Growth-Regulating Action of Brassinolide in Rice Plants - American

Chapter 27 Growth-Regulating Action of Brassinolide in Rice Plants 1

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S. Fujii , K. Hirai , and H. Saka

Downloaded by UNIV OF ARIZONA on January 8, 2013 | http://pubs.acs.org Publication Date: November 4, 1991 | doi: 10.1021/bk-1991-0474.ch027

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Shiraoka Research Station of Biological Science, Nissan Chemical Industries, Ltd., Shiraoka, Minamisaitama, Saitama 349-02, Japan Hokkaido National Agricultural Experimental Station, Sapporo, Hokkaido 062, Japan

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Brassinolide increased the grain weight and the percentage of ripened grains i n rice plants. Brassinolide treatment promoted assimilation of C in leaf blades and successive translocation of the radioactive assimilate into panicles. Accumulation of starch in panicles was enhanced by brassi nolide treatment. The effect of brassinolide on the ripen ing of rice plants may be attributed to the enhancement of the synthesis and translocation of photosynthetic products. It was found that brassinolide treatment altered the levels of endogenous indole acetic acid and abscisic acid in panicles. 14

In wheat, the ear weights of both t i l l e r s and the main stem were i n creased, in comparison with untreated controls by brassinolide (BR) sprays (1). In corn, BR treatment had significant influence on the length of the unfertile tip portion of the ear and on the number of vacant kernels. The yield increased compared with untreated controls (2). L i t t l e i s known of the effect of BR on the ripening of rice plants, and the mode of action of BR on the ripening of rice has not been studied. To increase crop yield, i t i s necessary to improve the photosynthetic efficiency and promote the translocation of photosyn thetic products in the panicles. Therefore, we assessed the ripening of rice, the translocation of photosynthetic products, and plant hormone levels in panicles. Increase of Grain Weight and Percentage of Ripened Grains R i c e (Oryza sativa L . c v . Nipponbare) seeds were d i r e c t l y sown i n p o t s and grown i n a greenhouse before h e a d i n g . BR was sprayed w i t h 30 ml per pot a t c o n c e n t r a t i o n s o f 10~^ and 10~^ppm 10 days before

0097-6156/91/0474-0306S06.00/0 © 1991 American Chemical Society In Brassinosteroids; Cutler, H., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1991.

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Growth-Regulating Action in Rice Plants


heading and heading t i m e , r e s p e c t i v e l y . A f t e r f l o w e r i n g , r i c e p l a n t s were grown i n a greenhouse or a p h y t o t r o n ( 2 0 ° C / 1 3 ° C ) . Under g r e e n house c o n d i t i o n s ( T a b l e I A ) , BR i n c r e a s e d the g r a i n weight and the percentage o f r i p e n e d g r a i n s o f r i c e p l a n t s a t 3 weeks a f t e r heading and the percentage o f ripened grains a t 6 weeks. M o r e o v e r , under p h y t o t r o n c o n d i t i o n s ( T a b l e I B ) , BR g r e a t l y i n c r e a s e d both the g r a i n weight and the percentage o f r i p e n e d g r a i n s a t 3 and 6 weeks a f t e r h e a d i n g . BR e x c e r t s i t s e f f e c t i v e n e s s most e s p e c i a l l y under e n v i r o n mental c o n d i t i o n s o f s t r e s s . And BR i n c r e a s e d the weight o f g r a i n s l o c a t e d i n a l l r a c h i s - b r a n c h e s , but i n p a r t i c u l a r , the w e i g h t o f those g r a i n s l o c a t e d i n the l o w e r b r a n c h e s . Table I . E f f e c t of Brassinolide on Weight of Grain i n Rice Plants (cv.Nipponbare) under (A) Greenhouse and (B) Phytotron(20°C/13°C) Conditions

IA1 BR

3 Weeks a f t e r Heading

(ppm) Weight o f 1000 grains(g)

0 1(T IO"

