ACES, 92 Acronyms, 17 8 Acrophase, 12 9 Active, 18 6 voice, 17 6 Activity, 56 coefficient, 5 6 of radioactive source , 9 ADA, 92 Adaptation, 122 , 143 Addition (plus) sign, 25 Adenine, 91 Adenosine, 91 Adjectival sense , 11 , 14 Adjective(s), 23 , 164-165, 169-170, 181 , 185 ADP, 87 ADPglucose synthase , 10 6 Advection frost , 14 8 Adverb(s), 164-165 , 169, 171-170, 177 , 185 Adverbial forms, 18 5 Aero-, 12 4 Affect, 17 9 AFLP, 97 After-ripening, 13 4 Ageo-, 12 3 Agravi-, 12 3

217

218 Index Asparagine, 8 9 Aspartic acid, 89 Asteraceae, 22 Articles, 16 9 Artwork, 188, 190, 192-193 Atmospheric moisture, 205-208, 21 2 Atomic mass unit (u), 83 Atoms, 7 ATP, 8 7 Atto (prefix = a), 8 Attributive adjective, 18 2 Auditorium, 19 9 Author(s), 23-24 Authorities, 2 3 Autocatalytic growt h function, 111 Autonomous, 121 , 124 Autonomously-inductive plant, 135 Autonyms, 23 Autotropism, 12 5 Auxin, 126 antagonist, 126 Average, 55 Avoidance, 14 3 response, 12 4 Avogadro's number, 7 (mole) of photons, 7 5 Axillary meristem, 13 5

Black-and-white artwork, 192 Blackfrost, 14 8 Blasting, 134 Blindness, 134 Blocking, 27 Blocks (statistics), 3 9 Blue background slides, 199 BlOhreife, 13 9 Boldface, 17 , 164 Bolting, 135 Botanical congresses, 21 Bound: auxin, 126 water, 15 2 Boundary layer, 65 resistance, 6 7 Bowing, 12 1 Brackets, 173 , 174, 177, 186 Branch point, 97 Brassicaceae, 2 2 Bromouridine, 91 Build-up routine, 189 Bulging, 121 Bunsen-Roscoe law, 12 2 Bureau International des Poids et Mesures, 3 Business card, 196 But, 164-165, 167-168

Bacteria nucleation inhibitors, 14 6 Balance (to determine mass), 6 Ballistic transformation, 97 Bar (bar, obsolete), 14 , 18 Bar: charts, 19 6 graphs, 19 1 'Base, a,'91 Base, kilobase (b, kb), 97 Base unit(s) (of the SI), 4-6, 12 , 15 in denominators, 15-1 6 Basic: patterns, 16 5 sentence structures, 16 4 Basis of sequence, 10 6 Because, 180 Becquerel (Bq), 9, 12, 86 Bending, 121 and bulging, 12 1 BES, 92 Bibliographies, 18 0 Bicine, 92 Bidirectional transport , 7 3 Biennial, 13 5 Binomial, 23 Biological: clock, 12 9 cycle, 12 9 rhythm, 130 Biosalinity, 15 4 Biothermodynamics, 93 BIPM, 3-6 BisTris, 92

C (symbol for coulomb), 9 Caesalpiniaceae, 22 Calorie (obsolete), 14 , 18, 86, 143, 146 cAMP, cGMP etc., 87 CaMV, 97 Can, 180 Candela (cd), 5-8

Capitalized, 10, 22-23

CAPS, 92 Caption, 184 Carbohydrates, 94 Carbon dioxide, 206, 208, 212 concentration, 205 4-Carboxyglutamic acid, 89 Carotenoids, 9 5 Case, 171 CAT, 98 Catalytic activity, 93 Cation exchange capacity (CEC), 15 4 Caulescent plant, 135 Cauliflower mosaic virus, 97 Cause, 179 Cavitation, 152 cDNA, 98 CDP, 88 CDTA, 92 Cell: freezing, 14 7 production rate, 111 Celsius (°C), 7, 10 , 12, 14 Centi (prefix = c; nonpreferred), 8 Centimeter, 17 centimetergranvsecond (cgs), 3

Index 21 Central Limi t Theorem, 41 Centrifugation, 1 8 Centromere, 9 7 Cesium-133 atom, 7 CGPM, 3-6, 13, 17 COS, 3, 11 CHAPS, 92 CHAPSO, 9 2 Charge, 5 8 Chemical potential, 5 7 of water, 6 1 Chemical terms, 170 Chemo-, 12 4 CHES, 92 Chilling, 14 4 injury, 144 , 149 -insensitive, 144 repair, 145 requirement, 146 , 151 reversal, 145 -sensitive, 14 5 temperature, 14 5 tolerance, 14 5 treatment, 14 5 Chloride salinity, 15 4 Chloroamphenicol transacetylase, 98 Chloroplasts (plastid) DNA, RNA, 92, 106 Chromatin, 98 Chromatography, 17 7 Chromosome, 9 8 Chronogram, 13 0 Chronology o f isolation, 10 6 Ciliary movements, 12 0 CIPM, 3, 4, 12-1 3 Circadian: pacemaker, 13 0 rhythm, 130 time, 130 Circalunar rhythm, 130 Circannual rhythm, 130 Circasemidian, 13 2 Circaseptan rhythm , 130 Circatrigintan rhythm , 130 Circular, 98 dichroism, 8 9 Circumnutation, 12 5 Cis, 98 Cis-Aconitate, 9 0 Citric Acid, 90 Class (classis), 22 Clause(s), 164 , 168, 172-173, 18 5 Clay dispersion, 15 4 Clock time, 13 0 Closed circular, 98 Clusiaceae, 22 Cm-cellulose, 88 CMP-NeuAc, 87 CMP, 88 CO2 exchange, 117 CoA(orCoASH), 87 CoASAc, 88

Codon, 98 Coding sequence(s), 98, 106 Coefficient, 6 6 convective transfer, 66 heat energy transfer, 66 of determination, 32 of variation, 28 Coherent unit system, 5, 12-13, 16 Cohesion movement, 121 Cold: hardiness, 14 6 injury, 14 6 protection, 14 6 shock, 14 6 Collective, 180 Colon(s), 17 7 Colony, 98 hybridization, 98 Color slide film, 192 , 197 Colors, 192 Comite International des Poids et Mesures, 3 Comma(s), 11, 164-169, 172-174, 176-177 , 185 186 to group numerals, 12 Comma fault (or splice), 167, 176, 185 Commission on Plant Gene Nomenclature, 105 Common Names, 25 Communicate, 164 Communication, 161-162, 188 Compatible solute, 15 4 Compatibility, 98 Complementary: RNA, 92 DNA, 92, 98 Complementation, 98 Completely randomized design, 33 Components of water potential, 51 Composition of solutions and buffers, 8 4 Compound: adjective(s), 169-170 , 177 , 185 nouns, 178 numbers, 170 symbols, 11 units, 12 , 15 Computer graphics, 19 2 Concentration(s), 9, 56, 212 of metabolites, 15 Conclusion, 189 Conditioning, 143, 145 Conduction, 65 Conference Generate des Poids et Mesures, 3 Confidence interval, 29 for a mean, 29 for a proportion, 30 for a variance, 29 Conjugated auxin , 12 6 Conjunction, 164-168 , 179, 181, 185 Conjunctions of time, 167 Conjunctive adverb(s), 167-168, 185 Connectives, 16 7 Constitutive, 98

