carbon dioxide enrichment and temperature effects on cotton

8/10/2019 Carbon Dioxide Enrichment and Temperature Effects on Cotton

1/11

E L S E V I E R

Field Crops Research 41 (1995) 13-23

F i e l d

C r o p s

R e s e a r c h

C a r b o n d i o x i d e e n r i c h m e n t a n d t e m p e r a t u r e e f f e c t s o n c o t t o n

c a n o p y p h o t o s y n t h e s i s t ra n s p ir a ti on a n d w a t e r - u s e e f f i c i e n c y 1

V . R . R e d d y a K . R . R e d d y b H . F . H o d g e s b .

a US DA :ARS Sys t em s Res ear ch L abor a tor y , Be l t s v i l le , MD 20705 , USA

b Dep ar tmen t o f P lan t an d So i l Sci ences , Mis s i s s ipp i S ta t e U niver si ty , Mis s i s s ipp i S ta te , M S 39762 , USA

Received 20 December 1993; accepted 7 November 1994

A b s t r a c t

Th e o b j e c t i v e s o f th i s s t u d y w e re t o e v a lu a t e e ff e c t s o f a m b ie n t a n d d o u b le a m b ie n t [ CO 2 ] a t a r a n g e o f g ro w in g t e m p e ra tu re s

o n p h o to sy n th e s i s , r e sp i r a t i o n , t r a n sp i r a t i o n , w a te r -u se e f f i c i e n c y a n d d ry m a t t e r a c c u m u la t i o n o f c o t t o n p l a n t s (G o ssy p iu m

h i r s u t u m L. , c v . D PL 5 0 ) . In Ex p e r im e n t I , p l a n t s w e re g ro w n o u td o o rs u n t i J f i r s t b lo o m , t h e n t r a n s fe r re d i n to n a tu ra l l y l i t

g ro w th c h a m b e rs a n d g ro w n fo r 2 2 d a y s a t 3 0 /1 8 C w i th f i v e CO 2 c o n c e n t ra t io n s v a ry in g f ro m 3 5 0 to 9 0 0 /x l 1 -1 . In Ex p e r im e n t

I I , a i r t em p e r a t u r es w e r e m a i n t a i n e d a t 2 0 / 1 2 , 2 5 / 1 7 , 3 0 / 2 2 , a n d 3 5 / 2 7 C d a y / n i g h t d u r i n g a 7 0 - d a y e x p e r i m e n t a l p e r i o d w i th

[ C O z ] o f 3 5 0 a n d 7 0 0 / x l l - l a t e a c h te m p e r a tu r e . P h o t o s y n t h es i s i n c r e a s ed w i t h [ C O 2 ] f r o m 3 5 0 t o 7 0 0 / z l 1 -~ a n d w i t h

t e m p e r a tu r e . P l a n ts g r o w n a t 3 5 / 2 7 C p r o d u c e d f e w e r b o l l s d u e t o a b s c i s s i o n c o m p a r e d w i t h p l a n t s g r o w n a t o p t i m u m t e m p e r -

a tu re s (3 0 /2 0 C ) . A t h ig h e r [CO 2 ] , w a t e r -u se e f f ic i e n c y i n c re a se d a t a l l t e m p e ra tu re s d u e m a in ly t o i n c re a se d c a n o p y p h o to -

sy n th e s i s b u t a l so t o m o re l im i t e d e x t e n t to r e d u c e d c a n o p y t r a n sp i r a t i o n . In c re a se d p h o to sy n th e s i s a t h ig h e r [CO 2 ] r e su l t e d i n

g re a t e r d ry m a t t e r a c c u m u la t i o n a t a ll te m p e ra tu re s e x c e p t a t 2 0 /1 2 C . Re sp i ra t i o n i n c re a se d a s d ry m a t t e r a n d t e m p e ra tu re

in c re a se d . P l a n t s g ro w n a t h ig h e r [CO 2 ] h a d l e ss r e sp i r a t i o n p e r u n i t d ry m a t t e r b u t m o re p e r u n i t a r e a . Th e se r e su l t s i n d i c a t e

th a t fu tu re i n c re a se s i n [CO 2 ] a re l i k e ly t o b e n e f it c o t to n p ro d u c t io n b y i n c re a s in g c a rb o n a ss im i l a t i o n u n d e r t e m p e ra tu re s

fa v o ra b l e fo r c o t t o n g ro w th . R e d u c e d f ru i t w e ig h t s a t h ig h e r t e m p e ra tu re s i n d i c a t e p o t e n t i a l n e g a t i v e e f f e c t s o n p ro d u c t io n i f a i r

t e m p e ra tu re s i n c re a se a s p ro j e c t e d i n a h ig h -CO 2 w o r ld .

K e y w o r d s :

Atmospheric CO2;

Gos s yp ium;

Photosyn thesis; Tem perature; Transpiration; W ater-use efficiency

1 I n t r o d u c t i o n

T h e g l o b a l a t m o s p h e r i c c a r b o n d i o x i d e c o n c e n t r a -

t i o n [ C O 2 ] h a s i n c r e a s e d b y 3 0 % s i n c e t h e i n d u s t r i a l

r e v o l u t i o n , a n d t h e c o n t i n u o u s m e a s u r e m e n t o f [ C O 2 ]

a t M a u n a L o a , H a w a i i , d u r i n g a r e c e n t 3 2 - y p e r i o d

* Corresp onding author.

Contribution from the D epartment of Plant and Soil Sciences,

Mississippi State University as paper no. J8301, and the US DA-AR S

Crop Simulation Research Unit , Crop Science Research Laboratory,

M ississippi State, MS.

0378-42 90/95/ 9.50 1995 Elsevier Science B.V . All rights reserved

S S D 1 0 3 7 8 - 4 2 9 0 9 4 ) 0 0 1 0 4 - 9

i n d i c a t e d a 1 2 % i n c r e a s e in t h e a v e r a g e a n n u a l c o n c e n -

t r a ti o n ( K e e l i n g a n d W h o r t , 1 99 1 ) . C u r r e n t l y , a t m o s -

p h e r i c [ C O 2 ] i s a b o v e 3 5 2 / ~ 1 1 - ~ a n d f u r t h e r i n c r e a s e s

a r e e x p e c t e d t o r e s u l t in 6 0 0 / xl 1 - 1 C O a s o m e t i m e

b e t w e e n 2 0 3 0 a n d 2 0 7 0 ( S c h n e i d e r , 1 9 8 9 ) . C o n t i n u -

i n g i n c r e a s e s i n [ C O 2 ] a n d o t h e r ' g r e e n h o u s e ' g a s e s

m a y c a u s e a s m u c h a s 3 to 6 C r i s e i n a v e r a g e g l o b a l

a t m o s p h e r i c t e m p e r a t u r e d u e t o d o u b l i n g o f p r e s e n t d a y

[ C O 2 ] ( G r o t c h , 1 9 8 8; A d a m s e t a l ., 1 9 9 0 ) .

T h e p r i m a r y e f fe c t o f e le v a t e d [ C O 2 ] o n w e l l -

w a t e r e d p l a n t s i s a n i n c r e a s e i n n e t p h o t o s y n t h e s i s


2/11

14 V .R . R e d d y e t al . / F i e l d C r o p s R e s e a r c h 4 1 1 9 9 5 ) 1 3 - 2 3

( Jones e t a l . , 1984; Baker e t a l . , 1990) . Inc reased

[ C O 2 ] a l s o c a u s e s p a r t i a l s t o ma ta l c l o s u r e , a n d

in c r e a s e d s t o m a ta l r e s is t a n c e r e s u l t in g i n r e d u c e d t r a n -

s p i r a t i o n p e r u n i t l e a f a re a ( J o n e s e t a l ., 1 9 8 5 ) w h ic h

m a y in c r e a s e l e a f t e mp e r a tu r e ( I d s o e t al ., 1 9 8 7 ) . T h i s

i n d i r e c t e f f e c t o f [ C O 2 ] o n c a n o p y t e mp e r a tu r e , in

a d d i t i o n t o a n y g e n e r a l r i s e in a i r t e mp e r a tu r e ( G r o t c h ,

1 9 8 8 ; A d a m s e t a l ., 1 9 9 0 ) , w i l l h a v e s i g n i f i c a n t e f f e c t s

o n p r o d u c t i v i t y o f a g r i c u l t u r a l c r o p s ( R e d d y e t a l . ,

1 9 9 2 b ; H o d g e s e t a l. , 1 9 9 3 ) .

T h e p o s i t i v e s h o r t - t e r m e f f e c t s o f C O z o n g r o w t h

a n d p r o d u c t i v i t y o f c ro p s h a v e b e e n w e l l d o c u m e n t e d

b y t h e r e v i e w s o f K i m b a l l ( 1 9 8 3 ) , C u r e a n d A c o c k

( 1 9 8 6 ) , a n d N e w to n ( 1 9 91 ); h o w e v e r , s e v e r a l a s p e c t s

o f e f f e c t s o f e l e v a t e d C O 2 a n d t e m p e r a tu r e o n p r o d u c -

t i v i t y o f c r o p p l a n t s a r e n o t y e t c l e a r ( G i f f o r d , 1 9 9 2 ) .

