Metabolism of chlortoluron in tolerant species: possible role of cytochrome P‐450 mono‐oxygenases

Abstract

SummaryPathways of chlortoluron metabolism were compared in excised leaves of four tolerant species, namely wheat (Triticum aestivum var Clement), Bromus sterilis, Galium aparine and Veronica persica. The herbicide was principally detoxified by hydroxylation of the ring methyl in wheat and by N‐dealkylation in Veronica persica. Both pathways were involved in Bromus sterilis and Galium aparine. Kinetic study of the degradation showed that capacity to form non‐toxic conjugates could, at least partially, explain the tolerance of these species to chlortoluron. In plants treated with 1‐aminobenzotriazole, a cytochrome P‐450 enzyme inactivator, N‐dealkylation of chlortoluron was little or not affected, but ring methyl hydroxylation was strongly inhibited. This suggests that at least two distinct enzymatic systems could participate in this metabolism. Moreover, cytochrome P‐450 enzymes could be involved in the ring methyl hydroxylating reaction.