9

220 Index Construct, 98 Contingency tables , 40 Continuous tone : artwork, 197 slides, 198 Contractions), 177, 18 0 Contrary to fact, 18 3 Control, 12 1 Controlling elements, 9 8 Controversial o r unfamiliar names, 24 Convection, 14 6 Convective: rate of change, 111 transfer coefficient, 70 Convention d u Metre, 3 Coordinate, 16 4 adjectives, 169 , 17 3 clauses, 16 8 Coordinated, 166-16 7 Coordinating conjunction , 164 , 166 , 168 , 176 , 18 5 Copy: editors, 161, 16 3 stand, 192 Correlation coefficient, 32 Corrinoids, 9 5 Cosinor (polar) display, 130 analysis, 130 Cosmid, 98 Coulomb (C), 9 , 12 Counts per minute, 86 Covariance analysis , 3 8 CPGN, 106-10 7 Critical: daylength, 15 2 nightlength l5 2 period 15 2 photoperiod, 135 temperature, 143 , 145-14 6 Crop growth rate, 116-11 8 Cruciferae, 2 2 Cryo-, 98 CT, 13 0 CTP, 8 8 Cubed, 1 1 Cubic: decimeter, 1 7 meter, 12 , 16 Cultivar(s), 21, 25 Cultivated Plants , 2 5 Culture collection, 21 Curie, 8 6 Current, 7 cv (ab. for cultivar), 2 5 Cycles per second (hertz), 86 Cyclic salt, 154 Cyclitols, 95 Cyclonasty, 12 5 Cysteine, 89 Cytidine, 91 Cytokinin, 12 7 -like, 127

Cytoplasmic streaming , 12 0 Cytosine, 9 1 d (symbol fo r day), 1 3 DD (continuous darkness), 13 1 Dalton (Da or D, obsolete), 14 , 17, 83, 86, 98 Damping, 13 0 Dangling participle, 175 Dark break, 131 Dash(es), 166 , 173-174, 177 , 186 Data, 180 , 19 1 Dawn, 130 Day (d), 7, 12-1 3 -neutral plants, 135 Daylength or day length, 135 Deacclimation, 14 3 Dead, 183 DEAE-cellulose, 88 Deci (prefix - d; nonpreferred), 8 Decimal: fractions, 1 2 marker, 4, 11 system, 3 values less than one, 12 Decimeter, 16-1 7 Decussate, 11 3 Definite article, 16 9 Degree(s): angles or latitudes, 11 , 13 centigrade (obsolete), 10, 14 Celsius (°C), 10 , 18 , 11 , 14 kelvin (obsolete; use kelvin without degree), 7 Degree growth stage model (°GS Model), 14 6 Deep supercooling, 146 Dehardening, 143 , 14 7 Dehydration (desiccation), 15 5 avoidance, 15 2 tolerance, 15 2 Deka (prefix = da; nonpreferred), 8 Demonstrative pronoun, 183 Denominator (in SI units), 12 , 15 Density, 7 of dry (unsaturated) air, 68 2-Deoxyglucose, 90 Deoxyribonucleic acid, 98 2'-Deoxyribosylthymine, 92 Dependent, 16 4 clause, 16 6 Deposition rate, 11 1 Derived units 4, 5, 8, 12 Desalination, 155 Desynchronization, 13 1 Determinate, 13 6 growth, 112 Development, 113 Developmental arrest, 136 Devernalization, 13 6 Dia-(not transversal), 124 2,4-Diaminobutyric acid, 89 Diel, 13 1 Difference:

Index 22 between two population means, 30 between two proportions, 3 1 or change in the quantity that follows, 68 Differential thermal analysis, 14 7 Differentiation, 11 3 Diffusion coefficient : 58 , 87 of species/, 66 Diffusive resistanc e within a leaf, 67 Diflusivity, 63 Dihydrouridine, 91 Dihydroxyacetone phosphate, 9 0 Dinesis, 123 Diploid, 10 1 Direct: address, 177 quotations, 17 7 Direction, 122-12 4 Diurnal, 131 Discarded metric units, 14 Discussion section on a poster, 196 Distance, 67 Divergence angle, 113 Divisio, 22 Division, 10-11, 22 DNA, 88, 98 DNPorDnp, 88 , 135 Documentation, 21 Donor, 13 6 Domain, 98 Dormancy, 13 6 Dose, 12 2 Double: commas, 17 4 spaced, 18 3 Downstream, 99 Drought (including: avoidance , escape, resistance, stress, and tolerance), 15 2 DTA, 147 dTDP, dTMP, dTTP, 88 Due to, 180 Dyed, 192 , 198 Dyes, 19 9 Dyne, 3 Dysfunction, 14 5 EC (symbol for electrical conductivity), 155 Ectopic gene, 99 Eddy diflusion coefficient o f gaseous species, 66 Editing, 99 EDTA, 88, 92 Effect, 17 9 EGTA, 88, 93 Einstein (obsolete), 7, 14 , 17 Electrical: capacitance, 9, 58 charge 9 conductance, 9, 58 conductivity (EC), 147 , 155, 206, 208-209, 213 current 5-6, 5 8 impedance, 14 7 potential (difference), 9 , 57

resistance, 58 Electro-, 124 Electrochemical potential, 57 Electrolyte leakage, 147 Electrometric method, 147 Electron: paramagnetic resonance, 89 spin resonance, 89 Electronic "balances", 6 Electrons, 7 Electrophoresis, 99 Electroporation, 99 Ellipses, 17 7 Embryo dormancy, 136 Emissivity in infrared region, 6 8 Emphasis, 176-178 Encoding, 106 Endodormancy, 136 Endogenous, 121 , 136 rhythm, 130-131 Endotherms, 147 Energy, 9 balance equation, 68 flow rate, 203 fluence, 204 fluence rate, 204 flux, 75, 203, 210 English, 194 , 195 classes, 16 3 system, 11 English-speaking: editor, 194 fellow scientist, 195 Enhancer, 99 Enthalpy, 50 change, 87 Entrain, 133 Entrainment, 131 Entropy change, 87 Enzyme commission numbers, 107 Enzymes, 93 Epinasty, 125 Epithet, 23-24 EPPS, 93 Equilibrium: constant, 87 velocity constants, 83 Equivalent (obsolete), 86 Erg (obsolete), 3 Erythrose-4-phosphate, 90 ESP, 155 EST, 99 et, 23 etal., 180 Euhalophyte, 155 Evaporative: cooling, 14 7 demand, 15 2 Evocation, 13 6 ex, 24 exa, 8