3

2

6 Weeks a f t e r Heading

Percentage o f

Weight of

Percentage of

ripened grains(%)

1000 grains(g)

ripened grains(%)

18.0

50.3

23.3

75.3

19.2 19.5

61.2

23.6 23.2

82.6 81.0

63.8

(B) BR (ppm)

grains(g) 11.7

grains(%) 15.4

3

12.7

2

12.8

25.3 24.5

0 IO" IO"

3 Weeks a f t e r Heading Weight of Percentage of 1000 ripened

Translocation

6 Weeks a f t e r Heading Weight of Percentage of ripened 1000 grains(g) grains(%) 62.2 21.6 22.7 22.9

75.8 75.3

of

14c i n Riceand Plants. R i c e p l a n t s were grownincorporated i n a greenhouse t r e a t e d w i t h BR as d e s c r i b e d above. A t 3 days a f t e r h e a d i n g , r i c e p l a n t s were p l a c e d i n an a r t i f i c i a l l y c o n t r o l l e d growth chamber. From s m a l l v e s s e l s , which were p l a c e d i n t h e growth chamber, was r e l e a s e d by a c i d i f y i n g the N a H C 0 ( 1 7 . 5 MBq) w i t h H C 1 0 . R i c e p l a n t s were fed w i t h C0 f o r 1 h o u r . A l l o p e r a t i o n s of the a s s i m i l a t i o n procedure were p e r formed under l i g h t ( l i g h t i n t e n s i t y 550-660 m i c r o mols m ^ s ) a t 2 5 ° C . A f t e r f e e d i n g , r i c e p l a n t s were grown i n the same growth chamber. The p h o t o p e r i o d was 12h and temperature was m a i n t a i n e d a t 2 5 ° C . Amounts o f the l ^ C i n each p l a n t p a r t were determined a t r e g u l a r i n t e r v a l s . In 1 4

1 4

3

3

2

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In Brassinosteroids; Cutler, H., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1991.

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BRASSINOSTEROIDS: CHEMISTRY, BIOACTIVITY, AND APPLICATIONS

u n t r e a t e d c o n t r o l s , 63% o f the i n c o r p o r a t e d i n t o each r i c e p l a n t was p r e s e n t i n the l e a f b l a d e s 1 hour a f t e r f e e d i n g . S u b s e q u e n t l y , the 14 i n the l e a f b l a d e s r a p i d l y decreased and t r a n s l o c a t e d i n t o the culms and the g r a i n s . Most o f the 14C accumulated i n t o the culms from 1 t o 7 days a f t e r f e e d i n g . I n r i c e p l a n t s t r e a t e d w i t h BR, amounts o f 1 4 i n l e a f b l a d e s were p r e s e n t a t h i g h e r l e v e l s (126%) r e l a t i v e t o untreated c o n t r o l s at 1 hour, suggesting that a high photosynthetic r a t e was induced by BR i n the l e a f b l a d e . The 14c r a p i d l y decreased i n l e a f b l a d e s i n a s i m i l a r manner t o u n t r e a t e d c o n t r o l s . From 3 days a f t e r a s s i m i l a t i o n , amounts o f 14c i n g r a i n s g r e a t l y i n c r e a s e d . The increases of C i n t h e g r a i n a t 3, 7, and 21 days were 1 1 9 . 5 , 2 2 0 . 8 , and 443.3 Bq compared w i t h u n t r e a t e d c o n t r o l s ( 8 8 . 0 , 1 4 0 . 2 , 389.3 Bq) r e s p e c t i v e l y . The a c c u m u l a t i o n o f i n culms was suppressed(65%). These r e s u l t s show t h a t the t r a n s l o c a t i o n o f p h o t o s y n t h e t i c p r o d u c t s i n p a n i c l e s i s p r o b a b l y promoted by t r e a t m e n t w i t h BR. D i s t r i b u t i o n of Starch and Sucrose. L i t t l e s t a r c h was made i n the l e a f b l a d e s d u r i n g the r i p e n i n g o f r i c e . Most of the s t a r c h accumulated i n the p a n i c l e s . However, r i c e p l a n t s s t o r e d s t a r c h i n the l e a f sheaths and the culms t o some e x t e n t . Starch content i n the l e a f sheaths ( F i g u r e 1) and the culms under greenhouse c o n d i t i o n s was a p p r e c i a b l y l e s s than t h a t under p h y t o t r o n conditions. I n t h e c a s e o f t r e a t m e n t w i t h BR, s t a r c h c o n t e n t i n the l e a f s h e a t h s ( F i g u r e 1) and the culms was suppressed under both c o n d i t i o n s w h i l e t o t a l s t a r c h c o n t e n t s i n the p a n i c l e s i n c r e a s e d ( F i g u r e 2 ) . So i t i s proposed t h a t the decrease o f the s t a r c h c o n t e n t i n the l e a f sheaths and t h e culms may be c o r r e l a t e d t o the r i p e n i n g o f the r i c e p a n i c l e s , t h a t i s , the i n c r e a s e o f g r a i n w e i g h t and t h e percentage o f r i p e n e d g r a i n s . I n a d d i t i o n , s u c r o s e c o n t e n t i n p a n i c l e s i n c r e a s e d by BR t r e a t m e n t under both c o n d i t i o n s . I t may be c o n c l u d e d t h a t BR e n hances the a c c u m u l a t i o n o f s t a r c h and s u c r o s e i n the p a n i c l e s . The r e c o n s t i t u t i o n of the s t a r c h i s p r o b a b l y promoted i n t h e p a n i c l e s , not i n l e a f s h e a t h s o r c u l m s . Plant Hormone Levels i n the Panicles. c