S o c i a s e t a l. ( 1 9 9 3 ) r e p o r t e d t h a t l o n g - t e r m e x p o s u r e

to h ig h [ C O 2 ] c a u s e d

Phaseolus vulgaris

L. p lan ts to

h a v e l o w e r r a t e s o f p h o to s y n th e s i s t h a n c o n t r o l p l a n ts .

P l a n t s g r o w n in h ig h [ C O 2 ] w e r e l e s s s e n s i t i v e t o l o w

o x y g e n c o n c e n t r a t i o n s a n d , a l t h o u g h t h e y h a d s imi l a r

a m o u n t s o f r i b u l o s e - l ,5 - b i p h o s p h a t e c a r b o x y l a s e /

o x y g e n a s e , s o m e o f i t r e m a i n e d u n c a r b a m y l a t e d a n d

th u s i dl e . I d s o a n d K im b a l l ( 1 9 9 3 ) o n t h e o th e r h an d ,

r e p o r t e d t h a t d o u b l i n g t h e [ C O 2 ] f r o m 3 6 0 t o 7 2 0 / z l

1 1 i n c r e a s e d n e t p h o to s y n th e s i s b y a f a c to r o f tw o a n d

d e c r e a s e d r e s p i r a t io n b y 5 0 i n tw o tr e e s p e c i e s g r o w n

f o r 2 a n d 4 y . C u r e a n d A c o c k ( 1 9 8 6 ) f a i l e d t o fi n d

r e p o r t s a b o u t i n t e r a c t i n g e f f e c t s o f t e mp e r a tu r e a n d

C O 2 o n s e e d y i e ld i n t h e i r s u r v e y o f e ig h t m a jo r c r o p s

a n d t h e y f o u n d o n l y t h r ee s t u d i es o f C O 2 - t e m p e r a t u r e

in t e r a c t i o n s o n b io ma s s p r o d u c t i o n . Mo r e r e c e n t l y ,

B a k e r a n d A l l e n ( 1 9 9 4 ) a l s o p o in t e d o u t t h e l a c k o f

i n f o r ma t io n o n t h e i n t e r a c t iv e e f f e c ts o f [ C O 2 ] a n d

t e mp e r a tu r e w h i l e n o t i n g t h a t e x i s t i n g k n o w le d g e i n d i -

c a t e s t h a t r e s p o n s e s a r e s p e c i e s d e p e n d e n t . T h e y s u g -

g e s t e d t h a t mo r e r e s e a r c h i s n e e d e d t o d e t e r min e p l a n t

r e s p o n s e s t o i n t e r a c t iv e e f f e c t s o f [ C O 2 ] a n d o th e r

e n v i r o n me n ta l v a r i a b l e s .

I n r e c e n t st u d i e s, g r o w th a n d d e v e lo p m e n ta l r at e s o f

c o t t o n w e r e c h a r a c t e r i z e d a t a r a n g e o f t e mp e r a tu r e s

u n d e r a mb ie n t [ C O 2 ] ( R e d d y e t a l ., 1 9 9 1 b , 1 9 9 2 a ) .

T h e y f o u n d t h a t f r u i ti n g o f w e l l - w a t e r e d c o t t o n p l a n t s

i s s e n s i t i v e t o 3 5 a n d 4 0 C ( d a y t ime ) t e mp e r a tu r e s .

P l a n t s g r o w n a t 3 5 C p r o d u c e d o n ly 4 a s mu c h f r u i t

a s p l a n t s g r o w n a t 3 0 C , a n d p l a n t s g r o w n a t 4 0 C

p r o d u c e d n o f r u i t . T h e y a l s o f o u n d t h a t t e mp e r a tu r e

s e n s i t i v i ty o f f ru i t i n g w a s s imi l a r a mo n g s e v e r a l u p l a n d

c o t t o n ( G o s s y p i u m

hirsutum

L . ) c u l t i v a r s w h i l e p ima

c o t t o n

G. barbadense

L . ) w a s e v e n m o r e s e n s i t i v e t o

h ig h t e mp e r a tu r e t h a n u p l a n d c u l t i v a r s ( R e d d y e t a l . ,

1 9 9 2 a ) . T h u s , t h e e f f e c t s o f e x p o s u r e t o C O 2 a n d t e m-

pera ture a re in te rac t ive , bu t l i te ra ture showing p lan t

r e s p o n s e s t o e l e v a t e d a tmo s p h e r i c [ C O 2 ] a t d i f f e r e n t

t e mp e r a tu r e s i s l im i t ed . I t i s imp o r t a n t t o q u a n t i f y t h e

e f f e c t s o f [ C O 2 ] a n d t e mp e r a tu r e s o n p l a n t s b e c a u s e

th e s e v a r i a b l e s c a n h a v e a l a r g e imp a c t o n g r o w th ,

d e v e l o p m e n t a n d y i el d .

T h e o b j e c t i v e o f t h is s t u d y w a s t o e v a lu a t e t h e i n t er -

a c t i v e e ff e c t s o f t e mp e r a tu r e a n d C O 2 o n p h o to s y n th e -

s i s, t r a n s p i ra t i o n , w a t e r - u s e e f f i c i e n c y , an d d r y m a t t e r

a c c u m u la t i o n b y c o t t o n .

2 . M a t e r i a l s a n d m e t h o d s

2.1. Plant culture

I n E x p e r i m e n t I, u p l a n d c o tt o n ( c v . D P L 5 0 ) w a s

s o w n 8 J u ly 1 9 89 i n to s a n d - v e r m ic u l i t e ( 3 :1 v / v ) i n

p o ly v in y l - c h lo r i d e p o t s ( 0 . 1 5 m d i a me te r , 0 .6 7 m

dee p) a s desc r ibed b y Red dy e t a l . ( 1991 a ) . The p lan ts

w e r e g r o w n in t h e n a tu ra l e n v i r o n m e n t u n t il f i rs t b lo o m

a n d t h e n mo v e d i n to n a tu r a l l y l i t p l a n t g r o w th c h a m-

b e r s i n t h r e e r o w s w i th a p o p u l a t i o n o f n in e p l a n t s m - 2 .

T h e s e c h a m b e r s w e r e d e s c r i b ed i n d e t a il b y A c o c k e t

a l . (1 9 8 5 ) a n d R e d d y e t a l. ( 1 9 9 1 a ) . T h e p l a n ts w e r e

i r r ig a t e d t h r e e t ime s p e r d a y w i th h a l f - s t r e n g th H o a g -

l a n d ' s n u t r i e n t s o lu t i o n ( H e w i t t , 1 9 5 2 ) v i a a d r i p ir r i-

g a t i o n s y s t e m. T h e c h a mb e r s w e r e s e t a t 3 0 /1 8 C

( + 0 .1 C , d a y /n ig h t ) a n d ma in t a in e d a t 3 5 0 , 4 5 0 , 6 0 0 ,

7 5 0 , a n d 9 0 0 /x l C O 2 1 - ~ a i r ( + 1 0 /x l 1 - 1 ) d u r in g t h e

d a y l i g h t . P l a n t s w e r e g r o w n in t h e t e mp e r a tu r e - a n d

C O 2 - c o n t r o l l e d c o n d i t i o n s f o r 2 2 d a y s . T h e s e p l a n t s

a c h i e v e d c o m p le t e c a n o p y c lo s u r e , 9 8 s o l a r r a d i a t io n

in t e r c e p t e d a s me a s u r e d b y c o n t i n u o u s m o n i to r i n g w i th

a mo d e l L I 1 9 1 S B r a d i a t i o n s e n s o r ( L I - C O R , I n c . ,

L in c o ln , N E ) l o c a t e d a t t h e b o t t o m o f t h e c a n o p y , a f te r

o n ly 2 d a y s i n t h e g r o w th c h a m b e r . G r a d e d s h a d e c lo th s

w e r e a d ju s t e d a r o u n d t h e p l a n t s t o s imu la t e s h a d in g

e f f e c t s f o u n d i n a f ie l d cr o p . G a s - e x c h a n g e d a t a w e r e

s u mma r i z e d a n d p h o to s y n th e s i s c a l c u l a t e d d a i l y a s

d e s c r i b e d b e lo w . P h o to s y n th e s i s a t 1 6 0 0 / _ tmo l m - 2

s - 1 w a s a v e r a g e d o v e r 1 4 d a y s i n w h i c h p e a k P P F D

e x c e e d e d 1 6 0 0 ~ m o l

m 2 s 1 .


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V.R. Reddy et al. / Field Crops Research 41 (1995) 13-23

15

I n E x p e r i m e n t I I , D P L 5 0 p l a n ts w e r e g r o w n f r o m

s e e d i n t h e c o n t r o l l e d - e n v i r o n me n t c h a mb e r s . S e e d

w e r e g e r m i n a t e d i n m o i s t e n e d p a p e r t o w e l s a t 2 8 / 2 3 C

d a y /n ig h t t e m p e r a tu r e s f o r 4 8 h . T h e g e r m in a t e d s e e d,

w i th r a d i c a l s e me r g in g , w e r e s e l e c t e d f o r u n i f o r mi ty

a n d p l a n t e d o n 3 Ma r c h 1 9 8 9 i n to c h a mb e r s o i l b in s

f i l l e d w i th a mix tu r e o f s a n d a n d v e r mic u l i t e ( 3 :1

v

v ) . P l a n t s w e r e s p a c e d 1 0 c m a p a r t i n t h r e e 0 . 6 6 - m

row s ( 15 p lan ts m-2). T h e p l a n t s w e r e i r r i g a t e d w i th

a d r i p - i r r ig a t i o n s y s t e m w i th o n e e mi t t e r p e r p l a n t , t h r ee

t i m e s a d a y w i t h h a l f - s tr e n g t h H o a g l a n d s s o l u ti o n

( H e w i t t , 1 9 5 2 ) . A m o u n t o f w a t e r a n d t h u s n u tr i e n t s

s u p p l i e d d e p e n d e d o n t h e p r e v io u s d a y s t r a n s p i r a t io n .