1

222

Index

Except, 17 9 Exchangeable sodium percentage, 155 Exclamation: point(s), 174, 176-177 Exclamatory writing, 176 Exogenous, 12 1 Exon, 99 Exotherm, 14 7 Expected instrument precision and measurement accuracy, 206 Experimental: designs, 32 error, 27, 39 unit, 27 Exponential growth function, 112 Exponents, 11 Expressed sequence tag, 99 Expression, 9 9 Extensibility, 63 Extracellular, extraorgan, and extratissue freezing, 147 F (symbol for farad), 9 Fabaceae, 2 2 Factorial experiments, 35 Facultative response, 136 , 139 FAD and FADH2, 88 Fahrenheit temperature scale, 18 Family (familia), 2 2 names, 22 Family, gene, 106 Farad (F), 9 Faraday, 12 Farmers reducer, 19 9 Felt markers, 19 9 Femto (prefix = f), 8 Ferredoxin, 89 Fibonacci sequence, 11 3 Figures, 18 3 Film(s), 198-19 9 recorder, 192 First harmonic; second, third, etc. harmonics, 131 First law of thermodynamics, 4 5 First person, 17 1 personal pronouns, 17 6 Flagellar movements, 120 Flocculation, 15 5 Flooding, 147, 152 Flora, 23 Floral stimulus, 136 Florigen, 127, 136 Flower initiation, 13 6 Fluorescence (including: initial , maximum, variable, terminal), 76 Flux, 58 FMN, 88 Folding effect, 12 9 Foliar absorption coefficient, 6 6 Folic acid, 95 Fonts, 191, 195 For, 16 4 Force, 6-7, 9, 46

Foreign words, 178 Formality, 172 Format, 183, 187 Fractional induction, 136 Free-running rhythm, 131 Free energy, 47 Freeze (including: avoidance, dehydration, desiccation, tolerance), 147 Freezing: extracellular, extraorgan, and extratissue, 147 injury, 14 8 point, 148 point depression, 148 French Revolution, 3 Frequency, 8-9, 76, 131 multiplication and demultiplication, 131 of electromagnetic radiation, 68 Fries, 24 Frost, 148 hardening, stages of, 148 heaving, 148 injury, 14 6 plasmolysis, 148 protection, 148 Fructose, 90 Fructose-6-phosphate, 90 Fructose-2, 6-bisphosphate, 90 Fructose 1 , 6-bisphosphate, 90 Fucose, 90 Fumeric Acid, 90 Fundamental: period, 131 term, 131 Fungi, 22, 24-25 Future tense, 182 Futurity, 182 gn (symbol for standard acceleration due to gravity), 9, 13-14, 18 Galactose, 90 Galvano-, 124 Gases in gases, liquids, and solids, 56 Gauss, 3 GDP, GDP-Man, GDP-Fuc, 88 Gel, 99 2-dimensional, 97 Gene, 99 designations, 105-106 encoding, 107 expression, 99 family(ies), 99, 106 product numbers, 107 symbol, 106 tagging, 99 transfer, 99 Generalized: conductance coefficient, 5 9 force, 5 9 Generative helix or spiral, 113 Generic name, 23 Genitive, 23

Index 22 Genome, 99, 106 Genus, 22-23 Geo-, 12 3 Geographical location, 21 German, 16 3 Germination, 13 7 Gibberellin, 12 7 -like, 12 7 Gibbs energy change (formerly F) , 8 7 Gibbs free energy (G), 47 Giga (prefix = G), 8, 10, 17 Global irradiance , 67 Glucosamine, 90 Glucose-1, 6-bisphosphate , 9 0 Glucose, 90 Glucuronic acid, 90 p-Glucuronidase, 9 9 Glutamic acid, 89 Glutamine, 89 Glyceraldehyde-3-phosphate, 9 0 Glycine, 8 9 Glycophyte, 15 5 GMP, 8 8 Graft-chimeras, 2 5 Grafting, 13 7 Gram, 6, 10 , 17 Gramineae, 2 2 Grammar: English, 164-18 7 as applied to SI units, 13—14 ; checkers, 18 4 Graphic(s), 188-190 elements (e.g., on poster), 196-197 Graphs, 191 Gravi-, 12 3 Gravity, 6-7, 17 Greek mu, 11 , 15 Greek symbols, 5 Growth, 11 2 analysis quantities, 118 field, 11 2 movement, 120 response, 12 3 velocity, 11 2 zone, 113 GSH and GSSG, 8 8 GTP, 88 Guanine, 91 Guanosine, 91 GUS, 99 Guttiferae, 22 h (symbol for hour), 13, 131 Half-cystine, 89 Half-peak band-width, 77 Halomorphic soil, 155 Halophyte, 15 5 Handout(s), 191 , 197 Haploid, 10 1 Hapto-, 123 Hard seed, 13 7

Hardening, 143, 145, 153, 155 Hardiness promoter, 148 Harmonic, 131 Harvest index, 116 Hb, HbCO, HbO2, metHb, 88 Heat, 9 shock, 99 Heat energy: convection, 66 storage, 65 subscript, 66 Heat transfer: coefficient, 7 0 studies, 68 Hectare, 10 , 14, 18 Hecto (prefix = h; nonpreferred), 8 Helio-, 123 Helium balloon, 7 Henry, 10 Hepes or HEPES, 88, 93 HEPPS, 93 Herbarium: 21-2 2 specimens, 21 Hertz, 9-10, 12 Heterogenous: ice nucleation, 148 nuclear RNA, 92 Heterologous, 100 Heteropolymeric proteins, 10 2 Hexagonal (H,l) phase, 149 High contrast artwork, 198 High frequency oscillations, 131 Histidine, 89 Histone, 100 Hoarfrost, 14 8 Homeohydric plant, 149 Homocysteine, 89 Homogenous nucleation temperature, 14 9 Homoiohydric, 149, 153 Homologous, 100 Homology, 106 Homonyms, 179 Homopolymeric proteins, 102 Homoserine, 89 lactone, 89 Hormone, 127 binding protein, receptor, sensitivity, 12 7 Hour-glass timer, 131 Hour (h), 7, 12-13 However, 167 Hybridization, 100 Hybrid duplex, 10 0 Hybrids, 24 Hydraulic: conductance and resistance, 6 3 Hydro-, 124 Hydrogen ion concentration, 206, 208-209 Hydropathy plot, 100 Hydrophyte, 15 3 Hydrostatic pressure, 61 Hydroxylysine, 89 Hydroxyproline, 89

