THE EFFECT OF MONOOXYGENASE AND GLUTATHIONE-S-TRANSFERASE INHIBITORS ON THE METABOLISM OF DICLOFOP-METHYL AND FENOXAPROP-ETHYL IN BARLEY AND WHEAT

Etiolated shoot segments of wheat (Triticum aestivum L. cv. Fredrick) and barley (Hordeum vulgare L. cv. Legér) were incubated in buffer amended with the herbicides fenoxaprop-ethyl (FE) or diclofop-methyl (DM) and the metabolic inhibitors tetcyclacis (Tc) or tridiphane (Tf). In the absence of the metabolic inhibitors, FE was more rapidly metabolized to polar compounds in wheat than in barley, while the rate of metabolism of DM was similar in the two grass species. Tc inhibited the metabolism of DM and FE in both wheat (98%) and barley (53%), suggesting a possible role of a cytochrome P450-dependent monooxygenase in the detoxification of the two herbicides. The inhibiting effect of Tc was stronger for DM than for FE. Tf did not affect the metabolism of FE in either barley or wheat. The metabolism of DM was reduced by Tf (27%) in wheat. However, this inhibition was significantly less than that of Tc. The herbicide safener, fenchlorazole-ethyl (FCE), enhanced the metabolism of FE in both barley and wheat without affecting the pattern of metabolism. The effect of FCE on FE metabolism was annulled by Tc and Tf in both plant species. © 1993 Academic Press. All rights reserved.