Peroxidizing Herbicides - ACS Symposium Series (ACS Publications)

Chapter 28

Peroxidizing Herbicides Some Aspects on Tolerance

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on April 15, 2016 | http://pubs.acs.org Publication Date: February 23, 1990 | doi: 10.1021/bk-1990-0421.ch028

Gerhard Sandmann and Peter Böger Lehrstuhl für Physiologie und Biochemie der Pflanzen, Universität Konstanz, D-7750 Konstanz, Federal Republic of Germany

Destruction of plant membranes, pigments and other cell constituents occurs in the presence of "peroxidizing herbicides" like p-nitrodiphenyl ethers (1), lutidine derivatives (2) or cyclic imides (3); some structures are given in Figure 1. Such compounds are grouped as a particular class of xenobiotics because - in contrast to bipyridylium ions like paraquat - they do not operate as (artificial) terminal electron acceptors in photosynthetic electron transport. Secondly, they do not cause a light-induced oxygen uptake stoichiometrically linked to electron transport and thirdly, their mode of action is connected with interference of chlorophyll biosynthesis.*) Measurement of ethane formation has been used to quantitate peroxidation especially with higher-plant cell cultures and microalgae. Molecular oxygen reacts with polyunsaturated fatty-acid radicals to form radical intermediates and peroxides. Figure 2 explains assumed chains of events leading to short-chain hydrocarbons from polyunsaturated fatty acids. The chain length of peroxidatively formed alkane species (together with small amounts of alkenes) depends on the nature of the fatty acids occurring in the membranes. As was established in our laboratory the chain length of short-chain (gaseous) hydrocarbons formed is ω- 1 (7). Radicals and/or activated oxygen initiate the herbicide-induced degradations in the cells (8). Electron spin-resonance signals can be found by illuminating isolated thylakoids from higher plants treated with peroxidizing compounds provided spin-trap techniques are applied. Photosystem-II inhibitors may alleviate peroxidation in photosynthetic cells (e.g. [1,9]). Some light-induced oxygen uptake was observed with higher concentrations of a peroxidizing diphenyl ether (10), but neither substantial formation of peroxide (11) nor superoxide was *) Only selected references are cited. For more detailed overviews the reader may consult (4,5,6). 0097-6156/90/0421-0407$06.00/0 © 1990 American Chemical Society

Green et al.; Managing Resistance to Agrochemicals ACS Symposium Series; American Chemical Society: Washington, DC, 1990.


408

MANAGING

0 Chlorophthalim

Oxyfluorfen

RESISTANCE TO AGROCHEMICALS

Oxadiazon

LS 82-556 (S-form)

F i g u r e 1. C h e m i c a l s t r u c t u r e s o f f o u r t y p i c a l p e r o x i d i z i n g compounds: c h l o r o p h t h a l i m , N - ( 4 - c h l o r o p h e n y l ) - 3 , 4 , 5 , 6 tetrahydrophthalimide; oxadiazon, 3-(2,4-dichloro-5isopropoxyphenyl)-5-tert-butyl-l,3,4-oxadiazol-2(3Ip-one; oxyfluorfen, 2-chloro-4-(trifluoromethyl)phenyl-3-ethoxy - 4 - n i t r o p h e n y l e t h e r ; LS 82-556, ( S ) 3 - N - ( m e t h y l b e n z y l ) carbamoyl-5-propionyl-2,6-lutidine. Also 2,4,5-phenylsubstituted p y r i m i d i n e d i o n e s e x h i b i t p e r o x i d i z i n g a c t i v i t y , e.g. 3-(4-chloro-5-ethoxy-2-fluorophenyl)-l-methyl-6-(trifluoromethyl) -2,4(lH,3H)pyrimidinedione (34).



28.

