Herbicide Resistant Weeds

Uptake, translocation, and metabolism of 14C-MSMA in organic arsenical-resistant and -susceptible Mississippi biotypes of common cocklebur (Xanthium strumarium L.).

Nimbal, C. I., G. D. Wills, S. O. Duke, and D. R. Shaw. 1995. Uptake, translocation, and metabolism of 14C-MSMA in organic arsenical-resistant and -susceptible Mississippi biotypes of common cocklebur (Xanthium strumarium L.). Weed Science. 43: 549-554.

The uptake, translocation and metabolism of 14C-MSMA in organic arsenical-resistant and -susceptible Mississippi biotypes of common cocklebur were investigated. The two biotypes did not differ significantly with respect to either uptake, total translocation or translocation pattern of 14C-MSMA plus its radiolabelled metabolites regardless of whether plants were pretreated with 1.12 kg ai ha-1 of unlabelled MSMA or treated only with radiolabelled material. Absorption of 14C-MSMA was greater in unlabelled MSMA-pretreated plants than untreated plants, whereas the percentage of total absorbed 14C-MSMA that was translocated out of the 14C-MSMA-treated leaf was almost the same in MSMA-pretreated and untreated plants. Qualitative detection of 14C-MSMA distribution by autoradiographs confirmed quantitative results obtained with radioassays. Herbicide metabolism in the 14C-treated leaf showed that MSMA was not readily broken down in both biotypes and the extractable 14C 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.