TRANSLOCATION, AND METABOLISM OF C-14 MSMA IN ORGANIC ARSENICAL-RESISTANT AND ARSENICAL-SUSCEPTIBLE MISSISSIPPI BIOTYPES OF COMMON COCKLEBUR (XANTHIUM-STRUMARIUM L)

The uptake, translocation, and metabolism of C-14-MSMA in organic arse nical-resistant (R) and -susceptible (S) Mississippi biotypes of commo n cocklebur were investigated, The two biotypes did not differ signifi cantly with respect to either uptake, total translocation, or transloc ation pattern of C-14-MSMA plus its radiolabeled metabolites regardles s of whether plants were pre-treated with 1.12 kg al ha(-1) of unlabel ed MSMA or treated only with radiolabeled material, Absorption of C-14 -MSMA was greater in unlabeled MSMA-pretreated plants than untreated p lants, whereas the percent of total absorbed C-14-MSMA that was transl ocated out of the C-14-MSMA-treated leaf was almost the same in MSMA-p retreated and untreated plants, Qualitative detection of C-14-MSMA dis tribution by autoradiographs confirmed quantitative results obtained w ith radioassays, Herbicide metabolism in the C-14-treated leaf showed that MSMA was not readily broken down in both biotypes and the extract able C-14 was the same, Uptake, translocation, and metabolic degradati on were not involved in the mechanism of resistance of the resistant-M ississippi biotype common cocklebur to MSMA.