SANDMANNANDBOGER

Peroxidizing Herbicides

d e t e c t e d ( 1 ) . S i n g l e t oxygen was shown t o be g e n e r a t e d i n the l i g h t by i s o l a t e d t h y l a k o i d s and a p p a r e n t l y no p h o t o s y n t h e t i c e l e c t r o n t r a n s p o r t was r e q u i r e d ( 1 2 ) . G e n e r a l l y , l i g h t i s needed f o r " a c t i v a t i o n " o f p e r o x i d i z i n g h e r b i c i d e s . There i s , however, a l s o p h y t o t o x i c a c t i v i t y t a k i n g p l a c e i n the d a r k ( 1 3 ) , and the b a s i s f o r t h i s i s not y e t u n d e r s t o o d . As shown by a r e c e n t s t u d y , c e l l s can e v o l v e s u b s t a n t i a l ethane i n the dark a f t e r p r e i l l u m i n a t i o n f o r some hours w i t h p e r o x i d i z i n g compounds p r e s e n t (unpubl. r e s u l t s ) . U s i n g v a r i o u s t e t r a h y d r o p h t h a l i m i d e s a c o m p a r a t i v e study demonstrated t h a t growth and c h l o r o p h y l l c o n t e n t o f b o t h h e t e r o t r o p h i c (dark-grown) and a u t o t r o p h i c ( l i g h t - g r o w n ) Scenedesmus a c u t u s were i n h i b i t e d showing the same s t r u c t u r e - a c t i v i t y r e l a t i o n s h i p . Furthermore, t h i s r e l a t i o n s h i p was found i d e n t i c a l w i t h a r o o t - g r o w t h i n h i b i t i o n assay ( E c h i n o c h l o a u t i l i s ) and w i t h the greenhouse pot t e s t as w e l l u s i n g d i f f e r e n t weeds ( 1 3 ) . O b v i o u s l y , an i d e n t i c a l b a s i c p h y t o t o x i c mechanism i s i n s t r u m e n t a l i n the l i g h t and the d a r k which has not been c l a r i f i e d at the moment. The l i g h t - d e p e n d e n t mechanism(s) as to how the s t a r t i n g r a d i c a l s f o r p e r o x i d a t i o n are formed i s not y e t e l u c i d a t e d . I n a e r o b i c a l k a l i n e s o l u t i o n s p h o t o r e d u c t i o n by v i s i b l e l i g h t o f n i t r o d i p h e n y l ethers to ESR-detectable r a d i c a l s u s i n g 3-carotene as s e n s i t i z e r was r e p o r t e d r e c e n t l y ( 1 4 ) . W i t h p r o t o p o r p h y r i n IX and an a p p r o p r i a t e r e d u c t a n t i t c o u l d be demonstrated t h a t o n l y n i t r o d i p h e n y l e t h e r s , not the p - c h l o r o a n a l o g s , l e d t o l i g h t - i n d u c e d r a d i c a l s a l t h o u g h the c h l o r o a n a l o g s e x h i b i t e d s t r o n g p e r o x i d a t i o n a c t i v i t y ( u n p u b l . r e s u l t s of our l a b o r a t o r y ) . A c c o r d i n g l y , d i r e c t f o r m a t i o n of d i p h e n y l e t h e r r a d i c a l s i s not an e s s e n t i a l s t e p . The a c t i o n s p e c t r a f o r p h y t o t o x i c i t y were r e p o r t e d w i t h maxima at 450 and 670 nm ( u s i n g Chlamydomonas and d i p h e n y l e t h e r s ) i n d i c a t i v e o f c a r o t e n o i d s and c h l o r o p h y l l s as p o s s i b l e p h o t o r e c e p t o r s ( 1 5 ) . Peaks a t 550 and 650 nm and a minor one a t 450 nm were found when Cucumis s a t i v u s was used, which were a l s o seen i n the p r e s e n c e of d i u r o n . In n o n - c h l o r o p h y l l o u s t i s s u e (grown i n f a r - r e d l i g h t ) the peak a t 450 nm was l o s t ( 1 6 ) . The a u t h o r s suggest a m u l t i p l e p h o t o r e a c t i o n , one p h o t o r e c e p t o r b e i n g c h l o r o p h y l l o r a r e l a t e d pigment. T h i s l a t t e r a c t i o n spectrum r e p o r t e d was observed by treatment w i t h the t e t r a h y d r o p h t h a l i m i d e S-23142, N-(4-chloro-2-fluoro-5-propargyloxyphenyl)-3,4,5,6t e t r a h y d r o p h t h a l i m i d e , as w e l l as w i t h the d i p h e n y l e t h e r a c i f l u o r f e n - m e t h y l , methyl 5 - [ 2 - c h l o r o - 4 - ( t r i f l u o r o m e t h y l ) phenoxy]-2-nitrobenzoate. However, the i n t e n s i t i e s o f the maxima of the a c t i o n s p e c t r a r e p o r t e d do not match w i t h the absorbance peaks of p r o t o p o r p h y r i n IX ( 1 7 ) . U s i n g n o n - c h l o r o p h y l l o u s soybean c e l l s the maximum p e r o x i d a t i o n a c t i v i t y was found between 350 and 450 nm, w i t h l e s s a c t i v i t y between 450 and 700 nm ( 1 8 ) . I t s h o u l d a l s o be mentioned t h a t a u t o t r o p h i c h e r b i c i d e - t r e a t e d Scenedesmus c e l l s w i t h no d e t e c t a b l e t e t r a p y r r o l e s p r e s e n t need s u b s t a n t i a l l y l e s s l i g h t i n t e n s i t y f o r p e r o x i d a t i o n than h e t e r o t r o p h i c c e l l s c o n t a i n i n g t e t r a p y r r o l e s (19). The p e r o x i d a t i v e response a g a i n s t h e r b i c i d e s can be d i f f e r e n t i n c e r t a i n s p e c i e s . F o r example, we f i n d t o l e r a n c e a g a i n s t o x y f l u o r f e n ( 2 0 ) . As shown i n F i g u r e 3, the m i c r o a l g a e Scenedesmus


