Laboratory and Field Evaluation of Bioregulators - ACS Publications

3 Laboratory and Field Evaluation of Bioregulators C. A. S T U T T E

Downloaded by UNIV OF ARIZONA on April 5, 2017 | http://pubs.acs.org Publication Date: July 6, 1984 | doi: 10.1021/bk-1984-0257.ch003

Department of Agronomy, Altheimer Laboratory, University of Arkansas, Fayetteville, A R 72701

In recent years a great deal of attention has been given to chemical control of physiological processes in plants. S c i e n t i s t s have joined efforts to understand plant regulation in such organizations as the Plant Growth Regulator Society of America and the British Plant Growth Regulator Group. Proceedings and other publications from such organizations illustrate and h i g h l i g h t the extensive and intensive work that i s being done with growth regulators ( 1 , 3 ) . Most important perhaps i s the use of plant bioregulators to increase food supplies of the world. Recent l i t e r a t u r e i l l u s t r a t e s our present c a p a b i l i t i e s for regulating crop plant growth and enhancing yields (e.g. 2). Technological developments i n bioregulation are many. We know that bioregulators are capable of a l t e r i n g genetic potentials by modifying biochemical and physiological processes. By a l t e r i n g phys i o l o g i c a l processes with bioregulators, we may be affording the plant the means to r e s i s t or overcome environmental or b i o l o g i c a l stresses and may, thereby, contribute to enhanced y i e l d s . However, it i s necessary to transfer t h i s bioregulation technology to the farmer so that his crop production and management can benefit from the technology. To make t h i s transfer, the physiology of a s p e c i f i c crop and the c h a r a c t e r i s t i c s of bioregulators need to be managed as a part of the overall system of crop management. It i s the purpose of this paper to convey to the reader the concept of using both laboratory and field evaluations to aid i n developing needed information for using bioregulators i n crop physiology/ management. Each crop must have special considerations not only because of c u l t i v a r variations but because the interactions with the various environments must be understood. A physiological understanding of a s p e c i f i c crop requires information inputs from laboratory and field experiments. Our objective has been to develop physiological laboratory methods that will provide information to plan and carry out field tests so that we may predict plant responses. This information should improve our c u l t u r a l practices with p o s i t i v e planning and the selection of v a r i e t i e s and practices that will provide the best performance under s p e c i f i c growing conditions. Many chemicals have been introduced into laboratory and field 0097-6156/84/0257-0023$06.00/0 © 1984 American Chemical Society

Ory and Rittig; Bioregulators ACS Symposium Series; American Chemical Society: Washington, DC, 1984.

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BIOREGULATORS: C H E M I S T R Y A N D USES

e v a l u a t i o n programs to d e t e r m i n e t h e i r p o t e n t i a l u t i l i t y i n crop production. Most of the c h e m i c a l s t e s t e d i n f i e l d p l o t s were s e l e c t e d on the b a s i s of t h e i r a c t i v i t y i n s p e c i f i c laboratory tests. Chemicals t h a t do not show response i n the l a b o r a t o r y t e s t s a r e dropped from f u r t h e r c o n s i d e r a t i o n . T h i s s e l e c t i v e p r o c e s s e l i m i n a t e s a l a r g e number of c h e m i c a l s from the more e x p e n s i v e and t i m e - c o n s u m i n g f i e l d e v a l u a t i o n programs. The e f f e c t i v e use of bioregulators i n crop p r o d u c t i o n may r e q u i r e t h a t many c u r r e n t c u l t u r a l p r a c t i c e s be r e - e v a l u a t e d . Some new p r a c t i c e s may have t o be adapted i n o r d e r t o a c h i e v e maximum p r o d u c t i v i t y .