3

224 Index Hygro-, 12 4 Hygroscopic movement , 12 1 Hyphen(s), 10 , 11, 14, 166, 170 , 177 , 18 5 Hyphenation, 178 , 184 , 18 7 Hyponasty, 12 5 Hypothesis test, 30 difference between two means, 30 difference betwee n two proportions, 31 mean, 30 proportion, 31 two variances, 31 variance, 3 0 Hypoxanthine, 9 1 Hz (symbol for here), 9

Ice: deletion mutants, 14 9 encasement, 14 9 nucleating bacteria, 14 9 nucleation active bacteria, 14 9 nucleators, 14 9 IDP, 88, 137 IEF, 10 0 Illuminance, 204 Immunodetection, 10 0 IMP, 88 Impaction, 13 7 Imperative, 17 6 Imposed dormancy, 13 6 In (in botanical nomenclature) , 2 4 INA, 149 Incomplete sentence, 16 4 Indefinite articles, 16 9 Independent, 164 clause(s), 166 , 17 6 Indeterminate, 13 7 growth, 112 Index herbariorum, 2 1 Indirect object, 16 5 Induced, 121-122, 137 state, 137 Induction, 100 , 13 7 Infinitive, 17 5 Information, 18 0 Informational slide, 19 1 Infradian rhythm, 13 1 Infrared, 6 6 spectra, 89 Infraspecific taxa , 22-23 Inhibitor, 13 7 Initial, 11 3 Initiation, flower, 137 Innate dormancy, 13 6 Inosine, 91 Input signal, 12 1 Insertion, 10 0 Insertional mutagenesis, 10 0 Intensifies, 200 Interaction, 36 Intercellular freezing, 14 9 Intercept, 32

Interjections), 164 , 16 7 Intermediate-day plant, 137 Intermittent warming, 145 Internal stimulus, 121 International Bureau of Weights and Measures, 4 International Organization for Standardization, 4 International Cod e of Nomenclature fo r Cultivated Plants, 25-26 International language, 19 4 International Scientific Unions, 93 Intransitive verb, 180 Intrinsic ice nucleator, 149 Introductory or final nonrestrictive phrases, 18 6 Introductory phrases, 17 3 Intron, 100 Intrusive growth, 113 Ionic: charge, 81 effect, 155 ; (solution) relations, 56 Ions, 7 Inversion layer, 149 Irradiance, 9, 75, 210 Irregular forms, 176 Iso-electric focusing, 100 ISO Standards Handbook, 4, 15 , 17 Isocitric acid, 90 Isoleucine, 89 Isotopically labeled compounds, 82 ISPMB number, 107 Italic type, 5, 11, 15, 17, 22-23, 25, 17 8 ITP, 88 Its, it's, 180 Joule (J), 9, 12 , 14, 18 Justify the right margin, 184, 18 7 Juvenility, 13 7 Kelvin (K), 5-7, 10 , 12 a-Ketoglutaric Acid, 2-oxoglutorate, 9 0 Killing temperature, 14 9 Kilo (prefix = k), 8 , 10 Kilocalorie (kcal or Cal, obsolete), 8 6 Kilogram (kg), 5, 6, 10 Kilohm (kCi), 10 Kilopascal (kPa), 14 , 18 Kinematic viscosity, 63 Kinematics, 112 Kinesis, 12 3 Kinetic energy, 66 per amount of substance, 67 Kingdom, 22 K-jugate phyllotaxis, 11 3 Kodak pamphlet, 19 7 Kruskal-Wallis k-Sample Test, 40 Krypton-86 atom, 5 L (symbol for liter), 10, 13 , 17 Labeled compounds, 93 Labiatae, 2 2 Lamellar phase, 149

Index 22 Lamiaceae, 2 2 Language conventions with Si-unit names and symbols, 13 Language problems, 19 4 Languages, 1 Lariat, 100 Latency, 12 2 time, 122 Latent energy flux, 70 Latin, 23 square design, 34 Lawn, 100 Lay, lie, 180 LD (long day), 13 1 LDP (long-day plant), 13 7 Le Systeme International cTUnites (SI), 6c Edition, 4 Leaching requirement, 155 Leaf: area index, 117-118 area ratio, 116-11 8 conductance, 66 mass ratio, 116-118 plastochron index , 113 weight ratio, 11 7 Least squares techniques, 31 Legibility, 190-19 1 Leguminosae, 22 Length, 5, 7 Lettering, 190-19 1 Leucine, 89 Levels of authority, 4 Library, 100 Ligation, 10 0 Light, 204 break, 132, 138 growth response, 12 3 span, 13 2 trap, 12 3 Light-harvesting complex type I, 107 Like, as, 180 Line graphs, 19 1 Linear, 111 model, 33-34, 38 comparisons, 37 Lipids, 94 Liquids: in gases, 5 6 in liquids, 56 List 177 Liter (L), 4, 10, 12-13, 16 Litre (British, French spelling), 4, 13 , 16 LL (continuous light), 132 Local: control, 27 derivative, 11 2 Locomotion, 12 0 Locus, 100, 105 Logic in the English language, 163 Logistic function, 112 Long-day plant (LDP), 137 Long-short-day plant (LSDP), 138

Low temperature: exotherm, 149 injury, 14 9 Lowercase, 9-10, 13 , 23 LPI, 11 3 LR, 155 LT50, 149 LTE, 14 9 Luminous intensity, 5-7 Lux, 8, 10 Lysine, 89 m (symbol for meter), 6, 14 , 17 M (symbol for morgan), 10 1 Magnetic field strength, 9 Main effect, 3 6 Malic acid, 90 Mangroves, 155 Mann-Whitney Two-Sample Test, 40 Mannose, 90 Magneto-, 124 Marking pen, 198 Mass, 5-7, 16 communication, 181 flow, 73 Masking, 132 Material derivative, 112 Mathematical entities, 11 Matric potential, 61, 62 Maturity, 138 Maxwell, 3 May, 180-181 MejSO, 88 Mean, 27 square error, 27 Mean Comparisons, 35 Duncan's test, 37 Fisher's least significant differenc e test, 3 7 Newman-Keul's test, 37 Tukey's test, 37 Meetings presentations, 18 8 Melting point depression, 150 Median, 28 Medium, media, 181 Mega (prefix = M), 8 , 10 Megapascal (MPa), 14 Megaplasmid, 10 0 Megohm (M ) , 10 Member numbers, 106 Membership in a: plant-wide gene family, 10 6 multigene family, 10 6 Membrane: fluidity, 15 0 permeability, 15 0 Menaquinone, 8 6-Mercaptopurine, 9 1 ribonucleoside, 91 Meristem, 113, 138 Merophyte, 11 3 MES, 93

5

226 Index Mesophyte, 153 , 15 5 MESOR, 13 2 Messenger RNA , 92 Metabolic heat energy, 66 Metastable state, 150 Methionine, 89 Methods and results, 186