409


B

102 '-^^ proto E >

1

-CX-lin-OOH

I /2 Formation of starter radical

^

4

Me

r

^

Me

2

o

2

2

OH" •

2

2

H0«

H0 • 0 041

2

2

CC-lin • HO • a - l i n . • H 0

HA

2

2 0 * 2H*

2

Proto IX • * 0 — proto K + 0 •

\

III Radical chain reaction r— a-lin • 0 —d-lin-00«(peroxy radical) (X-lin-00«*a-lin -d-lin-OOH *a-lin« Ai)-3-alkyl\ \ peroxide J

Me"* Me"* (X-lin-OOH ^ S ' a-lin-0»+ OH " a-lin-0»*O-lin KX-lin-OH •d-lin*

11

II Chain initiation

Q-lin + 102

i/l Direct formation of peroxo compound:

/

Peroxidation of a-linolenic acid

1) Proto E - ^ p r o t o K * 2) Proto K ^ p r o t o K*

II. Light reaction:

Interference with biosynthetic pathway, accumulation of protoporphyrin JK

I. Initial metabolic reaction:

1

Formation of02 or H O


Green et al.; Managing Resistance to Agrochemicals ACS Symposium Series; American Chemical Society: Washington, DC, 1990. 0

1

r

Me

r

2

CH CH . (ethyl radical)

/

CH0-CH=CH-R

(X-lin-O (U)-3-alkoxy radical)