L a b o r a t o r y Techniques

for

Evaluation

S i n c e i t i s v e r y e x p e n s i v e and time consuming to e v a l u a t e c h e m i c a l s t h a t are a v a i l a b l e and t h a t c o u l d be u s e f u l i n crop p r o d u c t i o n , i t becomes n e c e s s a r y to develop r e s e a r c h methods to o b t a i n d a t a which can r a p i d l y i d e n t i f y p o t e n t i a l l y u s e f u l c h e m i c a l s and p r o v i d e d a t a on how they may b e s t be u t i l i z e d . Over the p a s t few y e a r s much r e s e a r c h a t t e n t i o n has been d i r e c t e d to d e v e l o p i n g and u t i l i z i n g l a b o r a t o r y methods to e v a l u a t e p h y s i o l o g i c a l responses to s y n t h e t i c c h e m i c a l s . In o r d e r to reduce the v a r i a b i l i t y between p l a n t s i n t e s t s , our e v a l u a t i o n s are made u s i n g p r i m a r i l y soybean t i s s u e from s i n g l e p l a n t seed s o u r c e s . T h i s a l l o w s f o r l e s s t e s t v a r i a b i l i t y by p r o v i d i n g a h i g h degree of g e n e t i c u n i f o r m i t y and a l s o m i n i m i z i n g v a r i a b i l i t y due to s p e c i f i c environments at the p r o d u c t i o n s i t e . The f o l l o w i n g s e r i e s of t e s t s are p r e s e n t l y b e i n g u t i l i z e d f o r e v a l u a t i o n of p h y s i o l o g i c a l responses induced by e x p e r i m e n t a l b i o r e g u l a t o r s b e f o r e e x t e n s i v e e v a l u a t i o n under f i e l d c o n d i t i o n s . Other t e s t s may a l s o be u s e d . T h i s s e r i e s i s used t o i l l u s t r a t e the potential. O2 e v o l u t i o n 14

C02 f i x a t i o n

w a t e r uptake nitrate

uptake

p o t a s s i u m uptake transpiration

rates

n i t r o g e n l o s s from p l a n t f o l i a g e and temperature e f f e c t s on Ν l o s s ethylene evolution leaf tissue

from

p h e n o l i c s and p h e n o l i c g l y c o s i d e s ( t o t a l and composition) field yield

response.


STUTTE

25

Laboratory and Field Evaluation

O2 E v o l u t i o n - CO2 F i x a t i o n T h i s l a b o r a t o r y t e s t h e l p s t o c l a s s i f y a chemical as t o i t s e f f e c t on a) i n c r e a s i n g , b) d e c r e a s i n g , or c) h a v i n g no e f f e c t on t h e * C02 f i x a t i o n p r o c e s s e s i n v o l v e d i n p h o t o s y n t h e s i s and i t s consequent e f f e c t on O2 e v o l u t i o n p r o c e s s e s . Many q u e s t i o n s can be answered w i t h t h i s t e s t : a) A r e t h e p r o c e s s e s o f CO2 f i x a t i o n and O2 e v o l u t i o n dependent upon each o t h e r ? b) Can the CO2 f i x a t i o n be i n c r e a s e d w h i l e t h e O2 e v o l u t i o n i s b e i n g decreased? U s i n g t h i s a p p r o a c h , we have i d e n t i f i e d c h e m i c a l s t h a t i n c r e a s e * C02 f i x a t i o n w h i l e r e d u c i n g O2 e v o l u t i o n by 20 t o 40 p e r cent. T h i s may be due t o the reduced l e v e l s o f O2 i n t e r n a l l y t h a t reduce O2 c o m p e t i t i o n w i t h CO2 a t the s i t e o f t h e enzyme a c t i v i t y which i s i n v o l v e d i n CO2 f i x a t i o n . T h i s would assume t h a t CO2 f i x a t i o n i s not a major l i m i t i n g f a c t o r t o h i g h crop y i e l d , but t h a t the h i g h l e v e l o f O2 i n t h e t i s s u e g r e a t l y i n c r e a s e s o x i d a t i o n o f a s s i m i l a t e s t h a t reduce y i e l d p o t e n t i a l s . T h e r e f o r e , one may be l o o k i n g f o r a c h e m i c a l t h a t reduces o x i d a t i o n by lower O2 p r o d u c t i o n i n t h e t i s s u e when i n l i g h t , and t h i s can be measured by O2 e v o l u t i o n , w h i l e i n c r e a s i n g CO2 f i x a t i o n o r having no e f f e c t on t h e p r o cess. I f a c h e m i c a l i n h i b i t s both O2 e v o l u t i o n and CO2 f i x a t i o n , i t may be a c a n d i d a t e f o r a h e r b i c i d e , o r some o t h e r use as a h a r v e s t a i d , but i s not l i k e l y t o be u s e f u l as a crop y i e l d enhancer. When a c h e m i c a l shows p o t e n t i a l i n t h i s t e s t , i t may be f u r t h e r e v a l u a t e d as t o i t s e f f e c t s on o t h e r p r o c e s s e s . 4


