Atrazine metabolism in resistant and susceptible biotypes of Chenopodium album L., Chenopodium strictum Roth., and Amaranthus powellii S. Wats.

Summary The metabolism of atrazine was studied in resistant and susceptible biotypes of Chenopodium album L., Chenopodium strictum Roth., and Amaranthus powellii S. Wats. Both biotypes metabolized atrazine by N ‐dealkylation, hydroxy lation at the 2‐position and conjugation. In addition, binding of mono‐ N ‐dealkylated atrazine with plant constituents to form nonextractable (bound) residues was also observed. Although parent atrazine levels were similar in the shoots and roots of both biotypes of the three weed species, the resistant biotype in each case contained a higher level of polar conjugates and bound residues in the plant tissues. In contrast, presence of a phytotoxic metabolite, namely 2‐chloro‐4‐amino‐6‐isopropylamino‐ s ‐triazine, was only observed in the susceptible biotype of the three weed species.