F i g u r e 2: P e r o x i d a t i o n o f D o l y u n s a t u r a t e d f a t t y a c i d s e x e m p l i f i e d w i t h Oi - l i n o l e n i c a c i d ( = a - l i n ) . I n t h i s scheme r a d i c a l s a r e produced by t h e p r e s e n c e o f p r o t o p o r p h y r i n IX. I n t h e l i g h t , e i t h e r s i n g l e t oxygen may be g e n e r a t e d o r a s u p e r o x i d e a n i o n p r o v i d e d a s u i t a b l e redox r e a c t i o n o c c u r s i n case an a p p r o p r i a t e r e d u c t a n t i s a v a i l a b l e ( p a r t A I I , r e a c t i o n s 1,2). S i n g l e t oxygen may l e a d t o f o r m a t i o n o f a peroxo compounds ( o f a - l i n o l e n i c a c i d , p a r t B 1/1); t h e p r o t o p o r p h y r i n I X - r a d i c a l may form a hydroxy r a d i c a l HO* v i a s u p e r o x i d e , see p a r t 1/2 (41,42). B o t h , peroxo l i n o l e n i c a c i d and t h e hydroxy r a d i c a l w i l l i n i t i a t e a r a d i c a l c h a i n r e a c t i o n ( p a r t B, I I , I I I ) w i t h l i n o l e n i c a c i d l e a d i n g t o the G J - l i n r a d i c a l p o s s i b l y i n two ways as i n d i c a t e d by t h e arrows numbered (1) and ( 2 ) . T h i s r a d i c a l s u p p o r t s t h e c h a i n r e a c t i o n . The OL - l i n o l e n i c peroxo compound ( w - 3 - a l k y l p e r o x i d e ) c a n be degraded t o a l d e h y d e s and a l k a n e s w i t h some a l k e n e s (B IV) depending on t h e v a l e n c e s t a t e o f t h e m e t a l i o n s ( F e ) i n t h e c e l l (43,44). The f o r m a t i o n o f t h e s t a r t e r r a d i c a l ( s ) and t h e r a d i c a l c h e m i s t r y a t the p h o t o s e n s i t i z e d p o r p h y r i n s t i l l has t o be e x p e r i m e n t a l l y proven and i s h y p o t h e s i z e d by analogous r e a c t i o n s .

Me *

CX-lin-OOH

EZ Degradation of peroxo compound


MANAGING RESISTANCE TO AGROCHEMICALS


i

i

1

1

1

Incubation

i

1

time

i

i

i

(h)

F i g u r e 3. P e r o x i d a t i v e f o r m a t i o n o f s h o r t - c h a i n h y d r o c a r b o n s induced by o x y f l u o r f e n i n c u l t u r e s o f Scenedesmus (A) and B u m i l l e r i o p s i s ( B ) ; m o d i f i e d a f t e r ( 2 0 ) . p c v , t h e packed c e l l volume, r e f e r s t o the amount o f b i o l o g i c a l m a t e r i a l .



