Some effects of water stress and environment on soybean plants : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Botany at Massey University

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Copyright is owned by the Author of the thesis. Permission is given for

a copy to be downloaded by an individual for the purpose of research and

private study only. The thesis may not be reproduced elsewhere without

the permission of the Author.

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S OME EFF ECTS OF WA TER STRESS AND E NVIRONM ENT ON S OYBEA N PLA NT3

A t h e s i s pre s e n t e d in partial ful fi l ment o f the r e quirements for the degre e o f

Doc tor o f Phi l osophy i n Botany

at

Mas s e y University

MICHAEL FLETC HER BE ARDSELL

1970

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ABSTRACT

Al though a great deal of research has been c arr i e d o�t on the e ffe c t s of wa ter s tress o n plant proce sse s , t h e i n f luence o f environmental c ondi t i ons on plant response t o wat e r s t ress has r e c e ive d compara t ively l ittle a t t e n t i on . In t h i s s tudy the rates o f

co2

exchange and transpi ration and the leaf wat e r s tatus o f whole s oybeen plants ( Glyc i ne max ( L . ) Merr . c v . Meri t ) were measur e d under c ontras t i ng s e t s o f e nvironmental c ondi t i ons when

( a ) the plants were maintaine d under c ond i t i ons o f ade qua t e s oi l wat e r supply .

( b ) wat e r s tress was i mpose d by wi thholding wat er and, ( c ) when wat e r stress was impos e d and then r e l i eved

by r e wa t e r i ng .

Light i n t e ns i ty and quality , atmospheric

co2

c oncantrati on , w i n d speed and daylength were all c ons tant ; the be tween

treat me n t variab l e s were a i r t e mperature and vapour pressure d e fi c i t ( VPD ) . P lant s were grown under one of four environ

mental t reatme n t s in a growth cab i n e t and the experiments carried out unde r very s imilar c ondi t i ons in a plant chambe r w i th fac i l i t ie s for measuring

co2

exchange and t ranspi rat i on . D e ta i ls o f thi s e quipment are give n .

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Unde r c on d i ti ons of a d e qua te s o i l wa te r suppl y ra te s o f pho tosyn th e s i s were l ower under l ow ^VPD than under h i gh

VPD c ondi ti o ns a t the same te mpera ture . The e f fe c t was p arti c ularly marke d at l ow te mpera ture (22.5°C). Be tw e e n

tre a tment di f f e renc es i n pho tosyn the tic rate appeared to be mai nly a ttr i buta b le to di fferenc e s i n the magni tude o f

the mes ophy ll r e s i s tanc e to co2 trans fer . Transpira ti on ra te s were large ly d e ter mine d by the VPD , plants unde r h i gh

VPD tre atme n ts having the h i gher rate s . A t l o w VPD

temperature had l i ttle e f fec t on the rate of tran spi ra ti on , but a t high ^VPD pla n ts under low tempera ture had l cwer r a te s o f transpirati on than plan ts under h i gh temperature (27.5°C).

Poss i b l e me chanisms whereby l ow te mperatures may reduce transpirati on u nder cond i ti ons of h i g h ^{V P D}are dis cusse d .

When wa te r s tre ss was i mposed the ra tes o f pho tosynth e s i s and transp ir ation de clined i n parall e l under a l l tre atmen t s a t s o i l m o i s ture te ns i ons i n exc ess o f _0.2 a tm . Thi s sugges te d tha t b o th plan t processes were sub j e c t to a c ommon c on tr ol l i ng mechanism , probably s toma tal di ffus i on re s i s tanc e . A t s o i l moi s ture tensi ons b e low _0.2 a tm . the rate s o f pho t osynthe s i s and tr �ns pirati on were i n dependent o f the s o i l moi s ture

s ta tus . Be twe e n _0.2 and _0.4 a tm . tens i on they appeare d to be de te rmine d by plant, soil and a tmosphe ri c fac tors . The r e l a ti ve ra te s o f pho tosynthesis and tra nspira ti on were r e duc e d to a

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g r e a t e r e x t en t a t any ten s i on b e t w e en 0.2 ^{an d} Oo4 a t m.un d e r h i gh VPD than un d er l ow VPD c ond i t i ons . Above _0.4 a t m . s o i l m o i s t ur e t en s i on t he r a t e s o f photv syn the s i s an1 t ran s p i ra t i on b e c am e in d ep en den t o f t h e a t mosph e r i c c on d i t i ons an d i t i6 su g g e s t e d t ha t

(

^transpirati on was l i m i t e d c h i e fly by t h e r a t e o f m ove ment o f w a t er in t o t h e r o o t zone fr o� the surr oun d ing s oil .