T o a v o id p l a n t d a ma g e , i n s e c t s w e r e c o n t r o l l e d b y

s p r a y in g a p p r o p r i a t e i n s e c t ic i d e s .

T h e t e mp e r a tu r e - a n d C O 2 - c o n t r o l l e d c h a mb e r s

w e r e m a i n t a i n e d at 2 8 / 2 3 C ( + 0 . I C , d a y / n i g h t ) f o r

1 4 d a y s a f t e r e me r g e n c e ( D A E ) . A t t h a t t ime , th e c o t -

y l e d o n s o f t h e c o t t o n p l a n t s w e r e f u l l y e x p a n d e d a n d

th e p l a n ts w e r e 3 0 m m in h e ig h t. T e m p e r a tu r e a n d C O 2

t r e a tme n t s w e r e imp o s e d 1 5 D A E . T h e r e a f t e r , a i r t e m-

p e r a tu r e s i n t h e c h a mb e r s w e r e ma in t a in e d a t 2 0 /1 2 ,

2 5 / 1 7 , 3 0 / 2 2 , 3 5 / 2 7 C ( + 0 . 1 C ) u n t il t h e p l a n ts

w e r e h a r v e s te d , 7 0 D A E . D e w p o i n t t e m p e r a t u re s w e r e

n o t c o n t r o l l e d , b u t me a s u r e d a t 1 0 - s i n t e rv a l s w i th g o ld

mi r r o r h y g r o m e te r s i n s t a l l e d i n s id e t h e r e tu r n a i r l i n e .

T h e a v e r a g e d a y t i m e a n d n i g h t ti m e d e w p o i n t t e m p e r -

at ur es w er e 18.1 C +__0.38 and 15 .5C + 0 .39 dur ing the

f i r s t 1 4 d a y s ( p r i o r t o t e mp e r a tu r e t r e a tme n t ) . V a p o r

p r e s s u r e d e f i c i t s , c a l c u l a t e d b e tw e e n d e w p o in t a n d

c h a mb e r t e mp e r a tu r e s , v a r i e d l i t t l e d u r in g d a y t ime

h o u r s w h i l e i n c r e a s in g f r o m n e a r 1 .2 k P a a t 2 0 C to

n e a r 3 . 0 k P a a t 3 5 C . T h e r e w e r e n o d i f f e r e n c e s

b e tw e e n C O 2 l e v e l s ma in t a in e d a t t h e s a me a i r t e mp e r -

a tu r e s. D a y t im e t e mp e r a tu r e s w e r e i n i t ia t e d a t s u n r i se

a n d r e tu r n e d t o n ig h t t ime t e m p e r a tu r e 1 h a f t e r s u n s e t.

T h e C O 2 c o n c e n t r a t i o n s w e r e ma in t a in e d a t 3 5 0 a n d

7 0 0 / x l 1 - 1 a i r ( + 1 0 / x l 1 - 1 ) f o r e a c h t e mp e r a tu r e

u t i l i z i n g e ig h t c o n t r o l l e d - e n v i r o n me n t c a b in e t s .

G r a d e d s h a d e s s u r r o u n d e d t h e p l a n t s t o s imu la t e b o r d e r

p l a n t s . A l l t h e p l a n t s w e r e d i s s e c t e d a t h a r v e s t i n to

leaves , s tem, roo ts , and f ru i t ing s t ruc tures , d r ied , and

th e p a r ts w e ig h e d . W h e n t h e p l a n ts w e r e g r o w n a t n e a r

o p t i m u m t e m p e r a t u r e ( 3 0 / 2 2 C ) , t h e y p r o d u c e d a b o u t

15 bol l s pe r p lan t .

2 .2 . C a r b o n d i o x i d e a n d t e m p e r a t u r e c o n tr o l

C a r b o n d io x id e c o n c e n t r a t i o n , a i r t e mp e r a tu r e , a n d

i r r i g a t i o n i n t h e c h a mb e r s w e r e c o n t r o l l e d b y a c o m-

p u t e r a n d a d a t a a c q u i s i t io n s y s t e m th a t mo n i to r e d e n v i -

r o n me n ta l a n d g a s - e x c h a n g e v a r i a b l e s . C o n t in u o u s

c i r c u l a t i o n o f a i r ma in t a in e d u n i f o r m t e mp e r a tu r e s

t h r o u g h o u t t h e c h a m b e r s a n d l o w l e a f b o u n d a r y - l a y e r

r e s i s t a n c e . T h e c h a mb e r s w e r e s e a l e d , a n d t h e C O 2

c o n c e n t r a t i o n w a s m o n i to r e d a t 1 0 - s i n t e r v a ls a n d a v e r -

a g e d o v e r 9 0 0 - s p e r i o d s ( A c o c k e t a l. , 1 9 8 5 ) . C a r b o n

d io x id e w a s i n j e c t ed a u to m a t i c a l l y f r o m a g a s c y l i n d e r

in to t h e c h a m b e r s a s n e c e s s a r y t o ma in t a in t h e d e s i r e d

se t po in ts + 10/x l 1 - ~.

2 .3 . M e a s u r e m e n t o f p h o t o s y n t h e s i s a n d

t r a n s p i r a t i o n

S o la r r a d i a t i o n w a s me a s u r e d w i th a mo d e l 2 0 0 S B

p y r a n o m e t e r ( L I - C O R , I n c ., L in c o l n , N E ) a t a w e a t h e r

s t a t i o n a b o u t 5 0 m f r o m t h e s i te a n d s u m m a r i z e d w it h

a d a t a a c q u i s i t i o n s y s t e m a t 9 0 0 - s i n t e rv a l s .

D a t a f o r c a n o p y n e t C O 2 e x c h a n g e r a te s ( P n ) w e r e

s u m m a r i z e d o v e r t h e s a m e t i m e i n t e rv a l s. G r o s s p h o -

to s y n th e s i s ( P g ) w a s c a l c u l a t e d b y a d d in g d a r k r e s p i -

r a t i o n ( R d ) t o o b s e r v e d n e t p h o to s y n th e s i s (Pn)

P g = P n + R a

( 1 )

D a r k r e s p i r a t io n u s e d i n E q . 1 w a s t h e a v e r a g e r a te f o r

t h e f i rs t h o u r o f e a c h n ig h t w h i l e a i r t e mp e r a tu r e w a s

s t il l th a t ma in t a in e d d u r in g t h e d a y . C u r v e s o f P g v s. I

( p h o to s y n th e t i c p h o to n f l u x d e n s i t y , P P F D ) w e r e f i t te d

w i th a r e c t a n g u l a r h y p e r b o l a ( A c o c k e t a l. , 1 9 7 6 ) :

Pg = otlT C/ ( ogI + 7 C)

( 2 )

w h e r e a i s c a n o p y l i g h t - u t i li z a t i o n e f fi c i e n c y , ~ is ca n -

o p y c o n d u c t a n c e t o C O 2 t r a n s fe r , a n d C i s e x t e r n a l CO 2

c o n c e n t r a t i o n . T h e i n i t i al s l o p e o f t h e c u r v e i s a a n d

th e a s y m p to t i c v a lu e o f P g w h e n t h e l i g h t i s n o l o n g e r

l imi t ing i s ~C . Da i ly da ta for Pg and I were f i t ted wi th

E q . 2 u s in g t h e G a u s s - N e w to n n o n l i n e a r l e a s t - s q u a r e s

in t e r a c t iv e me th o d a s i n t e r p r e te d b y t h e S A S I n s t i tu t e

( 1 9 9 0 ) i n th e i r N L I N p r o c e d u r e . T h i s a l l o w e d i n t er -

p o l a t i o n o f s t a n d a r d P g r a t e s a t 1 6 0 0 / z mo l p h o to n s

m - 2 s - ~ .

C o n d e n s a t e w a t e r w a s c o l l e c t e d f r o m th e c o o l i n g

c o i l s a n d w e ig h e d a u to ma t i c a l l y e a c h 9 0 0 - s p e r i o d

( M c K i n i o n a n d H o d g e s , 1 9 8 5 ). T h i s c o n d e n s at e re p -


4/11

16

V.R. Reddy et al ./ Field Crops Research 41 1995) 13-23

r e se n t e d w h o le - c a n o p y t r a n sp i r a t io n a s a v a p o r b a r r i e r

w a s p l a c e d o v e r t h e so i l su r fa c e a n d s e a l e d a r o u n d th e

p l a n t s t e ms t o p r e v e n t e v a p o r a t i o n f r o m th e so i l. E x c e s s

i r r i g a ti o n e sc a p e d v i a a sm a l l o p e n in g i n t h e so i l b in .