28. SANDMANNANDBOGER


413

and B u m i l l e r i o p s i s e x h i b i t d i f f e r e n t k i n e t i c s i n p e r o x i d a t i v e f o r m a t i o n o f h y d r o c a r b o n gases i n i t i a t e d by o x y f l u o r f e n . A f t e r o x y f l u o r f e n a p p l i c a t i o n b o t h response c u r v e s showed a l a g phase o f about 5 h f o r Scenedesmus o r 20 h f o r B u m i l l e r i o p s i s , a l t h o u g h t h e o x y f l u o r f e n c o n c e n t r a t i o n was 1 0 - f o l d h i g h e r i n t h e l a t t e r c u l t u r e . S a t u r a t i o n o f h y d r o c a r b o n f o r m a t i o n was reached approx. 30 h a f t e r t h e onset o f gas p r o d u c t i o n i n b o t h c a s e s . Uptake and i n c o r p o r a t i o n o f o x y f l u o r f e n i n t o t h e c e l l s was t h e same a f t e r 2 and 5 h i n Scenedesmus and 3 and 24 h i n B u m i l l e r i o p s i s . T h e r e f o r e , i t c a n be c o n c l u d e d t h a t t h e l a g phase i s not caused by slow o x y f l u o r f e n uptake b u t r a t h e r a c c o u n t s f o r t h a t p e r i o d an a n t i o x i d a t i v e system c a n cope w i t h p e r o x i d a t i o n b e f o r e i t i s o v e r t a x e d . D e t e r m i n a t i o n o f endogenous a s c o r b a t e has shown t h a t the t o l e r a n t B u m i l l e r i o p s i s c e l l s c o n t a i n 0.25 t o 0.3 ug a s c o r b a t e / u l packed c e l l volume, t h a t i s a 1 5 - f o l d h i g h e r l e v e l than i n Scenedesmus ( u n p u b l . d a t a ) . T h e r e f o r e , the o x y f l u o r f e n t o l e r a n c e , e x p r e s s e d as an extended l a g phase o f p e r o x i d a t i o n w i t h B u m i l l e r i o p s i s , c a n be e x p l a i n e d by i t s more e f f i c i e n t p r o t e c t i o n system a g a i n s t p e r o x i d a t i v e damage. V i c e v e r s a , p e r o x i d a t i o n c a n be speeded up by weakening t h e a n t i o x i d a t i v e system (see r e f . 21 f o r f u r t h e r d e t a i l s ) . I t should be n o t e d , however, t h a t a d i f f e r e n t p e r o x i d a t i v e response may a l s o be due t o d i f f e r e n t r a d i c a l f o r m a t i o n mechanisms. These mechanisms a r e s t i l l u n c l e a r (see F i g . 2 ) . No f l u o r e s c e n t t e t r a p y r r o l e s c o u l d be found i n Neurospora o r Phycomyces when grown i n t h e d a r k w i t h c h l o r o p h t h a l i m p r e s e n t (up t o 10 uM, 4 d a y s ) . I t has been demonstrated t h a t p e r o x i d i z i n g h e r b i c i d e s i n t e r f e r e w i t h t h e c h l o r o p h y l l b i o s y n t h e t i c pathway (22) by a c c u m u l a t i o n o f t e t r a p y r r o l e s (17,18,23,24). I t has a l s o been shown t h a t s o l u b l e p l a s t i d i c cytochrome d e c r e a s e s when o x a d i a z o n i s p r e s e n t i n a c o n c e n t r a t i o n when no p e r o x i d a t i o n i s y e t a p p a r e n t (25). F o r the i d e n t i f i c a t i o n o f the t e t r a p y r r o l e the t o l e r a n t B u m i l l e r i o p s i s was h e l p f u l . T h i s s p e c i e s e x c r e t e s l a r g e amounts of a t e t r a p y r r o l e i n t o t h e l i q u i d c u l t u r e medium when t r e a t e d w i t h p e r o x i d i z i n g h e r b i c i d e s l i k e oxadiazon, chlorophthalim, o x y f l u o r f e n , o r LS 82-556. The p r o d u c t found i n t h e medium c o u l d be i d e n t i f i e d by mass and NMR s p e c t r o m e t r y as p r o t o p o r p h y r i n IX (17). About 85% o f t h e p r o t o p o r p h y r i n IX accumulated by a u t o t r o p h i c c u l t u r e s o f B u m i l l e r i o p s i s was e x c r e t e d ( T a b l e I ) . The amount i n the c e l l i n c r e a s e d 5 - f o l d v s . c o n t r o l c e l l s . The e f f e c t o f p e r o x i d i z i n g h e r b i c i d e s on p r o t o p o r p h y r i n - I X a c c u m u l a t i o n by t h e s e n s i t i v e a l g a Scenedesmus was a l s o d e t e r m i n e d . T h i s s p e c i e s o f f e r s the advantage t o grow e i t h e r a u t o t r o p h i c a l l y i n t h e l i g h t or h e t e r o t r o p h i c a l l y i n t h e dark f o r m i n g c h l o r o p h y l l . I n c e l l s t r e a t e d w i t h 0.08 uM c h l o r o p h t h a l i m p r o t o p o r p h y r i n - I X l e v e l s were 15-times h i g h e r than i n t h e u n t r e a t e d c o n t r o l . No p r o t o p o r p h y r i n IX i n t h e c u l t u r e medium was found. I n ( a u t o t r o p h i c ) c e l l s grown i n t h e l i g h t p r o t o p o r p h y r i n IX c o u l d n e i t h e r be d e t e c t e d i n t h e c o n t r o l nor i n t r e a t e d c u l t u r e s (Table I ) , although these c e l l s are v e r y s e n s i t i v e a g a i n s t p e r o x i d i z i n g compounds. T e t r a p y r r o l e s may be degraded by p h o t o d e s t r u c t i o n b u t t h i s e x p l a n a t i o n remains t e n t a t i v e as y e t ( 1 9 ) .



