Uptake, Translocation, and Metabolism of14C-MSMA in Organic Arsenical-Resistant and -Susceptible Mississippi Biotypes of Common Cocklebur (Xanthium strumariumL.)

Abstract

The uptake, translocation, and metabolism of14C-MSMA in organic arsenical-resistant (R) and -susceptible (S) Mississippi biotypes of common cocklebur were investigated. The two biotypes did not differ significantly with respect to either uptake, total translocation, or translocation pattern of14C-MSMA plus its radiolabeled metabolites regardless of whether plants were pre-treated with 1.12 kg ai ha−1of unlabeled MSMA or treated only with radiolabeled material. Absorption of14C-MSMA was greater in unlabeled MSMA-pretreated plants than untreated plants, whereas the percent of total absorbed14C-MSMA that was translocated out of the14C-MSMA-treated leaf was almost the same in MSMA-pretreated and untreated plants. Qualitative detection of14C-MSMA distribution by autoradiographs confirmed quantitative results obtained with radioassays. Herbicide metabolism in the14C-treated leaf showed that MSMA was not readily broken down in both biotypes and the extractable14C was the same. Uptake, translocation, and metabolic degradation were not involved in the mechanism of resistance of the resistant-Mississippi biotype common cocklebur to MSMA.