2 4 Statistical procedures

S ta t i s ti c a l a n a ly se s t o t e s t d i f f e r e n c e s b e tw e e n t r e at -

m e n t s w e r e p e r f o r m e d u s in g d u m m y - v a r i a b l e r e g r e s -

s i on a n a l y s i s o f S A S G L M p r o c e d u r e s ( S A S I n s ti tu t e ,

1 9 9 0 ) . D i f f e re n c e s b e t w e e n t r e a t m e n t s o v e r t im e w e r e

d e t e r m in e d u s in g t e s t s f o r h e t e r o g e n e i ty o f s lo p e s a n d

- 5

I n

7

E 4

8

~

2

o

o l

o_

o

3 o

9

....~ 4 5

...',:

./ ~ 3 5

~

i i I i i

2 4 6 8

1000 1200 1400 1600

PPFD p mol m -2 e 1

F i g . 1 . C a n o p y g r o s s p h o t o s y n t h e s i s ( P g ) a s a f u n c t io n o f p h o t o s y n -

t h e t ic p h o t o n f l u x d e n s i ty ( P P F D ) 1 6 d a y s a f t e r b e g i n n i n g C O 2

t r e a t m e n t f o r f r u i t i n g c o t t o n p l a n t s g r o w n i n 3 0 / 1 8 C d a y / n i g h t

t e m p e r a t u r e s ( E x p e r i m e n t I ) . T h e r e g r e s s i o n l in e s w e r e e s t i m a t e d

b y a l e a s t - s q u a r e s f i t o f t h e 9 0 0 - s d a t a p o i n t s c o l l e c t e d t h r o u g h o u t

t h e d a y f o r e a c h t r e a t m e n t . F o r c l a r i ty , i n d i v i d u a l p o i n t s a r e p r e s e n t e d

o n l y f o r t h e 4 5 0 ~ 1 C O 2 1 -1 a i r t r e a t m e n t . V e r t i c al b a r s r e p r e s e n t

9 5 c o n f i d e n c e i n t e r v a ls f o r t h r e e C O 2 c o n c e n t r a t i o n s a t 1 2 0 0 / z m o l

r n - 2 s - 1

T a b l e 1

c o m p a r i s o n o f i n t er c e pt s f o r c a n o p y p h o t o s y n th e s i s ,

c a n o p y t r a n sp i r a t i o n a n d w a te r - u se e f f i c i e n c y . S t a n -

d a r d e r r o r o f e a c h me a n w a s c a l c u l a t e d a n d p r e se n t e d

in t h e f i g u r e s . E n v i r o n me n ta l c o n t r o l w a s ma in t a in e d

t h r o u g h o u t b o t h e x p e r i m e n t s a s d o c u m e n t e d b y 9 0 0 - s

m o n i t o r i n g l o g s . T h e c h a m b e r s w e r e d e s ig n e d t o a v o i d

h o t o r c o ld sp o t s , a n d w i th u n i f o r m w a te r a n d n u t r ie n t

a p p l i c a t i o n s , v a r i a n c e a mo n g p l a n t s w i th in e a c h c h a m-

b e r w a s sma l l . P r e v io u s r e p l i c a t e d e x p e r ime n t s d e m-

o n s t r a t e d t h a t t h e r e w a s mo r e v a r i a n c e w i th in t h a n

b e t w e e n c h a m b e r s .

3 R e s u l t s

3 1 Canopy photosynthesis an d respiration

I n E x p e r ime n t I , p h o to sy n th e s i s o f f r u i t i n g c o t t o n

p l a n t s i n c r e a se d

a s C O 2

a n d P P F D in c r e a se d ( F ig . 1 ) .

T h e r e w e r e d i f f e r e n c e s i n c a n o p y l i g h t - u t i li z a t io n e f f i -

c i e n c y ( i n i t ia l s l o p e s o f c u r v e s w h e n P P F D w a s l imi -

t i n g ) b u t t h e r e sp o n se s d id n o t i n c r e a se l i n e a r ly w i th

a d d i t i o n a l C O 2 . A l so , t h e d i f f e r e n c e s w e r e n o t c o n s i s -

t e n t f r o m d a y t o d a y ( T a b le 1 ) . T h e r e w e r e i n c r e a se s

in P g t h r o u g h o u t t h e b o l l - f i l l i n g p e r io d w i th t h e

in c r e a se s b e in g g r e a t e r w i th e l e v a t e d [ C O 2 ] ( d a t a n o t

s h o w n ) . T h e r e s p o n s e t o a d d i t i o n a l P P F D d e c r e a s e d

a s r a d i a ti o n i n c r e a se d p a r t i c u l ar l y f o r c a n o p ie s g r o w n

in l o w e r C O 2 c o n c e n t r at i o n s . A v e r a g e P g r a t e s a t 1600

/x mo l m - 2 s - ~ P P F D o b se r v e d d u r in g a 1 4 - d p e rio d

for p lan ts in Ex per im ent I a re il lus t ra ted in F ig . 2 . Th e

P g o f p l a n t c a n o p i e s a v e r a g e d 3 4 m o r e w h e n g r o w n

C a n o p y l i g h t u t i li z a t i o n e f f i c ie n c y ( a ) a n d c a n o p y c o n d u c t a n c e t o C O 2 t r a n s f e r ( ~ -) f o r c o tt o n c a n o p i e s g r o w n i n 3 5 0 a n d 7 0 0 / . t l C O 2 1 - ~ a i r

a t v a r i o u s t e m p e r a t u r e s ( E x p e r i m e n t I I ) . S t a n d a r d e r r o r s o f t h e m e a n a r e g i v e n

D a y s a f t er e m e r g e n c e T e m p . ( C ) a ( / x m o l C O 2 / x m o l - l p h o t o n s ) ~- ( ran ) S - - 1

3 5 0 / x l C O 2 1 i a i r 7 0 0 / x l C O 2 1 - l a i r

3 5 0 p ,1 CO 2 1 1 a i r 7 0 0 / ~ 1 CO z I 1 a i r

6 4

7 0

20 /1 2 0.0 14 __+0.00 2 0 .011 5- 0 ,001 1 .2 5- 0 .09 0 ,3 5- 0 .05

2 5 / 1 7 0 .0 5 2 __ 0 .0 0 4 0 .0 4 5 5 - 0 .0 0 3 7 .5 + 0 .3 9 4 .9 + 0 .3 6

3 0 / 2 2 0 .0 5 5 + 0 .0 0 4 0 .0 8 4 + 0 .0 0 5 9 .1 __ 0 .5 5 6 .7 + 0 .2 9

3 5 / 2 7 0 .0 5 7 + 0 .0 0 5 0 .0 6 8 5 - 0 .0 0 3 1 0 .3 + 0 .6 8 8 .1 + 0 .3 1

20 /1 2 0.0 18 +__0.0 03 0.0 27 _____.00 2 1.8 5- 0.1 9 0.5 0,2 9

25 /1 7 0 .066 __ 0 .00 3 0 .06 4 5- 0 .003 9 .0 __+0 .3 5 7 .0 + 0 ,4 6

3 0 / 2 2 0 .0 6 1 0 .0 0 3 0 ,0 7 7 5= 0 ,0 0 3 1 1 .8 0 .6 8 9 .6 0 ,4 2

35 /2 7 0,0 57 __+0,003 0 ,07 7 5- 0 .003 14.7 5- 0 .97 11.4 5- 0 ,61


5/11

V.R. Reddy et al. / Field Crops Research 41 1995) 13-2 3

1 7

i 5

m

?

E

o

J :

~ 3

=

o 2

Y - 1 . 2 4 4 6 + 0 . 0 0 7 2 4 X - 0 . 0 0 0 0 0 4 2 1 X 2 , r = - O . g 9

3 0 / 1 8

C

(~ 3 0 0 4 0 0 5 0 0 6 0 0 7 0 0 8 0 0 9 0 0

C O 2 C o n c e n t r a t i o n ( # 1 1 - 1 )

Fig. 2. Canopy gross photosynthesis of fruiting cotton canopies to

different atmosphe ric CO2 concentrations at a ph oton flux density of

1600/~mol m -2 s - 1 (Experiment I). Rates at 1600/zmol m - : s- 1

were estimated from a least-s quares fit of the 900-s data points col-

lected throughout each day for each treatment when photosynthetic

flux density exceeded 1600/.Lmol m -2 s-~, and those values aver-

aged for the 14 days _ standard error of the mean.

6

I m

?E 4-

2

~

-g

~3 2

0

- - - 350 ~1 1-1

C O 2 2 0 / 1 2 C

- - 700 #1 I I C O 2

2 5 / 1 7 %

5 0 0

1 0 0 0 1 5 0 0 2 0 0 0

I

3 5 / 2 7 C

5 0 0 1 0 0 0 1 5 0 0 2 0 0 0

PPFD ( /~mol m -~ a 1)

Fig. 3, Responses of canopy gross photosynthetic rate (Pg) to pho-

tosynthetic photon flux density (PPFD) 64 DAE for cotton grown

in various temperatures at 350 and 700/xl CO~ 1-1 air (Experim ent

It ). For simplicity, individual point s are provided only for the 350

/xl 1-i at 25/17 C. Vertical bars represen t 95 confidence interva ls

at 1600/zmol m -2 s J.

i n 9 0 0 / z l C O 2 1 - ~ a i r t h a n w h e n g r o w n i n 3 5 0 / z l 1 - 1.