414

MANAGING RESISTANCE TO

AGROCHEMICALS

Seemingly, under the i n f l u e n c e of p e r o x i d i z i n g h e r b i c i d e s i n h i g h e r p l a n t s p r o t o p o r p h y r i n IX a c t s as p h o t o s e n s i t i z e r i n i t i a t i n g p e r o x i d a t i o n as has been proposed ( [ 1 8 ] ; see e.g. r e f . 6 f o r o v e r v i e w ) . Treatment o f mung-bean s e e d l i n g s w i t h c h l o r o p h t h a l i m + gabaculine (the l a t t e r i n h i b i t s 6 - a m i n o l e v u l i n i c a c i d formation) p r e v e n t s the t o x i c e f f e c t of the h e r b i c i d e . M a l o n d i a l d e h y d e f o r m a t i o n i s s i m i l a r t o the c o n t r o l w h i l e the sample t r e a t e d w i t h chlorophthalim alone e x h i b i t e d a 100-fold higher l e v e l (unpubl. results). T a o p e l (26) suggested t h a t a s c o r b a t e w i l l reduce t o c o p h e r o x y l r a d i c a l s formed by f r e e - r a d i c a l r e a c t i o n ( s ) . C o n s e q u e n t l y , one Of - t o c o p h e r o l m o l e c u l e may scavenge many r a d i c a l s and s u b s e q u e n t l y stop p e r o x i d a t i o n ( 4 ) . The r a t i o of a s c o r b a t e t o OJ-tocopherol i s important f o r a p l a n t to p e r f o r m t o l e r a n c e a g a i n s t p e r o x i d i z e r s . A r a t i o o f a s c o r b a t e / QJ-tocopherol between 10:1 and 15:1 (wt/wt) i s e f f e c t i v e (see r e f . 27 and T a b l e I I , f i r s t t h r e e s p e c i e s ) . I t appears t h a t any r a t i o above o r below t h i s l e v e l i s c o r r e l a t e d w i t h reduced t o l e r a n c e a g a i n s t p e r o x i d a t i v e a t t a c k . The c a p a c i t y of the a n t i o x i d a t i v e system i s i n f l u e n c e d by r e d u c t i o n of d e h y d r o a s c o r b a t e t h r o u g h g l u t a t h i o n e , w h i c h i n t u r n i s reduced by NADPH g e n e r a t e d p h o t o s y n t h e t i c a l l y ( [ 2 1 ] , see the d a t a o f H a l l i w e l l assembled i n [ 2 8 ] ) . On the o t h e r hand, b i o s y n t h e s i s of a s c o r b a t e i s i m p o r t a n t , which i s c l o s e l y l i n k e d to the a s s i m i l a t o r y p a r t o f p h o t o s y n t h e s i s . T r e a t i n g bean l e a v e s ( P h a s e o l u s v u l g a r i s ) w i t h a c i f l u o r f e n , sodium 5 - [ 2 - c h l o r o 4-(trifluoromethylphenyl)phenoxy]-2-nitrobenzoate, increased p r o d u c t i o n of g l u t a t h i o n e and a s c o r b a t e as w e l l as the a c t i v i t i e s of g l u t a t h i o n e r e d u c t a s e and g a l a c t o n o l a c t o n e o x i d a s e ( t h e l a t t e r c a t a l y z i n g the l a s t s t e p i n the a s c o r b a t e - b i o s y n t h e s i s pathway) ( 2 9 ) . A p p a r e n t l y , p e r o x i d a t i o n w i l l become t o x i c , namely l e a d i n g to i r r e v e r s i b l e d e g r a d a t i o n s o f c e l l c o n s t i t u e n t s , i f the a n t i o x i d a t i v e system cannot cope w i t h the amount o f h e r b i c i d e - i n d u c e d r a d i c a l s . Such a s i t u a t i o n may e x p l a i n c o n t r o v e r s i a l f i n d i n g s , namely t h a t reduced g l u t a t h i o n e and the r e d u c t a s e a c t i v i t y ( o f cucumber d i s k s ) d e c r e a s e d a f t e r treatment w i t h a c i f l u o r f e n i n the l i g h t ( 3 0 ) . I n c r e a s e of a s c o r b a t e , g l u t a t h i o n e and a - t o c o p h e r o l was observed when spruce n e e d l e s were t r e a t e d w i t h s u l f u r d i o x i d e (31) w h i c h has been shown to i n d u c e p e r o x i d a t i o n (32, 33). E l e v a t e d l e v e l s of b o t h g l u t a t h i o n e r e d u c t a s e and s u p e r o x i d e dismutase were a l s o r e p o r t e d i n a mutant of Conyza b o n a r i e n s i s , t o l e r a n t a g a i n s t paraquat and a c i f l u o r f e n as w e l l ( 3 4 ) . I t needs t o be p o i n t e d out t h a t i n case of paraquat r e s i s t a n c e i n c r e a s e s i n g l u t a t h i o n e r e d u c t a s e and s u p e r o x i d e dismutase l e v e l s do not alone a d e q u a t e l y e x p l a i n t o l e r a n c e . G l u t a t h i o n e l e v e l s and s u p e r o x i d e dismutase a c t i v i t y was found even lower i n a p a r a q u a t - r e s i s t a n t Conyza b i o t y p e ( 3 5 ) . C o m p a r t m e n t a l i z a t i o n appears t o be an important f a c t o r s i n c e paraquat a p p a r e n t l y was n e i t h e r t r a n s p o r t e d i n t o the l e a v e s o f r e s i s t a n t b i o t y p e s (36) nor d i d i t r e a c h i t s s i t e o f a c t i o n i n the c h l o r o p l a s t (37,38). As demonstrated by F i g u r e 4 (comp. [33]) the g l u t a t h i o n e c o n t e n t o f bean l e a v e s can be m a n i p u l a t e d e i t h e r by a p p l y i n g d i f f e r e n t c o n c e n t r a t i o n s of o x o t h i a z o l i d i n e c a r b o x y l a t e - l e a d i n g to increase - or buthionine s u l f o x i m i n e , l e a d i n g to decrease of