Meter (m), 4-5, 9-1 0

Metre (British, French spelling), 4- 5 Metre Convention, 4 Metric: ton, 10 , 13 metric system, 3 Michaelis constant, 58 , 87 Micro (prefix = u), 8, 11, 15 Micrometer (um) , 14 , 18 Micromolar (obsolete ; use micromoles/liter), 8 6 Micron (obsolete; use micrometer), 14 , 18 Midline estimating statisti c of rhythm, 132 Might, 18 1 Milli (prefix = m), 8, 10 Millimicron (obsolete), 14 Millimolar (millimoles/liter) , 8 6 Mimosaceae, 2 2 Minimum: leaf number, 13 8 survival temperature, 15 0 Minute (min), 7, 11-1 3 Miohalophyte, 15 5 MissenseDNA, 10 1 Mitochondria, 10 6 Mitochondrial DNA , RNA, 92 Mnemonic, 10 7 Mobility, 58 Mode, 28 Modifier, 17 0 Modifying: phrases, 172 words, 18 5 mol (symbol for mole), 6, 14 Molality, 1 7 Molar and molal solutions (obsolete), 14, 16 Molar (obsolete; us e moles/liter), 8 6 Molarity, 1 7 Mole, 4- 7 of photons, 14 , 17 fraction, 56, 212 Molecules, 7 Molecular: mass, 8 3 weight, 83 Monocarpic species, 13 8 Monochromatic light , 8 Monomolecular growth function, 112 Month, 7, 12 MOPS, 93 Morgan (M), 10 1 Movement, 12 0 mechanisms of 120 MSE, 27 Multigene:

families, 10 6 family, 10 1 Multiple: regression, 3 1 unit, 15 Multiplication, 10-1 1 sign, 24 factors, 1 2 (product) dot, 10 Mutation, 101 N (symbol for newton), 9 JV-Acetylglucosamine, 90 NADandNAD+, 88 NADH, 88 NADP, NADP+, and NADPH, 88 Names, 13,1 4 of units, 1 0 Nano (prefix = n), 8, 10 Nanometer (nm), 14 , 18 Nanomolar (obsolete), 8 6 Nastic movement, 123 Nasty, 123 National Agricultural Library of the USDA, 107 National Physical Laboratory, 4 National Institute of Standards an d Technology, 4- 5 National Bureau of Standards, 4 Negative, 12 4 exponents, 11-12, 15 Neither, 181 Nernst potential, 57 Net assimilation rate, 116-118 Net irradiance, 67 , 69 Nevertheless, 167 Newton (N), 6-7, 9-10 , 1 2 Nifplasmids, 10 0 Night break or interruption, 138 Nightlength, 13 8 NIST, 4 SP 811, 15 , 17 Nomenclature of: sequenced plant genes, 105 traditional genetics, 10 5 Non-osmotic volume, 63 Nonrestrictive, 173 , 17 4 phrase, 17 2 phrase or clause, 186 phrases and clauses, 177 , 18 3 phrases or clauses, 18 6 Nonsense DNA, 101 Nor, 164, 18 1 Norleucine, 89 Northern blot, 101 Noun(s),22, 164-165 , 169-171, 181, 185 in apposition, 23 Nuclear DNA and RNA, 92 Nuclear magnetic resonance, 89 Nuclear-encoded genes, 106 Nucleic acids, 94 Nucleoid, 101 'Nucleoside, a,'91

Index Nucleotide(s), 94 , 101 Nucleus, 10 1 Nuclide 12C , 13 Null-response technique , 13 8 Numbers), 4, 14 Number of photons, 75 Numeral(s), 11 to begin a sentence, 1 4 Numerical value, 4 Nutation, 12 5 Nutrient concentration i n plant tissue, 116 Nutrition, 206 , 208-209, 213 Nyctinasty, 12 5 Objective: case, 171, 185 complement, 16 5 Object(s), 164-165 , 185-186 Obligatory response, 13 9 Oersted (obsolete) , 3 Ohm( ) , 9, 12 Oligohalophyte, 15 5 One-instant mechanism, 12 4 Opaquing material, 19 8 Optical: density, 8 3 rotary disperson , 8 9 Optically activ e isomers , 8 1 Or, 164, 181 Oral: presentation, 191 , 194 report, 18 8 Order (ordo), 22 Ordinate, 18 9 Orotate, 9 1 Orotidine, 9 1 Ortho-, 12 4 Orthogonal polynomials , 38 Oscillator, 13 2 Osmoregulation, 15 5 Osmotic: adjustment, 153 , 155 coefficient, 6 3 effector, 15 5 potential, 61-6 2 potential gradient, 7 4 pressure, 61-6 2 shock, 155 stress, 156 Osmotically generate d flow, 73 Osmoticum, 15 6 Outline slide, 189 Ounce, 1 1 Overhead transparency , 19 3 Oxalacetic acid , 90 Pa (symbol for pascal), 9 Palindrome, 10 1 Palmae, 22 Papilionaceae, 2 2 PAR, 204, 213

Paraheliotropic, 15 3 Parastichy, 11 3 Parentheses, 23 , 173-174, 177 , 186 Parenthetical: interrupters, 17 7 material, 17 7 phrases, 173, 186 Partial: molar, 55 molar volume, 57 pressure, 212 pressure of gaseous species j, 66 Participles, 170 , 175, 186 Partition coefficient, 5 8 Partitioning, 7 2 Parts of speech, eight, 164 Parts per: billion, 1 4 million, 14 , 18 Pascal (Pa), 9, 12 Passive voice, 176, 186 Past: participle, 170, 175 tense, 17 5 Pause, 166, 177 PCR, 10 2 Pendulum timer, 132 Peptides, 93 Per, 10, 12 , 15, 24 Percent, 18 1 dry mass, 11 8 symbol (%), 11 Percentage, 18 1 by volume, 11 Perception, 12 1 Perennials, 13 8 Period(s), 132, 167, 174, 176-177, 185-186 Perfect, 18 3 Permeability coefficient, 5 8 Personal pronouns, 171, 185 Peta (prefix = P), 8 PFU, 10 1 PGD, 107 pH, 213 Phage, 101 Phase, 13 2 angle difference, 13 2 change, 138 response curve, 132 shift, 13 2 transition temperature, 150 Phenotype, 101, 105 Phenylalanine, 89 Phloem: export rate, 73 import rate, 74 loading, 73 mass flux, 74 pressure gradient, 74 unloading, 7 3 Phobic response, 122

