ALBERT

Notes: The ability of the herbicide safeners, BAS-145138 (1-dichloroacetyl-hexahydro-3,3,8a-trimethyl-pyrrolo(1,2a)pyrimidin-6(2H)-one), dichlormid (N,N-diallyl-2,2-dichloroacetamide), flurazole (phenylmethyl ester), and MG-191 (2-dichloromelhyl-2-methyl-1,3-dioxolane) for preventing metazachlor injury to maize (Zea mays L.) and sorghum (Sorghum bicolor L.) seedlings were compared with their effects on 14C-metazachlor metabolism to a glutathione (GSH) conjugate, effects on non-protein thiol contents (mainly GSH) and effects on Glutathione S-transferase (GST) activity in these two species.Sorghum shoot growth was reduced by 41% and maize shoot growth was reduced by 54%, by metazachlor concentrations in vermiculite nutrient culture of 0·6 μM and 7·5μM, respectively. In this system, all four compounds had significant activity as safeners for metazachlor in both sorghum and maize seedlings. BAS-145138 and flurazole were the most effective safeners in maize and sorghum, respectively. In the absence of safeners, the rate of non-enzymatic conjugation of metazachlor and GSH was much greater than the enzymatic rate. However, the rate of enzymatic conjugation of metazachlor with GSH was increased by safener treatment in both maize and sorghum. Safener effectiveness was highly correlated with increases in 14C-metazachlor uptake and metabolism in both species. Safener effectiveness was more highly correlated with safener effects on GST activity in maize or sorghum when 14C-metazachlor was used as the substrate than when the non-specific CDNB (1-chloro-2,4-dinitrobenzene) was used as the substrate. Safener effectiveness was also strongly correlated with safener effects on GSH levels in sorghum, but not in maize, possibly because of the greater importance of non-enzymatic conjugation of metazachlor with GSH in sorghum as compared to maize.

Notes: The effect of five herbicide safeners on preventing maize (Zea mays L.) injury by acetochlor [N-(2-ethyl-6-methyl-phenyl)-N-(ethoxymethyl)-chloroacetamide], their influence on herbicide uptake and metabolism to a glutathione (GSH) conjugate as well as on GSH content and glutathione S-transferase activity (GST) in untreated and herbicide with/without safener-pre-treated 4-day-old seedlings were determined. The safeners studied were: AD-67 (N-di-chloroacetyl-1-oxa-4-azaspiro-4-5-decane), BAS-145138 [1-dichloroacetyl-hexahydro-3,3,8a-trimethyl-pyrrolo(l,2-a)pyrimidin-6(2H)-one], dichlormid (N, A,-diallyl-2,2-dichlo-roacetamide), DKA-24 (N, N2-diallyl-N2dichloroacetylglycineamide) and MG-191 (2-dichloromethyl-2-methyl-1,3-dioxolane). All safeners significantly increased [14C]acetochlor uptake and metabolism rate, maize GSH content and GST activity. Seedlings receiving BAS-145138 pre-treatment metabolized almost 70% of the absorbed [14C]acetochlor within 10 min.Safener-enhanced GST activity was always found to be higher when [14C]acetochlor was used as the substrate compared with CDNB (1-chloro-2,4-dinitrobenzene). Although DKA-24 had a significantly lower influence on both herbicide metabolism and GST activity, it was nearly as effective a safener as BAS-145138, while the others provided no or poor protection to maize from acetochlor injury when they were not incorporated in the soil. Effets d'antidotes sur la toxicité, la pénétration et le métabolisme de I'acétochlore chez le mats etsur l'activité glutathion S-transférase Cinq antidotes d'herbicides diminuaient la toxicité de 1'acétochlore [N-(2-éthyl-6-méthyl-phényl)-N-(éthoxyméthyl)-chloroacétamide] à I'égard du maïs (Zea mays L.). Lew effet sur l'absorption de l'herbicide et sur son métabolisme en un conjugué avec le glutathion (GSH), de même que leur effet sur la teneur en GSH et 1'activité glutathion 5-transférase (GST) ont étéétudiés sur des maïs âgés de 4 jours. Les antidotes étaient: l'AD-67 (N-dichloroacétyl-1-oxa-4-azaspiro-4,5-décane), le BAS-145138 [1 -dichloroacétyl-hexahydro-3,3,8a-triméthyl-pyrrolo(l,2-a) pyrimidine-6(2H)-one], le di-chlormide (N, N-diallyl-2,2-dichloracétamide), le DKA-24 (N, N2-diallyl-N2-dichloracétylgly-cineamide] et le MG-191 (2-dichlorométhyl-2-méthyl-l,3-dioxolane). Tous les antidotes augmentaient de manière significative 1'absorption et le métabolisme de I'acétochlore 14C, ainsi que la teneur du maïs en GSH et son activité GST. Les jeunes plantes prétraitées avec le BAS-145138 métabolisaient en 10 min près de 70% de I'acétochlore 14C absorbé. L'activité GST stimulée par 1'antidote était toujours plus élevée avec I'acétochlore 14C comme substrat qu'avec le CDNB (1-chloro-2,4-dinitrobenzène).Le DKA-24 avait un effet significativement plus faible que le BAS-145138 sur le métabolisme de l'herbicide et sur l'activité GSH, mais son action antidote était presque aussi importante. Les autres produits n'apportaient au maïs qu'une protection faible ou nulle contre l'acétochlore quand ils n'étaient pas incorporés au sol. Wirkung von Safenern auf die Phytotoxizität, Aufnahme und Metabolismus von Acetochlor und die Glutathion-S-Transferase-Aktivität in Mais Die Wirkung von 5 Safenern (AD-67, BAS-145138, Dichlormid, DKA-24 und MG-191; chemische Bezeichnungen s.o.) auf die Phytotoxizität von Acetochlor für Mais (Zea mays L.) und ihr Einfluß auf die Aufnahme des Herbizids und Metabolismus zu einem Glutathion-(GSH-) Konjugat und auf die Glutathion-S-Transferase-(GST-)Aktivität wurde an 4 Tage alten Keimpflanzen untersucht. Durch die Vorbehandlung mit den Safenern wurden die [14C]-Acetochlor-Aufnahme- und -Metabolierungsrate, der GSH-Gehalt und die GST-Ak-tivität signifikant erhöht. Mit BAS-145138 vorbehandelte Keimpflanzen metabolisierten fast 70% des absorbierten [14C]-Acetochlor innerhalb von 10 min. Die durch die Safener erhöhte GST-Aktivität bei [14C]-Acetochlor als Substrat war im Vergleich zu Chlordinitroben-zen immer höher. Obwohl DKA-24 einen signifikant geringeren Einfluß sowohl auf den Herbizidmetabolismus als auch auf die GST-Aktivität hatte, war es fast so wirkungsvoll wie BAS-145138, während die anderen ohne Einarbeitung in den Boden für den Mais keinen oder geringen Schutz gegen Schäden durch Acetochlor boten.