Metabolism of Chloro s-Triazine Herbicides by Panicum and Setaria

Six Setaria species and varieties and three Panicum species were allowed to absorb 14C-labeled 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine), 2-chloro-4,6-bis(isopropylamino)-s-triazine (propazine), and/or 2-chloro-4,6-bis (ethylamino)-s-triazine (simazine). The grasses metabolized the herbicides to water-soluble derivatives. Peptide conjugates were the only major metabolites formed by each species or variety; however, hydroxyderivatives of the herbicides were detected. The order of ability of the Setaria and Panicum species and varieties to metabolize atrazine and/or propazine was similar to the order of their tolerance to atrazine and/or propazine. Several Setaria and Panicum species and varieties formed peptide conjugates of atrazine and/or propazine to which they are resistant, more rapidly than they formed peptide conjugates of simazine, to which they are susceptible.