227

228 Index Phobism, 12 2 Phobotaxis, 12 2 Phosphoenolpyruvic acid , 90 3-Phosphoglycerate, 9 0 6-Phosphogluconic acid , 90 Phosphoric acid residue, 89 , 92 Phosphorus, 94 Photo, 12 3 growth response, 123 oxidation, 143 , 15 0 Photoassimilate, 7 2 Photofraction, 13 2 Photograph, 19 6 Photographic techniques for creating slides, 197 Photomorphogenic radiation , 20 4 Photon(s), 7, 204 and energy flux, 207 exposure, 76 flow rate, 204 fluence, 204 fluence rate, 204 flux, 76, 204, 210 or energy flux, 208 Photoperiod, 13 2 Photoperiodic, 13 8 Photoperiodism, 13 8 Photosynthesis rates, 16 Photosynthetic irradiance, (PI), 66 , 77, 211 Photosynthetic photon flux, (PPF), 66 , 77, 211 Photosynthetically active radiation (PAR), 66, 77, 204 Photosynthetically active radiation, photon basis, 66 Phototropism, 77, 123 Phraeatophyte, 15 3 Phrase, 164 , 17 3 Phylloquinone, 89 Phyllotaxis, 11 3 Phylum, 22 Physical quantity, 3-4, 10 , 18 Physiological drought, 15 6 Phytochrome, 13 9 far-red absorbing form, red-absorbing form, and total, 77 Phytohormone, 12 7 Pi; 88 PI, 11 4 Pico (prefix = p), 8 Picomolar (pM; use pmol/L), 86 Pie charts, 191 PIPES, 93 Plagio-, 124 Plain-color (no information) slides, 18 9 Planck's constant, 6 6 Planned comparisons, 3 5 Plant: growth regulator, 12 7 hormone, 12 7 or fungal material, 21 tissues, 7 Plant-wide family, 106 Plaque forming unit, 101 Plasmid, 101

Plasmolysis, 150 Plastochron: index, 114 ratio, 114 Plastoquinone, 89 Plating, 101 Platinum, 7 Pleomorphic Fungi, 25 Ploidy, 101 Plural, 13 subject(s), 17 5 verbs, 17 5 Plurals of unit names, 10 Poaceae, 22 Poikilohydric, 153 plant, 150 Poikilotherm, 150 Pointer, 193 Poise, 3 Polar transport, 128 Polaro-, 123 Poly(A)- and Poly(A)+, 101 Polyadenylation, 101 Polycarpic species, 13 9 Polymerase, 101 chain reaction, 102 Polynucleotide, 10 2 Polyol, 156 Polysaccarides, 85 Pooled variance, 29 Population: mean, 30 proportion, 31 variance, 30 Positive, 124 Possessives, 17 7 Poster, 188 , 19 7 abstract, 196 discussion, 19 7 presentations, 19 5 Post-translational regulation, 10 2 Post-transcriptional regulation, 102 Power (watt = W), 9 ppb, 14 PPj PPi, 88 88

ppm, 14 Precede, 181 Prechilling, 139 Precision, 206 Precocious, 139 Predicate, 164 Preferred S I unit, 8, 17 Prefixes, 4, 8, 10, 170 Premature termination, 10 2 Prepared speech, 193 Present: participle, 170, 175 tense, 175 Presentation(s) 188-190 Presenting scientific data, 16 1 Pressure, 9; 62

Index 22 chamber apparatus (theory of), 53 flow, 73 flow hypothesis, 72 potential, 61-6 2 Preposition(s), 164, 171, 179-180, 18 5 Prepositional phrase, 165 Primary: event, 143 , 145 transcript, 10 2 Primer, 10 2 Principal, principle, 18 1 Printer(s), 184, 187 Probe, 102 Proceed, 18 1 Product, 10 6 Product dot, 11, 15 Projection screen, 19 0 Projectionist, 19 3 Proline, 89 Pronoun(s), 164-165, 169-17 1 Promoter, 10 2 Proof, 18 7 the final manuscript, 18 4 Proportional font(s), 185, 187 Protein structure : primary, 10 2 quarternary, 10 2 secondary, 10 2 tertiary, 10 2 Proteins, 93 Proved, proven, 18 2 Proximal, 99 Pseudogenes, 10 2 Pseudoreplications, 2 7 Pseudouridine, 91 Psychrometric constant, 6 8 Pteroic acid (pteroyl-), 8 9 Pteroylglutamic acid, 89 Public databases o f plant genes, 10 7 Publication, 188 Publish or perish, 16 1 Published results, 17 5 Pulsed-field electrophoresis, 10 2 Punctuation, 163 , 164, 166, 168, 170, 172, 176 'Purine, a,'91 'Purine nucleoside, a, ' 91 Pyridoxyl-, 89 'Pyrimidine, a,' 91 'Pyrimidine nucleoside, a,' 91 Pyroglutamic acid ; 5-oxoproline, 89 5-Pyrrolidone-2-carboxylic acid , 89 Pyruvic acid, 90 Qualitative response, 139 Quantitative response, 139 Quantity of: isotope, 59 substance, 7, 59 Quantum: of radiant energy (a quantum), 66 yield, 77

Question mark(s), 176-177 Quiescence, 139 Quinones, 95 Quotation marks, 25, 177 Quotient, 1 2 Races, 25 Radian, 5 Radiant energy, 66, 75, 203 flux, 6 9 Radiant exposure, 75 Radiation, 203, 206, 210 frost, 148 , 150 Raised period, 11 Random-amplified-polymorphic DNA, 102 Randomization, 27 Randomized Block Design, 33 Range, 28 RAPD, 102 Rate constant, 5 8 Rather, 167 Reading frame, 102 Recalcitrant seeds, 139 Receptor, 102, 121, 139 Reciprocity law in photoresponses: Bunsen-Roscoe law, 122 Reclamation, 156 Recombinant, 103 Reductive Pentose Phosphate Cycle, 90 Reflectance, 76 Reflection coefficient , 63 , 65, 67 Reflectivity, 6 7 Regnum, 22 REGR, 112 Regrowth, 143, 150 Regulation, 103 Rehearsal for presentation, 19 3 Rejuvenation, 13 9 Relative: elemental growth rate, 112 growth rate (r), 112, 116, 117, 118 humidity, 67, 205 molecular mass, 87 plastochron growth rate, 114 pronoun(s), 167, 172, 186 water content, 153 RELEL, 11 2 Repair, 143, 150 Rephasing, 132-13 3 Replication, 27 Reporter gene, 103 Represser, 103 Research results, 196 Resistance for gaseous diffusion fo r species/, 67 Respectively, 182 Response adaptation, 122 Rest, 13 9 Rest endo-dormancy, 14 6 Restriction: enzyme, 10 3 fragments, 10 3