C

1 4

_3

U n t r e a t e d r i c e p l a n t s and those t r e a t e d w i t h BR ( 1 0 p p m ) were grown in a greenhouse or a p h y t o t r o n ( 2 2 ° C / 1 7 ° C ) after flowering. The weight o f g r a i n s s i g n i f i c a n t l y i n c r e a s e d a t t h e m i l k - r i p e s t a g e (10 t o 15 days a f t e r h e a d i n g ) by treatment w i t h BR under both c o n d i t i o n s . L e v e l s o f endogenous IAA and ABA i n g r a i n s a t 10 and 15 days a f t e r h e a d i n g were determined by HPLC and E L I S A , r e s p e c t i v e l y . E t h y l e n e from p a n i c l e s was determined by GC. I n g r a i n s o b t a i n e d from greenhouse e x p e r i m e n t s a t 10 and 15 days a f t e r h e a d i n g , BR t r e a t m e n t i n c r e a s e d the l e v e l o f IAA b u t , i n c o n t r a s t , decreased the l e v e l o f ABA ( T a b l e I I ) . In g r a i n s o b t a i n e d from p h y t o t r o n e x p e r i m e n t s , BR t r e a t m e n t decreased both the l e v e l s o f IAA and ABA at 10 days a f t e r h e a d i n g , w h i l e it


27. FUJII ET AL.

200

309


(Phytotron 20°C/13°C) FLS 200 2LS

r

r

• BR 0 ppm • BR 10"ppm M BR 10 ppm 3

g

150

150

*-

100

100

_2


50

0 Weeks after Heading (Greenhouse) 100 FLS 100 2LS 100 3LS r

~

50

r

50

'ill 1 1 £

r

M

[k

f k . .111 n -

Weeks after Heading

Figure 1. E f f e c t of Brassinolide on Starch Content i n Leaf Sheath of Rice Plants. FLSrflag leaf sheath, 2LS:2nd l e a f sheath, 3LS:3rd leaf sheath.

Figure 2. E f f e c t of Brassinolide on Total Starch Content i n Panicles of Rice Plants.