4

W a t e r , N i t r a t e , and P o t a s s i u m Uptake C h e m i c a l s t h a t would have p o t e n t i a l as y i e l d enhancers would p r o b a b l y have l i t t l e e f f e c t on r e d u c i n g water and n u t r i e n t uptake by the r o o t s . I f so they would be p r i m a r i l y used i n e a r l y v e g e t a t i v e growth stages o r as h a r v e s t a i d s i n such c r o p s as sugar cane t o i n c r e a s e sucrose production p r i o r to h a r v e s t . U s i n g p l a n t s from a s i n g l e p l a n t seed s o u r c e , one can e v a l u a t e the e f f e c t s o f chemical t r e a t m e n t on these p r o c e s s e s i n a c o n t r o l l e d environment chamber. The p l a n t s ( s o y b e a n s , f o r example) a r e grown i n hydroponic n u t r i e n t m e d i a , and a t t h e time o f t r e a t m e n t (V4 or R l s t a g e ) t h e n u t r i e n t media w i t h known c o n c e n t r a t i o n o f elements a r e m o n i t o r e d f o r amounts and r a t e s o f uptake o f w a t e r , n i t r a t e s , and p o t a s s i u m . O t h e r elements can a l s o be m o n i t o r e d . In soybeans, i f a chemical reduces t h e uptake o f p o t a s s i u m , i t i s n o t l i k e l y t o be u s e f u l f o r a p p l i c a t i o n d u r i n g p o d - f i l l ; however, i t may be u s e f u l during e a r l y vegetative stages to conserve s o i l potassium i n the r o o t zone f o r use d u r i n g t h e r e p r o d u c t i v e growth s t a g e s . I f a chemi c a l reduces water uptake w i t h o u t g r e a t l y a f f e c t i n g o t h e r i m p o r t a n t p h y s i o l o g i c a l f u n c t i o n s , i t may be u s e f u l i n i n c r e a s i n g e f f i c i e n c y of water u t i l i z a t i o n . A chemical t h a t reduces n i t r a t e uptake but s t i l l induces g r e a t e r p r o d u c t i o n o f d r y m a t t e r may be u s e f u l i n increasing nitrogen u t i l i z a t i o n e f f i c i e n c y with higher grain y i e l d s . N i t r o g e n Loss from P l a n t F o l i a g e With the d i s c o v e r y t h a t n i t r o g e n i s l o s t from p l a n t f o l i a g e w i t h t r a n s p i r a t i o n and t h e u t i l i z a t i o n o f a p y r o - c h e m i l u m i n e s c e n t method f o r a n a l y z i n g t h e amounts o f n i t r o g e n i n reduced and o x i d i z e d f o r m s ,



26

BIOREGULATORS: C H E M I S T R Y A N D USES

another l a b o r a t o r y method has been added to c o l l e c t u s e f u l d a t a . T h i s n i t r o g e n d i s s i p a t i o n t h a t i s c o l l e c t e d i n a tube p l a c e d i n dry i c e has been c o r r e l a t e d d i r e c t l y w i t h temperature and t r a n s p i r a t i o n . The n i t r o g e n l o s s i s g r e a t e r i n s e n e s c i n g and s t r e s s e d t i s s u e . Chemicals may be i d e n t i f i e d t h a t w i l l reduce the n i t r o g e n l o s s a t h i g h temperatures (35 C and g r e a t e r ) and i n c r e a s e crop y i e l d s by more e f f i c i e n t u t i l i z a t i o n of a v a i l a b l e n i t r o g e n . The u t i l i z a t i o n of n i t r o g e n i n p l a n t s i n v o l v e s many high energy-consuming p r o c e s s e s . I f t h i s energy i s conserved r a t h e r than l o s t from the f o l i a g e , p r o d u c t i o n c e r t a i n l y c o u l d be s i g n i f i c a n t l y i n c r e a s e d . However, the r e s e a r c h e r must be aware t h a t the l o s s of n i t r o g e n from the f o l i a g e w i t h t r a n s p i r a t i o n may be a l s o a d e f e n s i v e p r o c e s s t o p r o t e c t the t i s s u e from a c c u m u l a t i n g t o x i c c o n c e n t r a t i o n s t h a t c o u l d be f a t a l t o the p l a n t . Ethylene Evolution