9

230 Index -fragment-length polymorphism , 10 3 Restrictive, 17 3 phrase, 172 phrase(s) or clause(s), 186 phrases and clauses, 18 2 Retardation factor, 8 7 Retinoids, 9 5 Revernalization, 13 9 Reversal processing for technical pa n film, 200 Revolutions pe r minute, 8 6 RFLP, 103 Rhamnose, 90 Rheo-, 12 4 Rhythm splitting, 13 2 Riplasmid, 103 Ribonucleic acid, 10 3 Ribose, 9 0 Ribosomal RNA, 92 Ribosylnicotinamide, 9 2 Ribosylthimine, 9 2 Richards growt h function, 112 Right margin, 187 Ripeness-to-flower, 13 9 RNA, 88, 103 editing, 10 3 Roman, 1 5 alphabet, 5 (upright) type, 5, 11 Rosette plant, 14 0 Round brackets, 17 3 Rules for botanical nomenclature, 21 Running, 120 phase, 120 RWC, 15 3 s (symbol for second), 6 S (symbol fo r Siemens), 9 Salination, 15 6 Saline: adaptation , adjustment, sodi c soil, and stress, 156 Salinity, 15 6 threshold, 15 6 SAMPL, 10 3 Sample size, 4 1 Salt: -affected soil , 15 6 balance, 15 6 glands, 15 6 resistance, 157 tolerance, 157 SAR, 15 7 Sarcosine, 89 Saturated soi l paste, 157 Saturation: extract, 15 7 percentage, 15 7 Scales, 6 Scarification, 14 0 Science, 16 1 Scientific: paper, 161

writing, 16 3 Scion, 14 0 Scoreable marker, 10 3 Scoto-, 12 3 Scotonasty, 12 5 SDP (short-day plant), 14 0 SDS, 88 , 104 Seasonal cro p yield, 116 Second (SI unit, s), 5-7, 1 3 Second: law of thermodynamics, 46 messenger, 10 3 symbols, 1 1 level sources, 1 5 Secondary: event, 144-14 5 juvenile phase, 13 9 juvenility, 137 Sedimentation coefficient, 8 7 Sedoheptuose-7-phosphate, 9 0 Sedoheptuose 1,7-bisphosphate , 90 Seed-coat-imposed dormancy, 13 6 Segregational: analysis, 105 nomenclatures, 10 5 Seismo-, 12 3 Selectable marker, 103 Selection, 10 3 Selective amplification of microsatellites polymorphi c loci, 103 Self-inductive, 13 5 Self-sustained oscillations, 13 2 Semicolon(s), 167-168 , 176-177, 185 Semidian rhythm, 132 Sense-impression verbs, 17 1 Sensible: energy flux transfer, 69 heat energy transfer, 66 Sensitivity: of the human eye, 8 to chilling, 146 to growth regulators, 12 7 Sensory, 12 2 Sentence(s), 164 , 167 , 18 5 Sentence fragment, 164, 168 , 17 4 Sentences should not begin with numerals, 11 Sequence, 10 3 Serial comma, 176 Series, 17 6 Serine, 8 9 Sevres, France, 3, 5 Shall, 182 Short-day plant (SDP), 140 Short-long-day plant (SLOP), 14 0 Sialic Acid, 90 Siemens (S), 9-10, 1 2 Sieve-element/companion-cell complex, 73 Sigmoid growth curve, 112 Sign test, 40 Signal, 12 1 peptide, 10 3

Index 23 sequence, 10 3 transduction, 103 , 122 transmission, 122 Simple: effect, 3 7 linear regression, 31 Since, 18 0 Since, because, 18 2 Single: family, 10 6 leaf photosynthetic rate , 117 Singular: nouns , subjects), and verbs, 175 Sink, 73 Sinusoidal: curve, 13 2 rhythm, 13 3 Sit, 18 0 Skeleton photoperiod , 133 Slash, 11-12 , 15, 178 Slide(s), 188, 190-192, 197-20 0 Slide presentations, 18 9 SLDP (short-long-day plant) , 14 0 Slope, 31 Snow mold, 150 So, 164, 182 ...as, 180 -called, 18 2 Sodicsoil, 15 7 Sodicity, 15 7 Sodium: adsorption ratio, 157 dodecyl sulfate, 104 Software, 188-18 9 Soil and liquid temperatures, 207-208 Soil-plant-atmosphere continuum , 153 Solar: irradiance, 67 tracking, 123 Solids: in gases, liquids, and solids, 56 Solidus, 1 2 Solonchak soils, 15 5 Solonetz soils, 15 5 Soloth soils, 15 5 Solute: flux, 62 potential, 61 , 62 permeability, 6 2 Solution concentrations, 1 6 Source, 7 3 Southern blot, 10 4 SP 811 (NIST publication) , 4 SPAC, 15 3 Space, 5 between numerals and units, 15 to group numerals, 1 2 Spatial sensing of direction, 12 4 Special Publication (SP) 811, 4 Species, 22-23 of plant, 10 6 Specific: activity, 59

electrical conductance, 5 8 epithet, 23 growth rate, 116-11 7 heat capacity of dry air, 66 latent heat of fusion, 6 7 latent heat of vaporization, 6 7 leaf area, 116-118 leaf mass, 116, 118 rotation, 8 7 Spectral: distribution, 20 3 energies, 1 6 energy flow rate, 203 energy fluence, 204 energy fluence rate, 204 energy flux, 75, 203, 211 irradiance, 9, 75, 211 photon fluence rate, 20 4 photon flux, 76, 204, 211 photon or energy flux, 207-208 Spectrophotometric data, 83 Spell checker, 18 4 Spelled-out unit names, 11 Spliceosome, 10 4 Splicing, 10 4 Split gene, 10 4 35 S promoter, 97 Square: brackets, 24 , 173-174, 177 meter, 1 6 Squares, 11 Standard: unit, 5 "gravity", 1 4 acceleration due to gravity, 8-9 , 12-14 , 17 deviation, 28 Standard error of: estimate, 32 difference betwee n two means, 29 mean, 28 slope 32 Standards, 3 Statistical tables, 191 Steady growth, 11 4 Stefan-Boltzman: Constant, 6 8 Law, 69 Step-up, step-down, 12 4 Steradian, 5 Stereochemistry, 93 Steroids, 94 Stimuli, 12 3 Stimulus, 121, 12 3 perception, 12 1 transduction, 122 Stock, 140 Stokes, 3 Stopcodon, 10 4 Strain, 21, 14 4 Stratification, 139-14 0 Stress, 14 4

1

232 Index Strophiolar clef t or plug, 137 Strophism, 123 Style:

commas, 17 7 conventions, 1 0 manuals, 163 , 165 Subcooling, 15 0 Subject, 164-165, 173, 175, 185-186 complement, 186 Subjective: complement, 165 and objective cases, 171 Subjective day or night, 13 3 Subjunctive mood, 18 3 Subordinate: clause, 16 8 phrase, 185 Subordinating conjunction, 167, 185 Subspecies, 22 Substrate, 206, 209, 212 Subtraction library, 104 Successor apical cell, 113 Succinic acid, 90 Succulence, 157 Succulents, 15 3 Suffixes, 17 0 Sutfate salinity, 157 Summer dormancy, 14 0 Sunscald, 15 0 Supercooling, 15 0 Superoxide dismutases, 106 Superscripts (an d SI units), 11 Supplementary units, 5 Suppression, 10 4 Surface tension, 63 Susception, 12 1 Swedberg (not SI), 86 Symbol(s) 13-14, 17 Symbols for the monomeric units, 85 Symplastic growth, 11 4 Symptoms of injury, 144 , 146 Synchronizer, 13 3 Synonym, 24 t (symbol for metric ton), 13 T50, 151 T-region of Ti plasmid, 104 Tables, 183, 191 Tactic orientation, 12 2 TAPS, 93 Tau, 131 Taxis, 122 Taxon, 22, 24 Taxonomic groups, 2 2 TDP, 88 TEAE-cellulose, 88