) (

Phot osyn t h e si s may have been l i m i ted by dir e c t e f f e c t s o f d e hy dra t i on on the b i o c h e m i cal compon en t s o f the pr o c e s s a t t h e s e s e v e r e s tr e s s l e ve l s .; I t was thus possibl e t o di s t inguish thr e e s tage s i n the d e v e l opment o f wat er s tr e s s , t h e s i gn i fi c an c e and pos s i b l e gen era l a p pl i c a t i on o f wh i c h a r e d i s c us s e d .

Un d er h i gh t e mpera t ur e/h i gh VPD � on d i t i ons t h e r a t e s _of ph o t o syn t h e s i s an d tran spira t i on r e c over e d s i mul tan e ou s ly and

to a v e ry s i m il ar e xt en t when str e s s was r e l i e ve d by r e w a t e r i n g , t h e d e gr e e o f r e c ov ery b e i� g inver s e ly p ropor t i onal t o t h e s o iJ m o i s t ur e tens i on a t the t i me vf r e w a t erin g . P os s ibl e c au s es o f t h e f a i l ur e o f t h e rat e s o f phot osyn the s i s an d trans p i ra t i on t o r e c ov e r t o t he i r o r i g inal pre s tr e s s e d val u e s are d i s c u s s e d .

The s e r e su l t s ar e d i s c uss e d in r e l a t i on to th e f in d in g s o f o ther worke rs, an d sugge s t i ons f or fur t h e r r e s e ar c h i n t h i s fi e ld made .

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ACKNOWLEDGE?•lENTS

I wou l d l ik e t o t han k Pr o f e s s or R.G . Thomas (M a s sey Un i ver s i ty) f or h i s gui dance an d in t ere s t , an d expr e s s my gra t e ful appr ec i a t i on o f th e enccur a gem ent and h e l p fu l cr i t ic i s m I r ec e iv e d fr om Dr . K . J . M i tc h e l l (P l an t P hys i ol ogy D i v i s i on , D . S . I . R .). I a m a ls o inde b t e d t o many members o f t h e D .S . I. R. s t a f f f or use ful d i sc us s i on s .

I wi s h t o t hank t h e techn ic a l s taf f o f P lan t P hy s i ol ogy Di vi s i on for t heir s ki l l e d a s s i s t anc e ,

par t ic ular ly Mr . J. S . Talbo t wh o se e l ec tr on ic exper t is e was inva luable .

I a m e sp ec ia l ly gra t e fu l t o my wife , Car o l , for her en d l es s enc o ur a g e men t and un ders t a n d in g: she has a unique kn o w l e d ge of an a s pec t of this inve s t i ga t i on n ot r e p or te d i n t h e s e page s .

F in a l ly I t hank _Mr. P.H . Menal d a f or h i s pho t o graphic w ork, an d Mr s . M argare t Br o gden f or typ ing t hi s t h e s i s .

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TABLE OF CONTE NTS

A ck now le dgeme n t s • • • • • • •• • •

Li s t of Figure s • • • • •• • • • •

CHAPTER 1 I NTR ODUCTI ON

I ntrod� c ti o n to the pre se nt s tu dy Review of the li ter a ture •• ••

CHAPTER 2 I.

II.

III.

IV.