from L e a f

Tissue

When most p l a n t s are s u b j e c t e d t o s t r e s s c o n d i t i o n s , the p r o d u c t i o n of e t h y l e n e i s i n c r e a s e d . E t h y l e n e has been shown to a f f e c t many physiological processes. Therefore, the c o n d i t i o n s that a l t e r e t h y l e n e p r o d u c t i o n may be u s e f u l i n f o r m a t i o n i n e v a l u a t i n g responses t o chemicals. Over the l a s t f o u r y e a r s many o r g a n i c compounds have been e v a l u a t e d u s i n g a r a p i d method t h a t u t i l i z e s l e a f d i s c t i s s u e from p l a n t s having a s i n g l e parent seed s o u r c e . The l e a f d i s c s are s u b merged i n the e x p e r i m e n t a l t e s t s o l u t i o n f o r a p p r o x i m a t e l y 20 m i n u t e s , a f t e r which they are r i n s e d w i t h d e i o n i z e d water and r a p i d l y b l o t t e d , then p l a c e d i n t o a 4 - c c v i a l , and s e a l e d w i t h a serum stopper. A f t e r d i f f e r e n t i n t e r v a l s , samples are removed f o r e t h y lene determinations. The e t h y l e n e i s r e p o r t e d as μ ΐ ethylene/ liter/cm^/hr. T h i s l a b o r a t o r y method, which i s r a p i d and a l l o w s f o r many c h e m i c a l s to be e v a l u a t e d , has i d e n t i f i e d compounds t h a t s t i m u l a t e e t h y l e n e e v o l u t i o n as w e l l as i n h i b i t e t h y l e n e evolution. Compounds are s e l e c t e d t h a t s t i m u l a t e d e t h y l e n e e v o l u t i o n i n both l i g h t and dark as w e l l as a t h i g h and low temperatures f o r f i e l d e v a l u a t i o n as s t i m u l a t o r s of c o t t o n b o l l o p e n i n g . The p o t e n t i a l f o r u t i l i z a t i o n of t h i s type i n f o r m a t i o n about c h e m i c a l s t h a t s t i m u l a t e and i n h i b i t e t h y l e n e p r o d u c t i o n are many and can be u s e f u l i n many crop p r o d u c t i o n p r a c t i c e s . 4

P h e n o l i c s and P h e n o l i c G l y c o s i d e s P h e n o l i c s were once c o n s i d e r e d as waste p r o d u c t s ; however, they are now r e c o g n i z e d as very i m p o r t a n t to the growth and w e l l - b e i n g o f plants. P h e n o l i c s may be i n v o l v e d i n the r e s i s t a n c e phenomenon o f p l a n t s to various p e s t s . The p h e n o l i c c o n s t i t u e n t s p r e s e n t and those produced a t the time and a t the s i t e of i n v a s i o n are both thought t o i n f l u e n c e p e s t r e s i s t a n c e . The i n f l u e n c e t h a t p h e n o l i c c o n s t i t u e n t s have on enzyme a c t i v i t i e s w i t h i n the p l a n t a l s o i s of great importance. C h e m i c a l s are a p p l i e d t o p l a n t s grown i n c o n t r o l l e d environmen t a l chambers from s i n g l e p l a n t seed s o u r c e s . Seven days a f t e r t r e a t m e n t comparable l e a f t i s s u e i s analyzed f o r p h e n o l i c com p o s i t i o n by high p r e s s u r e l i q u i d chromatography. Chemicals i d e n t i f i e d may a l t e r p h e n o l i c metabolism and, c o n s e q u e n t l y , s u s c e p -


3. S T U T T E

Laboratory and Field Evaluation

27

tibility or r e s i s t a n c e to s p e c i f i c pests. There a r e many i m p l i c a t i o n s o f t h e p h y s i o l o g i c a l - b i o c h e m i c a l i n t e r a c t i o n s as they are r e l a t e d to applied a g r i c u l t u r e .


