Acetolactate synthase activity and foliar absorption in the presence of chlorsulfuron in biotypes of Cirsium arvense (L.) Scop.

The mechanism of acetolactate synthase (ALS) resistance to the inhibitory action of sulfonylurea is due to the selection of R1 and R2 biotypes of C. arvense with modified form of the ALS enzyme. They are less susceptible to the inhibition of sulfonylurea, but still functional. There was no significant difference between the susceptible and sulfonylurea-resistant biotypes in absorption and translocation of chlorsulfuron