28. SANDMANNANDBOGER


415

T a b l e I . F o r m a t i o n o f p r o t o p o r p h y r i n IX by B u m i l l e r i o p s i s and Scenedesmus i n t h e p r e s e n c e o f c h l o r o p h t h a l i m

Protoporphyrin Control


S p e c i e s / c u l t u r e type

(1) B u m i l l e r i o p s i s , a u t o t r o p h i c c e l l s , e x c r e t i o n i n t o medium

76.8 504.2

15.0 0

11

(2) Scenedesmus, a u t o t r o p h i c c e l l s , h e t e r o t r o p h i c c e l l s (dark) " , e x c r e t i o n i n t o t h e medium 11

IX (nmol/ml p c v ) + Chlorophthalim

1 53.7 0

0 3.7 0

H e r b i c i d e c o n c e n t r a t i o n i n ( 1 ) was 20 uM and i n (2) 0.08 uM; c u l t i v a t i o n was f o r 2 days; pcv i n d i c a t e s packed c e l l volume ( s e e r e f . 17 f o r d e t a i l s ) .

T a b l e I I . C o n t e n t o f 0£-tocopherol and a s c o r b a t e (mg/100 g d r y w e i g h t ) and t h e r a t i o a s c o r b a t e A t f - t o c o p h e r o l i n d i f f e r e n t p l a n t s p e c i e s d e m o n s t r a t i n g r e l a t i o n t o p e r o x i d a t i v e c e l l damage

Species

a -Tocopherol

Ascorbate

Ratio

C e l l damage *) (%)

Mustard Sicklepod Alfalfa

50 60 10

469 861 143

9.4 14.4 14.3

2 3 12

Lambsquarter Velvetleaf Jimson weed Morning g l o r y

12 50 83 10

58 92 114 2

4.8 1.8 1.4 0.2

25 31 59 68

Buckwheat Pigweed

28 10

537 504

19.2 50.4

41 49

*) I n c r e a s e o f t h e r a t i o d r y w t / f r e s h weight i n % o f u n t r e a t e d c o n t r o l . P l a n t s were sprayed w i t h o x y f l u o r f e n (1 kg/ha) and c u l t i v a t e d i n v e r m i c u l i t e ; a f t e r F i n c k h and K u n e r t ( 2 7 ) .



416

MANAGING

RESISTANCE TO AGROCHEMICALS

»« 1

2000

v

l

g> >s

1

1

Buthionine sulfoximine

1500

k.

•o ,o> "o £

1000

Q.

Peroxidizing Herbicides - ACS Symposium Series (ACS Publications)

Recommend Documents