Technical writing, 172-173, 176 Teleomorph, 2 5 Telomere, 10 4 TEMED, 93 Temperature, 5 , 7, 67, 205-206, 211

dewpoint, 205

dry bulb, 205 gradient, 1 6 -sensitive mutation , 10 4

wet-bulb, 205 Template, 104 Temporal sensing of direction, 124 Tense, 175 , 186 Tera (prefix = T), 8, 10 TES, 93 Test of hypothesis, 30 Tetrapyrroles, 95 Text, 190 slide, 189-190 Thawing, 151 Than, 18 2 That, 172-174, 182, 186

The International Syste m of Units (SI Units), 3-2 0 Then, 18 2 Theory of minimum artical cell volume, 15 1 Thermal conductivit y coefficient o f region j, 66 Thermo-, 12 4 Thermoavoidance, 15 1 Thermocouple hygrometers, 5 3 Thermodynamic temperature, 5- 7 Thermoperiodism, 14 0 Thermophile, thermophilic , and thermophily, 15 1 Thermostability an d thermotolerance, 15 1 Thickness of: air boundary layer, 6 8 unstirred layer, 63 Thigmo-, 12 3 Thiohypoxanthine, 9 1 6-Thioinosine, 9 1 Thiouridine, 92 Third person, 17 1 Threonine, 89 Thus, 16 7 Thus, thusly, 18 3 Thymidine, 9 2 Thymine, 91 Ti plasmid, 10 4 Time, 5, 7 Times earth's gravity (g n), 87 Tissue sample, 16 Title(s), 183, 18 9 TK50,151 TMP, 88 Tmax and Tmin, 151 Tocopherol, 89 Tocopherolquinone, 89 Tocopherols, 9 5 Tolerance, 144 Tonic effect, 12 2 Tonne, 1 3 Topotaxis, 12 2 Torsion, 12 1 Toward, towards, 18 3 Tranpiration or condensation, 67 Trans, 104 Transcribed, 10 4

Index 23 Transcript and transcription, 10 4 Transduction, 104 chain, 12 2 Transfer RNA, 92 Transformation, 10 4 Transient: cycle, 133 gene expression, 10 4 Transit piptide, 10 5 Transitive verb, 176, 180 Translation, 10 5 Translocatable hardines s promotor, 151 Translocation, 72 profile, 7 3 speed, 74 Transmittance, 76 Transon, 105 Transport number, 58 Transposable elements , 98 Transposition, 10 5 Transposon, 10 5 Transversal, 12 4 Traumato-, 12 4 Treatments, 3 9 Tricine, 93 Triple point of water, 7 Tris, 88, 93 Tropism, 12 3 Tropistic movement, 12 3 True halophyte, 155 Tryptophan, 89 TTP, 8 8 Tumbling, 120 phase, 12 0 Turbulent air, 67 Turgor movement, 121 Twintron, 10 5 Two-instant mechanism, 12 4 Two variances, 3 1 Type size, 196 Typefaces, 19 1 Tyrosine, 89 u (symbol for unified atomic mass unit), 9, 13-14, 17 Ubiquinone, 89 UDP, UDP-Glc, UDP-GalNAc, UDP-Gal, UDPGlcUA, UDP-GlcNAc, and UDP-Xyl, 88 Ultradian: oscillations, 13 1 rhythm, 133 Ultraviolet, 67, 89 Umbelliferae, 2 2 UMP, 88 Undercooling, 15 0 Underlining, 11 , 15, 22-23, 178 Unfamiliar names, 24 Unified atomi c mass unit (u), 8-9, 12-14 , 17 Unique, 183 Unit, 5 leaf rate, 117 name(s), 10-11 , 14

symbol(s), 10-1 1 Units: used with the SI but not officially part of SI, 13 of concentration, 86 Universal gas constant, 6 7 Unnecessary words, 178, 186 Uppercase, 13 , 25 Upstream, 105 Uracil, 91 Undine, 92 Usage, 1, 163, 165-167 UTP, 88 V(symbol for volume, electric potential), 9 V(symbol for volt), 9 Valine, 89 Vapor density deficit, 15 3 Vapor pressure: leaf and air, 67 deficit, 15 3 Variance, 28 components, 38 Varieties, 22, 25 Vector, 10 5 Velocity, 58 wind speed, 67 Verb(s), 164-165, 170, 173, 175, 185-186 tense, 175 Vernacular name, 25 Vernalin, 140 Vernalization, 140 Viability, 144, 151 test, 14 4 Viable, 140 Viewgraph, 188 Viscosity, 63 Visual browning, 151 Vitamin: B6, 95 D, 95 Volt (V), 9 Volta, 12 Volume, 5, 7, 9, 16 flux, 62 modulus of elasticity, 63 Volumetric heat capacity, 66 VPD, 15 3 W (symbol for watt), 9 Water: deficit, 15 3 evaporation site, 66 potential 11 , 47, 62 potential in the vapor state, 50 potential of aqueous solutions, 53 status, 154 stress, 15 3 use efficiency, 15 4 vapor, 67 Water vapor, 67 deficit, 20 5

3

234 Index density, 20 5 Wor Watering, 205, 208 , 21 2 Worl Watt (W), 7 , 9, 12 Writin Wave lengths, 5 , 8, 68, 76 WUE, Wave number, 76 Week, 7, 1 2 Xanthine Weight, 6 Xanthosine Were, 18 3 Xeromorphy Western blot, 105 Xerophily Which, 172 , 174 , 182 , 18 6 Xerophyte Which hunt, 17 2 Xylose White frost, 14 8 Xylulose-5-phosphate Who, 173 , 182 , 18 6 Who, whom, 173 , 18 2 YAC Wilcoxon's Signe d Rank Test, 40 Year Will, 18 2 Yeas Winter: Yoct annuals, 14 0 Yott chilling, 15 1 injury, 14 6 Zeitgeber Wish, 18 3 Zept Word processing, 184 , 18 7 Zett Words with special problems, 17 9

k (W), 9 d Directory, 2 1 g conventions, 16 3 154 , 91 , 92 , 154 , 154 , 154 , 15 7 , 90 ,9 0 , 105 , 7, 12 t artificial chromosome, 10 5 o (prefix = y), 8 a (prefix = Y), 8 , 13 3 o (prefix = z), 8 a (prefix = Z), 8