MATER I ALS A N D MET HODS

O u t li ne of e xpe rimen tal de si gn C on di ti ons i n the grow th cabi ne t

and plan t chambe r •• •• • •

P re parati on of pl ants i mme di a tely p ri or t o e xpe rime n t • • ••

Eq uip me n t use d f or me asuri ng

co2

e xc hange and tra nspir a ti on ^{• •} V. E xpe rime n tal p roce dure s •• • •

VI. C a l c u l a ti on of re sul t s • • • •

• •

••

• •

••

• •

••

• •

CHAPTER 3 EFFECTS OF TEMPERATU RE A N D VAPOU R P RESSURE DEF I C IT ON THE C

02

^EXCHANGE

A N D T RANSP I RATION RATES OF SOYBEAN In troduc ti on ••

Me thods • •

Re sul t s ^••

Di scussi on

• •

• • • • • • • •

CHAPTER

4

^THE E FFE C T OF WATER O N THE CO

EXCHANGE A ND TRANS P I RATI ON RA

�

^{ES OF}

S OY BEAN _PLANTS UNDE R C ONTRAST I NG ENVIR ONHENTAL CONDITI ONS

I n troduc ti on • •

Me thods • •

Re sul t s ••

Di sc us si o n

• •

• • • • • • • •

P age

Vo viii.

1 ^•

4.

20

^•

2 1 .

23 ^•

24.

33 ^• 37 ^•

76 . 77 . 1 1 6 . 79.

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C HAPTER 5 RESP ONSE OF SOYBEA N PLA NTS TO REWA TE RING FOLLO�ING WA TER S TRESS UNDER TWO CONTRA S TING SETS OF ENVIRONMENTA L CONDIT I ONS

I ntroduc ti on • • • • • • • 0 • • • •

M e thods ^{• •} • • • • • • • • • • • •

R e sul t s • • • • • • • • • • • • • •

Di scussi on • • • • • • • • • • • •

C HAPTER 6 S ONE ASPE C TS OF LEU' STRUCTURE �IH ICH M A Y AFFE C T RATES OF GASEOUS EXCHA NGE I nt r o d1J. c ti on • • • • • • • • • • • •

M e thod.s • • . . ^{• •} ^{• •} ^{• •} ^{• •} ^{• •} R esul t s • • • • • • • • • • • • • •

Di s c ussi on • • • • • • • • • • • •

CHAPTER 7 CONCLUSI ONS • • • • • • • •

APPEND ICES

App e ndix 1 . P re li mi nary t e s t s wi t h v ari ous p o t ti ng mix tur e s • • • •

App e n dix 2 . Ev olu ti on of co2 a n d ev ap ora ti on of wa t e r fr om p o t s • • • •

App e n dix 3 . }! e asure m en t of p lant w a t e r s tress App e n dix

4.

M e asurement of l e af &r3 a a nd

d e t e rmination of t he leaf area- leaf dry w eigh t r e l a tionship s of plan ts t:; r own under the f our trea t me nts • • • • • •

App e ndix 5 . Cali b ra ti on of th e co2- a ddi ti on sy s t e m • • • • • • • •

App e n dix 6 . Di s tributi on of dry ma t t e r i n the p lant • • • • • • • •

App e n dix 7 . Detail p l ot s of Fi gures 4-4, 4- 1 0 and 4- 1 1 • • • • • •

REFERENCES • • • • • • • • • • • • • •

P age

1 3 4 . 1 3 7 ^• 1 3 8 . 1 50 ^•

1 56 . 1 5 8 . 1 6 1 . 1 70 ^• 1 73 .

1 90 ^•

1 93 ^• 1 96 .

205 ^•

2 1 2 . 214 .

2 1 6 . 223 .

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Fi gure 2-1

LIST 01'' FIGURES

Gas flow c i r c ui t diagram o f the plant

?

02 e x c hange and transpira t i on measur- 1ng e quipme�t ^{• •} ^{• •} ^{• •} ^{• •} ^••