F i e l d Test

Evaluations

C o r r e l a t e d w i t h laboratory t e s t s are f i e l d t e s t p l o t s . Field plots a r e put out each y e a r t o e v a l u a t e chemical t r e a t m e n t responses i n f i e l d s using d i f f e r e n t c u l t u r a l p r a c t i c e s . The c h e m i c a l s t e s t e d i n the f i e l d p l o t s are s e l e c t e d because o f t h e i r s p e c i f i c a c t i v i t y i n the l a b o r a t o r y t e s t s . Many o f t h e supplementary o b s e r v a t i o n s i n f i e l d s t u d i e s may suggest t h a t t h e e f f e c t i v e n e s s o f a b i o r e g u l a t o r will r e q u i r e m o d i f i c a t i o n o f many o f our c u l t u r a l practices, v a r i e t i e s , row s p a c i n g , s e e d i n g r a t e s , p l a n t i n g d a t e s , p e s t i c i d e treatments, f e r t i l i z e r programs, i r r i g a t i o n p r a c t i c e s , and crop r o t a t i o n s c h e d u l e s , a l l o f which seem t o be i n v o l v e d i n s u c c e s s f u l use o f b i o r e g u l a t o r s . One must r e a l i z e t h a t , i n a d d i t i o n , t h e c h e m i c a l s themselves need t o be f u r t h e r t e s t e d i n o r d e r t o d e t e r m i n e the best c o m b i n a t i o n i n f o r m u l a t i o n , r a t e , time o f a p p l i c a t i o n , spray volume, spray equipment, and s u r f a c t a n t o r a d j u v a n t t h a t w i l l r e s u l t i n t h e g r e a t e s t economic r e t u r n and p r o v i d e environmental protection. Summary The advantages of s u b j e c t i n g a p o t e n t i a l a g r i c u l t u r a l c h e m i c a l t o l a b o r a t o r y e v a l u a t i o n b e f o r e f i e l d t e s t i n g a r e many: 1) A s m a l l amount of chemical i s n e c e s s a r y f o r the t e s t s ; 2) c o s t s can be reduced by e l i m i n a t i n g from f u r t h e r t e s t i n g c h e m i c a l s t h a t have h i g h p r o b a b i l i t y of not w o r k i n g ; 3) l a b o r a t o r y t e s t s can i d e n t i f y t h e p o s s i b l e r a t e of the c h e m i c a l necessary t o b r i n g about a s p e c i f i c response i n f i e l d c o n d i t i o n s ; 4) t h e s e t e s t s can h e l p t o p r e d i c t t h e crop and t h e time o f t r e a t m e n t most l i k e l y t o s u c c e e d ; 5) they can p r o v i d e a s t o r e h o u s e o f d a t a on p l a n t responses t o c h e m i c a l s t h a t can be u s e f u l when a d d i t i o n a l s c i e n t i f i c d i s c o v e r i e s a r e advanced; 6) they p r o v i d e chemical s t r u c t u r e - p l a n t response r e l a t i o n s h i p s t h a t can be u s e f u l i n t h e s y n t h e s i s of c h e m i c a l s t o induce a d e s i r e d r e s p o n s e ; and 7) t h e s e t e s t s reduce t h e time and c o s t o f p r o d u c t development w i t h a h i g h e r l e v e l o f s a f e t y t o t h e p u b l i c by r e d u c i n g the quantity of chemicals necessary for experimentation. The p o t e n t i a l f o r u t i l i z a t i o n o f b i o r e g u l a t i n g c h e m i c a l s i s large. However, much i n f o r m a t i o n i s needed on p h y s i o l o g i c a l r e sponse b e f o r e crop p r o d u c t i o n can e f f i c i e n t l y u t i l i z e a program by which p h y s i o l o g i c a l responses a r e managed w i t h b i o r e g u l a t i n g c h e m i cals. Growers and r e s e a r c h e r s must cease t o look f o r m i r a c l e s and s e a r c h f o r means by which p h y s i o l o g i c a l p r o c e s s e s can be enhanced o r i n h i b i t e d t o s i g n i f i c a n t l y i n c r e a s e y i e l d s o r a s s i s t i n crop p r o d u c tion. We know t h a t t h e g e n e t i c p o t e n t i a l i s p r e s e n t i n o u r commonly produced crop c u l t i v a r s ; however, this potential i s not b e i n g achieved with our present c u l t u r a l p r a c t i c e s . With t h e use of b i o r e g u l a t o r s as p h y s i o l o g i c a l managers, we can g r e a t l y improve our p o t e n t i a l f o r i n c r e a s i n g e f f i c i e n c y of s e v e r a l p h y s i o l o g i c a l p r o c e s s e s and i n c r e a s e crop y i e l d s . The p o t e n t i a l s a r e g r e a t . We must not n e g l e c t t h e needed r e s e a r c h t h a t can p r o v i d e expanded p r o d u c t i o n around the w o r l d .


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B I O R E G U L A T O R S : C H E M I S T R Y AND U S E S

L i t e r a t u r e Cited 1. 2. 3.

B r i t i s h Plant Growth Regulator Group Proceedings, B u l l e t i n s and Monograph, 1979 through 1983. N i c k e l l , Louis G. (ed.) 1983. Plant Growth Regulating Chemicals V o l . I and I I . CRC Press I n c . , Boca Raton, FL. Plant Growth Regulator Proceedings, Handbooks and B u l l e t i n s , 1975 through 1983. Publications of the Plant Growth Regulator Society of America.


RECEIVED April 4, 1984


Laboratory and Field Evaluation of Bioregulators - ACS Publications

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