PLANT-METABOLISM OF HERBICIDES WITH C-P BONDS - PHOSPHINOTHRICIN

Plants have been reported not to metabolize phosphinothricin. In order to reexamine these literature findings, cell suspension cultures of soybean (Glycine max L.), wheat (Triticum aestivum L.), and maize (Zea mays L.) were incubated with l-[3,4-14C]phosphinothricin. In maize cells which took up up to 50% of the applied radioactivity four different metabolites were detected. They were identified as 4-methylphosphinico-2-oxo-butyric acid, 4-methylphosphinico-2-hydroxybutyric acid, 4-methylphosphinico-butyric acid, and 3-methylphosphinico-propionic acid, respectively. A new HPLC separation method was developed in order to identify these unusually polar metabolites. In soybean and wheat cultures, 10 and 6%, respectively, of the applied radioactivity was taken up. In soybean only one metabolite, 3-methylphosphinico-propionic acid, could be detected whereas in wheat 4-methyl-phosphinico-butyric acid was additionally present. Radioactivity in the culture media could be attributed to unchanged herbicide in all cases. 14CO2-evolution from soybean and maize cultures was very low (<0.1% of the applied radioactivity within 4 days). Incorporation of radioactivity from applied [14C]phosphinothricin into bound residues also reached only small amounts (<0.1%). A metabolism scheme for phosphinothricin is proposed. © 1992.