C a n o p y p h o to sy n th e t i c c a p a c i t y o f f r u i t i n g p l a n t s

r e a c h e d m a x i m u m v a l u e s a t 7 0 0 / z l l - ~ C O 2 a n d f o l -

l o w e d b y a l e v e l i n g r e sp o n se f r o m 7 0 0 to 9 0 0 /x l l - ~.

I n E x p e r i m e n t I I , c a n o p y p h o t o s y n t h e s i s o f p l a n t s

g r o w n f r o m se e d , e x p r e s se d o n a g r o u n d - a r e a b a s i s ,

w a s g r e a t e r a t 7 0 0 /x l C O 2 l - ~ a i r th a n t h a t o f p l a n ts

g r o w n in 3 5 0 ~ l i ] a t a l l f o u r te mp e r a tu r e s ( F ig . 3 ) .

P h o to sy n th e s i s i n c r e a se d a s t e mp e r a tu r e i n c r e a se d t o

3 0 / 2 2 C i n b o t h C O 2 c o n c en t r at i o n s. C a n o p y p h o t o -

sy n th e s i s a t 1 6 0 0 P P F D /x mo l m - 2 s - ~ i n c r e a se d

8

6

4

A

~ m 2 1

?

E 0

o 6

- ; 4

~

2

E

0

o a

o

4

O

3 5

o - o 3 5 0 /4 1 1 ~ C O 2 2 5 / 1 7 C

7 0 0 / 41 1 I C O 2

i I I I I I I

3 0 / 2 2 C

e

I I I I I I I

3 5 / 2 7 C

4 0 4 5 5 0 5 5 6 0 6 5 7 0 7 5

ays f t e r E m e r g e n c e

Fig. 4. Effects of temperature and CO2 concentration on cotton can-

opy gross photosynthetic rate (Pg) at a photon flux density of 1600

/zmol m -2 s-1 (Experime nt II), The vertical bars represent 95

confidence intervals from the regression equation fit to each da y's

data at 40, 54 and 64 DAE. Regression parameters are presented

Table 2,

Table 2

Parameters for linear equations regressing canopy photosynthesis (y,

mg CO2 m 2 s- 1 as a function of days after emergence (x) where

y = bo + blx (Experiment It)

Temperature CO2 Regression

(da y/ni ght) ( ~11 - ' ) parameters

(C)

b~) b~

F

25/1 7 350 -2 .4 43 0.0854 0.98

700 - 2.591 0.0962 0.93

30/ 22 350 - 2,059 0.0878 0.97

700 - 1.390 0.1036 0.93

35/ 27 350 - 1.309 0.081 0.97

700 - 1.901 0.117 0.90

aThe intercepts are significantly different (P =0 .0 5) between CO2

levels within temperatures at 25/17 and 30/22C and between tem-

peratures within CO2 level.

~Fhe slopes differ significantly (P =0 .0 5) between CO2 levels at

35/27C.


6/11

18 V.R . Red d y e t a l. / F i e l d Cro p s Res ea rch 4 1 1 9 9 5 ) 1 3 -2 3

1 . 0

Io )

E

o

o

cL

o

0 . 8

0 . 6

0 . 4

0 350 ~41i 1 0= y - -1.31 772 + o.tl1344~tx - 0.001708 R . O.gtl

700 k~ i 1 co, y - -1,6e@89 + 0.13048(lex - 0.001773 R . 0.99

18 2 t 2 4 2 7 3 0 3 3 3 8

T e m p e r a t u r e ( C )

Fig. 5, Respiration rates of cotton canopies grown at various tem-

peratures and CO2 concentrations of 350 and 700/ zl 1- ~air Exper-

iment II). The data were averaged from 35 to 69 DAE and standard

errors of the means are sh own where they are larger than the symbols.

The data are expre ssed on a ground area basis.

c o n t i n u o u sl y f r o m 4 0 t o 7 0 D A E i n b o th C O 2 c o n c e n -

t r a ti o n s a t al l t e mp e r a t u r e s F i g . 4 , T a b l e 2 ) . Ph o t o -

s y n t h e t i c r a t e s o f p l a n ts i n 3 5 0 / x l 1 - ~ a t 7 0 D A E w e r e

mo r e t h a n d o u b l e t h e r a te s o f t h e s a me p l a n ts 4 0 D A E ;

a n d p l a n t s g r o w i n g i n 7 0 0 / z l 1 - 1 w e r e f i x i n g c a r b o n

t h r e e t i me s m o r e r a p i d l y a t 7 0 D A E t h a n a t 4 0 D A E .

Ph o t o s y n t h e t i c r a te s o f p la n t s g r o w i n g a t 7 0 0 / ~1 1 -

a n d i n 3 5 / 2 7 C i n c r e a s e d s i g n if i c a n tl y fa s t e r th a n f o r

p l a n ts g r o w i n g i n 3 5 0 / x l 1 - ~ a t t h e s a me h i g h t e mp e r -

a t u re s . T h i s d i f f e r e n c e w a s p r o b a b l y d u e t o t h e m o r e

r a p i d a d d i t io n o f n e w l e a v e s b y p l a n ts g r o w i n g i n h i g h

CO 2 a n d h i g h t e mp e r a t u r e . Ra p i d a d d i t i o n o f n e w

l e a v e s p r o v i d e s t h e c a n o p y w i t h a p o p u l a t i o n o f

y o u n g e r l e a v e s t h a t mo r e e f f e c t i v e l y r e s p o n d t o t h e

h i g h CO 2 Re d d y e t a l. , 1 9 9 4 ) . Ph o t o s y n t h e t i c r a te s o f

p l a n ts g r o w i n g i n 7 0 0 / ~1 CO z 1 -~ a i r a t 2 5 / 1 7 C a n d

3 0 / 2 2 C w e r e g r e a t e r t h a n p la n t s g r o w i n g i n 3 5 0 / x l

1 ~, bu t the c hanges in ra t es wi th ag e o f the p lan t s w ere

n o t d i f f e r e n t b e t w e e n CO 2 l e v e l s .

T h e c h a n g e s i n r e s p i r a t io n r e f l e c t e d c h a n g e s i n t e m-

p e r a t u r e a n d a c c u m u l a t e d d r y ma t t e r. Ca n o p y r e s p i r a -

t i o n o f p l a n t s g r o w n i n 7 0 0 / x l CO z 1 - ~ a i r in c r e a s e d a s

t e mp e r a t u r e in c r e a s e d F i g . 5 ) . Re s p i r a t i o n r a t e s o f

p lan t s in ambien t CO2 were g rea tes t a t 30C. The

i n c r e a s e i n r e s p i r a t io n w i t h e l e v a t e d CO 2 a n d i n c r e a s e d

p h o t o s y n t h e s i s p r o b a b l y w a s d u e m o s t l y t o th e g r e a t e r

a mo u n t o f b i o ma s s p r e s e n t l e a d i n g to mo r e ma i n te -

n a n c e ) a n d t o t h e f a s t e r g r o w t h r a te l e a d i n g to mo r e

r e s p i r a ti o n a s s o c i a t e d w i t h b i o s y n t h e s i s ) .

3.2. Canop y l ight ut i l izat ion ef f ic iency and can opy

conductance to carbon diox ide t ransfer

Ca n o p y l ig h t - u ti l iz a t i o n e f f i c i e n c y ~ ) w a s g r e a t e r

i n p l a n ts g r o w n in h i g h e r [ CO 2 ] T a b l e 1 ) . T h e c t

v a l u e s t e n d e d t o i n c r e a s e a s t e mp e r a t u r e i n c r e a s e d t o

30C da y) bu t we re incons i s t en t a t 35C. Large a

v a l u e s w e r e g e n e r a l l y a s s o c i a t e d w i t h t r e a tme n t s h a v -

i n g h i g h g r o w t h r a t e s . Ca n o p y c o n d u c t a n c e t o CO 2

t r a n s f e r ~ -) f o r c a n o p i e s i n 3 5 0 a n d 7 0 0 / z l CO 2 1 - 1

600

T

o)

4 0 0

E

C ) ~ 2 0 0

0

600

~ . 4 0 0

~ 2

6

i i i r i

o 3 , 5 0 / ~1 I - I 0 0 2 2 0 / 1 2 * C

7 0 0 / ~ 1 1 - 1 C O 2

8 1 0 1 2 1 4 . 1 6 1 8 2 0

T i m e o f

= i

, 5 0 / 2 2 0

6 B 1 0 1 2 1 4 1 6 1 8 2 0

D a y h , C S T )

2 4 0 0

2000

I

I s o o E

1 2 0 0 ~

E

8 0 0

400

Fig. 6. Diurnal trends in canopy transpiration rates and photosynthetic photon flux density 62 DAE for cotton canopies grown at various

temperatures in 350 and 700/.d CO21 - l air Experim ent 11). The data points are 900-s measured values. Regression parameters are presented

Table 3.


