SAFENER EFFECTS ON ACETOCHLOR TOXICITY, UPTAKE, METABOLISM AND GLUTATHIONE-S-TRANSFERASE ACTIVITY IN MAIZE

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-dichloroacetyl-1-oxa-4-azaspiro-4,5-decane), BAS-145138 [1-dichloroacetyl-hexahydro-3,3, 8a-trimethyl-pyrrolo(1,2-a)pyrimidin-6(2H)-one], dichlormid (NN,-diallyl-2,2-dichloroacetamide), DKA-24 (N,N2-diallyl-N2dichloroacetylglycineamide) and MG-191 (2-dichloromethyl-2-methyl-1,3-dioxolane). All safeners significantly increased [C-14]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 [C-14]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.