BRASSINOSTEROIDS: CHEMISTRY, BIOACTIVITY, AND APPLICATIONS

310

i n c r e a s e d b o t h the l e v e l s o f IAA and ABA a t 15 days a f t e r heading ( T a b l e I I ) . E t h y l e n e e v o l u t i o n from p a n i c l e s a t the m i l k - r i p e s t a g e i n c r e a s e d by BR t r e a t m e n t ( T a b l e I I I ) under greenhouse c o n d i t i o n s . I t is d i f f i c u l t , from t h e s e r e s u l t s , t o a s c e r t a i n the r e l a t i o n o f the change i n t h e s e p l a n t hormone l e v e l s i n d u c e d by BR t o g r a i n d e v e l o p ment. However, endogenous l e v e l s o f IAA and ABA i n p a n i c l e s were much h i g h e r t h a n those i n v e g e t a t i v e t i s s u e ( 3 - 4 ) , s u g g e s t i n g t h a t these Table I I .

Effect

of Brassinolide

on IAA and ABA Levels

i n Grains

0


under Greenhouse and Phytotron (22 C/17°C) Conditions BR (ppm)

0 10~

3

Greenhouse Days a f t e r heading 10 15 IAA ABA IAA ABA

Phytotron (22°C/17°C) Days a f t e r heading 10 15 IAA ABA IAA ABA

(ng/g fwt) 670 155

(ng/g fwt) 1360 350

(ng/g fwt) 530 151

(ng/g fwt) 1140 213

840

1535

450

1610

125

165

113

270

Table I I I . E f f e c t of Brassinolide on Ethylene Evolution from Panicles under Greenhouse Conditions BR

Ethylene

(ppm)

evolution

(nl/g fwt/24h) Days a f t e r heading

0 IO"

3

15 9.7

20 3.9

12.5

6.4

p l a n t hormones may r e g u l a t e the development o f s e e d s . A c c o r d i n g l y , the changes of the b a l a n c e o f t h e s e l e v e l s i n d u c e d by BR may be a s s o c i a t e d w i t h promotion o f the t r a n s l o c a t i o n o f p h o t o s y n t h e t i c p r o d u c t s i n p a n i c l e s and a l s o a c c u m u l a t i o n o f the s t a r c h i n g r a i n s . Much more i n f o r m a t i o n i s needed t o e s t a b l i s h u n e q u i v o c a l l y a r e l a t i o n s h i p between t h e changes o f t h e p l a n t , hormones brought about by BR and t h e promo t i o n o f g r a i n g r o w t h . A l s o , i n v e s t i g a t i o n f o r the c o n t e n t s o f BR and o t h e r hormones i n g r a i n s d u r i n g the r i p e n i n g p e r i o d and the enzyme a c t i v i t i e s g o v e r n i n g c a r b o h y d r a t e m e t a b o l i s m may be needed. Acknowledgment. We w i s h t o thank D r . S. Watanabe, I n s t i t u t e of A g r o b i o l o g i c a l R e s o u r s e s , f o r h e l p f u l d i s c u s s i o n s about the endogenous p l a n t hormone a n a l y s e s . L i t e r a t u r e Cited (1) L u o , B.; Kumura, 55 , 2 9 1 .

A.;

Ishii,

R . ; Wada, J. Japan. J. Crop Sci. 1986,


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(2) Hamada, K.; Nishi, S.; Uezono, T.; Fujiwara, S.; Nakazawa, Y. Abstract of papers of the 12th International Conference on Plant Growth Substances (Heidelberg) 1985, 43. (3) Kobayashi, M.; Sakurai, A.; Saka, H.; Takahashi, N. Agric. Biol. Chem. 1989, 53, 1089. (4) Suzuki, Y.; Kurogouchi, S,; Murofushi, N.; Ota, Y.; Takahashi, N. Agric. Biol. Chem. 1981, 22, 1085. 13,

1991


R E C E I V E D May


Growth-Regulating Action of Brassinolide in Rice Plants - American

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