Absorption, Translocation, and Metabolism of14C-Chlorsulfuron in Canada Thistle (Cirsium arvense)

Absorption of14C-chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino] carbonyl] benzenesulfonanide} by Canada thistle [Cirsium arvense(L.) Scop. # CIRAR] was 39% following foliar treatment and 16% when added to a nutrient solution in which the plants were growing. Translocation from the treated organ was limited regardless of treatment method; 10% of the applied14C moved out of the treated leaf and 10% moved from the roots to other parts of the plant following absorption from the nutrient solution. When applied as a foliar treatment,14C-chlorsulfuron had not been metabolized by Canada thistle 48 h later. However, when14C-chlorsulfuron was added to the nutrient solution and absorbed by the roots, nearly 25% of the14C in the plants was present as a polar product(s), 13% had an Rf value identical to benzenesulfonamide standards, and the remaining 62% was chlorsulfuron. Chlorsulfuron was not transformed similarly in a nutrient solution after 6 days in the absence of plants. Suppression of regrowth was the primary injury symptom observed following chlorsulfuron application. Chlorsulfuron also reduced whole plant weight and root bud number and weight.