7/11

V.R. Reddy et al. / Field Crops Research 41 1995) 13-23 19

Table 3

Parameters for quadratic equations regressing canopy transpiration

(y, mg H20 m -z s -l ) as a function of hours of the day ( x) where

y = bo + b ix + b2x2a (Experim ent II )

Temperature CO2

(day/night) (/zl l-~)

(C)

Regression parametersa r 2

bo bl b2

20/ 12 350 - 163 32 - 1.13 0.98

700 -9 1 19 -0 .6 5 0.98

25 / 17 350 - 728 146 - 5.30 0.99

700 - 625 124 - 4.48 0.99

30/ 22 350 - 1437 285 - 10.53 0.99

700 - 128 254 -9 .3 6 0.98

35/2 7 350 - 90 8 363 - 13.14 0.99

700 - 1653 327 - 12.06 0.98

aRegression lines are significantly different (P = 0.05 ) between CO2

levels within the temperatures and between temperatures within the

CO2 level.

8

6

4 -

- I -

2

7

o

E 0

o

t . )

-6

6

E

4

.~

o

_

8

6

4

2 6 / 1 7 C

o o

l I

3 0 / 2 2 0 0 0 3 5 0 1 1 -1 C O

7 0 0 1 I - ~ C O 2

I

3 5 / 2 7 C

_- o ~ _ - - - - - . . , . . Z

~ voo

8 10 12 14 16 18

T i m e of Day ( h , C S T )

Fig. 7. Diurnal trends in water-use efficiency 62 DAE o f cotton

canopies grown at 25/17C, 30/ 22C, or 35/ 27C and in 350 or 700

p,1 CO2 1- l air (Experi ment II ). Leaf areas o f plants grown in 700

/zl 1-l CO2 were 51, 35 and 49 more than those of similar plants

grown in 350/zl 1- l at the respective temperatures. Regression par-

ameters are presented Table 4.

a i r 6 4 a n d 7 0 D A E i n v a r i o u s t e mp e r a t u r e s a r e p r e -

sen ted in Tab le 1 . P lan t s g rown in 350 / z l 1 - ] had

s ign i f i can t ly l a rger z va lues than p lan t s g rown in 700

/z l 1 -~ on a l l days and a t a l l g rowing t empera tu res .

C a n o p y c o n d u c t a n c e i n c re a s e d w i t h i n c r e a s e d g r o w i n g

tempera tu res in bo th CO2 leve l s .

3 .3 . Transp i ra t ion and water use e ff i c iency

T h e d i u r n a l t re n d s o f c a n o p y t r a n s p i r a ti o n r a t e s o f

p l a n ts g r o w n i n 3 5 0 a n d 7 0 0 / z l 1 - 1 a t f o u r t e mp e r a t u r e s

( E x p e r i me n t I I ) , a n d t h e d i u r n a l t r e n d i n p h o t o s y n -

t h e t ic p h o t o n f lu x d e n s i ty ( PP FD ) a r e p r e s e n t e d f o r a

f a i r ly c lo u d - f r e e d a y ( D A E 6 2 ) i n F i g . 6 a n d T a b l e 3.

T r a n s p i r a t i o n r a t e s c l o s e l y tr a c k e d PPF D a t b o t h CO 2

leve l s and in a l l t empera tu res . Transp i ra t ion increased

s ign i f i can t ly wi th increas ing t empera tu re , wh i l e CO2

e n r i c h m e n t r e d u c e d t r a n s p ir a t io n a s m a l le r , b u t s i g n if -

i can t , amount a t a l l t empera tu res .

T h e l a r g e r p h o t o s y n t h e t i c ra t e s a n d t h e s l ig h t l y l o w e r

t ransp i ra t ion ra t es o f p lan t s g row n in h igh CO2 resu l t ed

i n g r e a t e r w a t e r - u s e e f f i c i e n c y ( F i g . 7 a n d T a b l e 4 ) .

A v e r a g e w a t e r - u s e e f f i c i e n c y i n c r e a s e d a b o u t 4 1 a t

2 5 / 1 7 C , 5 7 a t 3 0 / 2 2 C , a n d 5 2 a t 3 5 / 2 7 C b y

100 increase in CO2 conce n t ra t ion .

3.4. Dry matter accumulation

D r y ma t t e r a c c u mu l a t i o n r e f l e c t e d tr e a t me n t d i f f e r -

e n c e s i n c a n o p y p h o t o s y n t h e s i s c a u s e d b y t e m p e r a t u r e

Table 4

Parameters for linear equations regressing water-use efficiency (y,

mmol CO2 m ol i H20) as a function of hours of the day (x) where

y = bo + blx (Experiment II)

Temperature CO2 Regression

(day/ni ght) (/zl 1- ') parameters

(C)

b~ b~

r~

25/1 7 350 5.386 -0. 002 73 0.77

700 7.239 - 0.00367 0.73

30/2 2 350 3.893 -0 .0 020 4 0.69

700 5.162 -0. 001 75 0.68

35/2 7 350 3.640 -0. 002 13 0.59

700 4.223 -0. 001 29 0.47

aThe intercepts are significantly different ( P = 0.05) betwe en CO2

levels within temperatures, and betwe en temperatures at the 350/z l

1- l level.

bThe slopes diffe r significantly (P = 0.05) between temperatu res at

700/xl CO21- t air.


8/11

2 0 V . R . R e d d y e t al . / F i e l d C r o p s R e s e a r c h 41 1 9 9 5 ) 1 3 - 2 3

1 5 0

1 2 5

1

7 5

5 0

2 5

0

T 7 O

o 6

m

o.

5 0

o~

4.0

~a

e

2

1

ca 0

7 O

6

5 0

4 0

3

2 O

1 0

0

I I I I

S t e m

Leof

L I I i

2 0 / 1 2 2 5 / 1 7 3 0 / 2 2 3 5 / 2 7

0 3 5 0 / J. L L - 1

C O 2

7 0 0 / ~L L - t

C O 2

1 6

1 2

8

1 6

t 2

8

R o o t

20 /12 25 /17 ~0 /22 35 /27

T e m p e r a t u r e *C )

F i g . 8 . D r y m a t t e r a c c u m u l a t i o n i n c o t to n p l a n t p a r t s a s a f f e c t e d b y t e m p e r a t u r e a n d C O 2 c o n c e n t r a t i o n s a t 7 0 D A E E x p e r i m e n t I I ) . S t a n d a r d

e r r o r s o f t h e m e a n s o f n i n e p l a n t s a r e s h o w n w h e r e t h e y a r e l a r g e r th a n t h e s y m b o l s .

a n d

C O

c o n c e n t r a t i o n s o f E x p e r im e n t I I (F ig . 8 ) .

M a x i m u m d r y m a t t e r a c cu m u l a t i o n o c c u r r e d i n p la n t s

g r o w n a t 3 0 / 2 2 C a t b o t h [ C O 2 ] , e v e n t h o u g h g r o s s

p h o to s y n th e s i s r a t e s w e r e s l i g h t l y g r e a t e r o n mo s t d a y s

f o r p l a n t s g r o w n a t 3 5 /2 7 a C . R e s p i r a t i o n r a t e s w e r e

a l s o g re a t e r i n p l an t s g r o w n a t 3 5 / 2 7 C c o m p a r e d t o

3 0 /2 2 C , r e s u l t i n g i n mo r e d r y ma t t e r a c c u mu la t i o n a t

3 0 / 2 2 C . D r y m a t t e r a c c u m u l a t i o n w a s g r e a t e r i n

p l a n t s g r o w n in a l l t e mp e r a tu r e s a t 7 0 0 /x l C O 2 l - 1 a i r

c o m p a r e d t o 3 5 0 p~l l - 1

4 D i s c u s s i o n

4 1 C anopy pho t os yn t hes i s and r es p ir a t ion

P h o to s y n th e s i s i n c r e a s e d r a p id ly w i th i n c r e a s e s i n

P P F D a n d s m a l l d if f e re n c e s d u e t o a t m o s p h e r i c C O 2

w e r e d e t e c te d v e r y q u i c k ly . I d s o a n d K i m b a l l ( 1 9 9 3 )

f o u n d t h a t e u c a ly p tu s a n d A u s t r a l i a n b o t t l e t r e e s

i n c r ea s e d p h o t o s y n t h e t i c r a te s c o n s i d e r a b l y m o r e w h e n

e x p o s e d t o h i g h C O 2 e n v i r o n m e n t s f o r a 4 - y p e r i o d

t h a n w h e n s i m i l a r t r ee s w e r e g r o w n i n a m b i e n t C O 2

e n v i r o n m e n t s , o r e x p o s e d t o h i g h c o n c e n t r a t i o n s o f

C O 2 f o r o n ly s h o r t p e r i o d s .