3 -1 M e an maxim�m rates of phot osynth e s is ( m g C O?/dm /

�

r ) and transpirat :on ( gm wa�e r/dm /hr ) under the four

3 -2

3 -3

4-1 4-2

treatme nt s ^{• •} ^{• •} ^{• •} • • • •

E ffe c t of atmospheric VPD on

�

^{he rate}

of transpira t i on ( gm wa ter/drn /hr ) ^{• •} Re l a t i onship be tween the mea n max i �um ra t e s o f pho t osynthe s i s ( mg C02/d m /hr ) a n d transpir a t i on ( gm water/dm /hr ) Re pre senta t i ve time c ours e s o f pho t o

synthe s i s under the four trea tments R e pr e s e nt a t i ve time c ours e s of transpirat i on und er the four

treatments ^{• •} ^{• •} ^{• •} ^{• •} ^{• •} 4-3 Change s in R

�

C ( %) , transpiration rate

(gm wat e r/urn /hr ) a nd s o �l moi sture t e nsi on ( a tm . ) dur ing the c ourse o f a three day experiment under HT/LH 4-4

4-5

4-6

c ondi t i ons ^{• •} ^{• •} ^{• •} ^{• •} ^••

R e l a t i onships be twee� rat e s o f photo

synth e s i s (mg C02/dm /hr ) �nd

transpi rati o n ( gm wat e r/dm /hr ) be twe en 0 and 0 . 4 a t m . soil m o i s ture tens i on o f plants grown under t h e f our treatments E f fe c t of soil moisture t e ns i on .on2 the r a t e of transpi ra t i on ( gm wat e r jdm /hr ) o f plants under the f our treatmen t s E ffe c t o f s o i l mois ture tens i on o � t he ra t e o f pho t osynthesis (mg C02/dm /hr ) o f plant s under the f our treatments 4-7 E f fe c t o f s o i l mois ture t e ns i on on the

r e l a t ive transpira tion rat e s of plants

Page

28.

86 .

93 .

95 .

under t he · four trea tme nt s . . ^{• •} ^{• •} _99.

vi i i .

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Figure 4-8

4-9 4- 1 0

4- 1 1

4- 1 2

5-1

5-2

E ffe c t of soil moi s t ure t ens ion on the rela tive rates of phot osynthesi s o f plants under the four trea t ments ^{• •} E f f e c t o f soil mois ture t ens ion on the RWC of plants under the f our treatments Relati onships b e t we e n RWC

�

nd rate o f transpi r a t i on ( gm wat e r/dm /hr) o f plants under the four trea tments ^{• •} ^{• •} Rel a t i onships betwe e n RWC2and rate of phot osynthesis ( mg C02/dm /hr ) of plants under the four trea tments ^{• •} ^{• •} R e l a t i onsh i p between relat ive rate s of phot osynthe s i s and transpirat i on of plants under the four treatments ^••

Time c ourses o f rewat e r i ng experiments under HT/LH condi t i ons ^{• •} ^•• ^••

T i me courses of r e wa t ering expe riments und e r LT/HH c ond i t i ons ^{• •} ^{• •} ^{• •} 5-3 Dependence o f the rec overy of photo

synthe t i c and tr�nspira t i on rat e s follow

i ng rewater i ng on the soi l mois ture tensi on ( S MT) at the t ime of rewatering under HT/LH

A1- 1 A3- 1 A 4- 1

A 4-2

A 7- 1 A7-2 A 7-3

c on d i t ions • • • • • • • • • •

S o i l mois ture c harac t e ri s t i c curve for the 1 : 1 pum i c e -peat mixture ^{• •} ^{• •} ^{• •}

Change i n fresh weight w i t h t ime o f float ing d i s c s of s oybean leafl e t s

Re l a t i onship b e twe e n t rue leaf area and the sum o f leaflet length and maximum wi dth for the whole plant ₍2 LW ) ^{• •} ^{• •} ^{• •}

Rel a t i onshi ps be twe e n l e a f area and leaf dry we i gh t of plants grown under the four t r e a tments

D e tail plots F i g _.. 4-4 De tail plots F i g . 4- 1 0 D e tail plots Fi g . 4- 1 1

• •

o f the

• •

of the

• •

of the

• •

• • • • • • • •

relati onships given i n

• • . . ^{• •} ^{• •}

rela t i onships given in

. _.. • • • • . , .

rela t i onships gi ven i n

• • • • • • • •

ix . Page

1 01 . 1 04 .

1 07.

1 09 .

1 13 .

1 �·1 ^c 1!�3 .

1 48.

1 92 . 1 99 .

207 .

2 1 0 . 2 1 8 . 220 ^• 222 ^•