Metabolism of diclofop‐methyl in cell cultures of Avena sativa and Avena fatua

Abstract

The metabolism of the herbicide, diclofop‐methyl (methyl‐2‐[4‐(2′, 4′‐dichlorophenoxy) phenoxy]propanoate), in cell suspension cultures of Avena sativa L. (cv. Garry) and in callus of Avena fatua L. (transferred to liquid) was determined as a function of time (8 h to about 3 weeks) and was compared to previous metabolism data from intact plants. A. fatua metabolized 14C‐labeled diclofop‐methyl more rapidly than A. sativa, but the metabolites formed were similar if not identical. Within 2 days, approximately 50% of the total 14C recovered was in A. fatua cells whereas less than 15% was in A. sativa cells. In older cultures of A. fatua, the amounts of 14C in the cells and in the medium were about 45% each; 10 to 12% was in the non‐extractable cell residue. The 14C recovered from A. sativa cells increased to a maximum of about 35% at 7 days and then slowly decreased to about 18% by 21 days, whereas the 14C in the medium of A. sativa decreased to about 60% at 7 days and then increased to over 75% by 21 days. The nonextractable 14C residue was 5% or less even after 21 days. Major metabolites in methanolic extracts of cells of both A. sativa and A. fatua were diclofop (2‐[4‐(2′, 4′‐dichlorophenoxy)phenoxy] propanoate), diclofop hydroxylated at an undetermined position on the 2,4‐dichlorophenyl ring (ring OH‐diclofop), and conjugates of diclofop and ring‐OH diclofop.