P l a n t s p l a c e d i n v a r y in g

C O

e n v i r o n m e n t s a t f l o w -

e r in g a p p e a r e d t o s a tu r a t e i n r e s p o n s e t o C O b e t w e e n

7 0 0 a n d 9 0 0 / x l C O 2 1 - 1 a i r ( F i g . 2 ) . T h i s r e sp o n s e is

i n c o n t r a s t t o t h e l i n e a r i n c r e a s e s i n P n f o u n d i n e u c a -

l y p t u s b e t w e e n 4 0 0 a n d 1 0 0 0 /x l 1 - 1 ( i d s o a n d K i m b a l l ,

1 9 9 3 ) . I t w a s s imi l a r , h o w e v e r , t o r ic e c a n o p i e s g r o w n

a t a r a n g e o f [ C O 2 ] ( B a k e r e t a l ., 1 9 9 0 ) . T h e l o w

[ C O 2 ] a t w h ic h t h e s e c o t t o n p l a n t s a p p e a r e d t o s a tu r a te

ma y h a v e b e e n d u e t o t h e l imi t a t i o n s i n s i n k a c t i v i t y .

T h e p l a n t s h a d j u s t b e g u n f l o w e r in g w h e n p l a c e d i n th e

c o n t r o ll e d e n v i r o n m e n t s a n d t h e y h a d o n l y a f e w y o u n g

b o l l s a t th e t ime o f t h e s e me a s u r e me n t s .

P h o to s y n th e s i s a t 2 0 /1 2 C w a s l e s s t h a n 1 m g C O 2

m - 2 s - 1 a t b o th C O 2 c o n c e n t r a t i o n s . T e m p e r a tu r e a t

2 0 / 1 2 C w a s m u c h m o r e l i m i t i n g t o p h o t o s y n t h e s i s

t h a n C O 2 a t t h e s e c o n c e n t r a t i o n s .

C a n o p y p h o to s y n th e s i s a t 1 6 0 0 / z mo l

m 2 s 1

P P F D w a s a b o u t 5 0 m o r e f o r y o u n g c o tt o n p l a n ts

g r o w n f o r 7 0 d in t h e h ig h C O 2 e n v i r o n m e n t ( F ig s . 3 ,

4 ) t h a n i n f r u it i n g c o t t o n t r a n s f e r r e d i n to h ig h C O z a t

f i r s t f l o w e r ( F ig . 2 ) . T h i s i s n o t s u r p r i s i n g a s p l a n t s

g r o w n f r o m s e e d l i n g s t o 7 0 d h a d t h e o p p o r tu n i t y t o

d e v e lo p a d d i t i o n a l s in k s c o m p a r e d t o p l a n t s g r o w n o u t -

s i d e a n d mo v e d i n to t h e c h a m b e r s a t f lo w e r in g .

T h e l e a f a re a i n d e x o f p l a n ts g r o w n i n E x p e r i m e n t

I I m o r e th a n d o u b l e d b e t w e e n 4 0 a n d 7 0 D A E ( R e d d y


9/11

V.R. Reddy et al. / Field Crops Research 41 1995) 13 -23

21

e t a l . , 1 9 9 4 ) . T h e Pg r a t e s w e r e t h u s e n h a n c e d b y

g r e a t e r l i g h t c a p tu r e a s w e l l a s g r e a t e r p h o t o s y n t h e t i c

c a p a c i t y a n d ra p i d g r o w t h ( F i g . 4 ) . D a y - t o - d a y v a r ia -

t i o n o b s e r v e d a t a l l te mp e r a t u r e s d i d n o t a p p e a r t o b e

t r e a t me n t - r e l a t e d . S i mi l a r d a y - t o - d a y v a r i a t i o n i n

c a n o p y p h o t o s y n t h e s i s w a s r e p o r t e d f o r c o t t o n ( Re d d y

e t al ., 1 9 9 1 a ) , f o r s o y b e a n ( D r e g e r e t a l. , 1 9 6 9 ; A c o c k

e t a l. , 1 9 8 5 ) , a n d f o r r i c e ( B a k e r e t a l ., 1 9 9 0 ) , b u t t h e

c a u s e o f th e v a r i a t i o n i s u n k n o w n .

Re s p i r a t i o n r a t e s a r e s t r o n g l y i n f l u e n c e d b y c a r b o -

h y d r a t e s u p p l y ( Ba k e r e t a l . , 1 9 7 2 ; Co g g e s h a l l a n d

H o d g e s , 1 9 8 0 ; M u l l e n a n d K o l l e r , 1 9 8 8; Re d d y e t a l. ,

1 9 9 1 a ) . Sp e c i f i c r e s p i r a t io n r a t e s o f p l a n t s g r o w n i n

h i g h CO 2 w e r e r e p o r t e d t o d e c r e a s e ( W u l l s c h l e g e r e t

a l. , 1992; ldso and Kim bal l , 19 93) . In th i s exp er im en t

b i o ma s s w a s me a s u r e d o n l y a t t h e e n d . I f o n e ma k e s

a n a s s u mp t i o n t h a t t h e r a ti o s o f b i o ma s s f o u n d i n t h e

CO 2 t r e a t me n t s a t t h e e n d o f t h e s t u d y r e p r e s e n t e d t h e

r a t i o s w h e n r e s p i r a t i o n me a s u r e me n t s w e r e t a k e n

t h r o u g h o u t t h e e x p e r i me n t , t h e n t h e p l a n t s g r o w n i n

7 0 0 / x l CO 2 1- i a i r w e r e r e sp i r i n g 1 6 l e ss p e r u n i t

a b o v e g r o u n d b i o ma s s t h a n t h o s e i n 3 5 0 / z l 1 -~ CO 2 .

A m t h o r ( 1 9 9 1 ) p r o p o s e d s e v e ra l a l t e rn a t i v e me c h a -

n i s ms t h a t m i g h t c a u s e a l t e r e d le v e l s o f r e s p i r a t io n a t

e l e v a t e d [ CO 2 ] . A mo r e l i k e l y si t ua t i o n in t h is e x p e r -

i me n t m a y b e t h a t p l a n ts g r o w n i n h i g h CO 2 f o r l o n g e r

p e r i o d s a c c u m u l a t e d mo r e b i o ma s s . M o s t o f t h a t ti s s ue

i s p robab ly s t ruc tu ra l par t s o r s to rage m ater i a l tha t has

o n l y a s ma l l r e s p i r a t o r y re q u i r e me n t .

4 . 2. T r a n s p i r a t i o n a n d w a t e r - u s e e ff i c i e n c y

T r a n s p i r a t i o n r a te s o f p l an t s g r o w n i n h i g h [ CO 2 ]

we re s ign i f i can t ly low er in a ll t empe ra tu res than p lan t s

g r o w n i n a m b i e n t CO 2 . T o t a l d a il y t r a n s p ir a t i o n w a s

1 8, 6 , a n d 5 l e ss in th e 7 0 0 / x l CO 2 1 - ~ a i r c o m p a r e d

a t 3 5 0 / z l 1 - 1 a t 2 5 / 1 7 C , 3 0 / 2 2 C , a n d 3 5 / 2 7 C ,

r e s p e c t i v e l y ( F i g . 6 ) . T h e s e d e c r e a s e s in c a n o p y t r a n -

s p i r at i o n o c c u r r e d in s pi t e o f 1 0 t o 1 5 mo r e l e a f a r e a

o f p l a n t c a n o p i e s g r o w n i n h i g h - CO 2 ( Re d d y e t a l . ,

1 9 9 4 ) . T h e e x a c t a m o u n t d e p e n d e d o n t e m p e r a t u re .

T h i s i n d i c a t e s g r e a t e r c a n o p y r e s i s t a n c e to w a t e r v a p o r

f l u x i n h i g h - CO 2 g r o w n c a n o p i e s . Ca n o p y w a t e r - u s e

e f f i c i e n c y d e c l i n e d w i t h i n c r e a s e d t e m p e r a t u r e d u e t o

i n c r e a s e d w a t e r lo s s . D o u b l i n g [ CO 2 ] e n h a n c e d w a t e r -

u s e e f f i c i e n c y ma i n l y d u e t o i n c r e a s e d p h o t o s y n t h e s i s .

S i mi l a r r e d u c t i o n s i n c a n o p y t r a n s p i r a t i o n w e r e

r e p o r t e d f o r ri c e ( B a k e r e t a l. , 1 9 9 0 ) a n d s o y b e a n

(Jon es e t a l ., 1985) wi th increas ing [CO2], . Us ing s im-

u l a t i o n mo d e l s , u n d e r a c l i ma t e - c h a n g e s c e n a r i o o f

i n c r e a s e d te mp e r a t u r e a n d d o u b l e d [ CO 2 ] , Cu r r y e t al .

( 1 9 9 0 ) p r e d i c t e d i n c r e a s e d w a t e r - u s e r a t h e r t h a n

d e c r e a s e d w a t e r r e q u i r e me n t s ( r e c i p r o c a l o f w a t e r - u s e

e f f i c i e n c y ) a s o b s e r v e d i n o u r s t u d ie s a n d o t h e r s ( J o n e s

e t a l ., 1985 ; Bake r e t a l ., 1990 ) .

4 .3 . D r y m a t t e r a c c u m u l a t i o n

T o t a l d r y ma t t e r i n c r e a s e d b y 6 a t 2 0 / 1 2 C , 3 0

a t 2 5 / 1 7 C , 4 5 a t 3 0 / 2 2 C , a n d 5 3 a t 3 5 / 2 7 C

p l a n t s g r o w n w i t h h i g h CO 2 c o mp a r e d p l a n t s g r o w n

w i t h a mb i e n t CO 2 ( F i g . 8 ) . D r y ma t t e r a c c u mu l a t i o n

increase d in a l l p l an t par t s exce p t f ru i t ing s t ruc tu res as

t e mp e r a t u r e i n c r e a s e d a t b o t h [ CO 2 ] l e v e l s . T h e

r e s p o n s e t o [ CO 2 ] w a s g r e a t e r w i th f a v o r a b l e g r o w i n g

t e mp e r a t u r e s . P l a n t s g r o w n i n h i g h [ CO 2 ] i n c r e a s e d

s t e m w e i g h t c o mp a r e d t o a mb i e n t CO 2 e n v i r o n me n t s

b y 1 9, 3 2 , 6 1 , a n d 8 1 a t 2 0 / 1 2 , 2 5 / 1 7 , 3 0 / 2 2 a n d

3 5 / 2 7 C , r e s p e c t i v e l y . A s i mi l a r r e s p o n s e t o i n c r e a s e d

[ CO 2 ] w a s o b s e r v e d i n le a f w e i g h t. T h e i n c r e a s e s i n

r o o t d r y ma t t e r w i t h h i g h a t mo s p h e r i c CO g w e r e 2 0 ,

1 6, 2 5 a n d 7 4 a t 2 0 / 1 2 , 2 5 / 1 7 , 3 0 / 2 2 a n d 3 5 /2 7 C ,

r e s p e c t i v e l y . T h e r e l a t i v e l y l a r g e i n c r e a s e i n r o o t

w e i g h t ( 7 4 ) a t 3 5 / 2 7 C w a s p r o b a b l y c a u s e d i n p a r t

b y m o r e r e a d i l y a v a i la b l e c a r b o h y d r a t e s d u e t o h i g h -

t e mp e r a t u r e - i n d u c e d f r u i t a b o rt i o n . I t w a s r e p o r t e d t h a t

h i g h t e m p e r a t u r e i n h i bi t s p r o d u c t i o n o f p o l l e n i n c o t t o n

( M e y e r , 1 9 6 9 ) a n d e n h a n c e s s q u a r e a n d f r u it a b o r t i o n

( Re d d y e t a l. , 1 9 9 2 b ) . Ca n o p y t e mp e r a t u r e w a s n o t

me a s u r e d i n t h e s e e x p e r i me n t s , b u t o t h e r s t u d ie s h a v e

s h o w n o n l y s ma l l m i d d a y d i f f e r e n c e s b e t w e e n a i r a n d

c a n o p y t e mp e r a t u r e s i n t h e s e c h a mb e r s . D i f f e r e n c e s in

r o o t g r o w t h d u e t o [ CO 2 ] d i d n o t r e s u l t i n a n y s h i f t i n

r o o t / s h o o t r a t i o o f p l a n ts i n a n y o f th e t e m p e r a t u r e

t rea tmen t s .

In ear l i e r f i e ld s tud ies where co t ton p lan t s were

e x p o s e d t o v a r i o u s t e mp e r a t u r e s f o r s h o r t p e r i o d s , i t

w a s c o n c l u d e d t h a t p h o t o s y n t h e s i s r a t e s w e r e n o t

r e s p o n s i v e t o t e mp e r a t u r e - ( Ba k e r , 1 9 6 5; B a k e r e t a l .,

1 9 7 2 ) . B y c o n t r a s t , in t h i s s t u d y , th e p l a n ts w e r e g r o w n

a t s e v e r a l w e l l - c o n t r o l l e d t e mp e r a t u r e s t h r o u g h o u t

mo s t o f t h e g r o w t h c y c l e , re s u l t in g i n l a r g e d i f f e r e n c e s

i n g r o w t h r a t e s a n d d e ma n d f o r c a r b o n . H i g h e r p h o t o -

s y n t h e t ic r a t e s a l so o c c u r r e d i n p l a n ts g r o w n a t t h e t w o

h i g h e r t e mp e r a t u r e s t h a n o c c u r r e d a t t h e t w o l o w e r


10/11

22

V .R . R e d d y e t a l . / F i e l d C r o p s R e s e a r c h 4 1 1 9 9 5 ) 1 3 - 2 3

t e mp e r a tu r e s . I t i s n o t f e a s ib l e t o s e p a r a t e c a u se a n d

e f f e c t f r o m th e se d a t a .

5 Co nc lus io ns

g r a m A g r e e m e n t N u m b e r 9 1 - 3 7 1 0 0- 6 6 2 6 . T h e

a u th o r s a p p r e c i a t e t h e c a p a b l e h e lp o f G a r y B u r r e l l

K i m b e r G o u r l e y W e n d e l l L a d n e r R a y m o n d S m i t h e y

a n d S a m T u r n e r f o r t e c h n i c a l a s s is t a n c e .

T h i s s t u d y e v a lu a t e d c o t t o n p l a n t s e x p o se d t o d i f -

f e r e n t a tmo sp h e r i c [ C O 2 ] a n d t e mp e r a tu r e s . T h e

g r e a t e s t e f f e c t o f h ig h C O z a tmo sp h e r e s w a s a t t e m-

p e r a tu r e s n e a r o p t im u m f o r g r o w th . L a r g e i n c r e a se s i n

p h o to sy n th e s i s a n d sma l l d e c r e a se s i n t ra n sp i r a t io n d u e

to d o u b l in g t h e a mb ie n t [ C O 2 ] r e su l t e d i n l a r g e

in c r e a se s i n w a te r - u se e f f i ci e n c y . L e a f a r e a s o f p l a n t s

g r o w n in h ig h C O 2 in c r e a se mo r e r a p id ly t h a n l e a f a r e a s

o f p l a n t s g r o w n in a m b ie n t C O 2 a n d t h e tw o e f f e c t s o f

e l e v a t e d C O 2 a r e so me w h a t c o mp e n sa t i n g u n t i l t h e

g r o u n d i s sh a d e d w i th l e a v e s . H o w e v e r a f t e r a fu l l

c a n o p y i s d e v e l o p e d o n e w o u l d e x p e c t t h e e f f e c t o f

d e c r e a se d t r a n sp i r a t i o n d u e t o i n c r e a se d s to m a ta l r e s is -

t a n c e o f p l a n t s g r o w n in h ig h C O 2 to d e p l e t e so i l mo i s -

t u r e mo r e s l o w ly . T h e p r o c e s se s s e n s i t i v e t o l e a f o r

so i l - w a te r s t a tu s w i l l b e l e s s e f f e c t e d b y e l e v a t e d C O 2 .

P la n t s g r o w n in 7 0 0 / z l C O 2 1 - J a i r h a d l a r g e i n c re a se s

in p lan t we ight .

P l a n ts g r o w n a t 3 5 / 2 7 C w e r e a b o v e o p t i m u m t e m -

p e r a tu r e f o r f r u i t r e t e n t i o n . D o u b l in g C O 2 d id n o t

in c r e a se ma ss i n f r u i t i n g s t r u c tu r e s c o mp a r e d t o

in c r e a se s i n v e g e t a t i v e s t r u c tu r e s a t t h e se h ig h e r t e m -

p e r a tu r e s . T e mp e r a tu r e s o f 3 5 /2 7 C a n d h ig h e r a r e

c o m m o n d u r i n g t h e f l o w e ri n g p e r io d s i n m a n y c o t t o n

g r o w in g a r e a s e v e n i n p r e se n t - d a y C O 2 e n v i r o n me n t s .

T h e a n t i c ip a t e d 3 t o 6 C r i s e i n a v e r a g e su mme r t e m-

p e r a tu r e s i n t h e U . S . c o t t o n b e l t w i l l b e v e r y d e t r ime n ta l

f o r co t t o n f r u i t p r o d u c t io n a s C O 2 e n r i c h me n t d id n o t

a me l io r a t e f r u i t r e t e n t i o n a t h ig h t e mp e r a tu r e s . O u r

r e su l t s d e mo n s t r a t e p r o sp e c t s f o r imp r o v e d p l a n t

g r o w th a n d y i e ld a t e l e v a t e d C O 2 b u t t h e r e sp o n se s a r e

h ig h ly t e mp e r a tu r e d e p e n d e n t . H e a t t o l e r a n t c u l t i v a r s

a r e n e e d e d w i l l b e mo r e p r o d u c t iv e a n d h a v e f e w e r

d e l a y s d u e t o a b sc i s e d fr u it i n t h e p r e se n t - d a y C O 2

w o r ld . T h e y w i l l su r ely b e mo r e e s se n t i a l i n a w a r m e r

g lo b a l c l ima te .

A c k n o w l e d g e m e n t s

T h i s r e se a r c h w a s f u n d e d i n p a r t b y t h e U S D A -

N a t io n a l R e se a r c h I n i t i a t i v e C o mp e t i t i v e G r a n t s P r o -

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a n d m a i n t e n a n c e r e s p i r a t i o n i n l e a v e s o f

Liriodendron tulipifera

L . e x p o s e d t o l o n g - t e r m c a r b o n d i o x i d e e n r i c h m e n t i n th e f i e l d .

N e w P h y t o l . , 1 2 1 : 5 1 5 - 5 2 3 .

carbon dioxide enrichment and temperature effects on cotton

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