ABSORPTION, TRANSLOCATION, AND METABOLISM OF CLOMAZONE, METRIBUZIN AND LINURON IN SOYBEAN (GLYCINE-MAX) AND COMMON COCKLEBUR (XANTHIUM-STRUMARIUM)

Research was conducted in soybean and common cocklebur to determine if the synergistic interactions of clomazone plus metribuzin and clomazone plus linuron were due to the effect of one herbicide on root uptake, partitioning, or metabolism of the other. Treatments consisted of C-14-clomazone alone and combined with metribuzin or linuron, C-14-metribuzin alone and combined with clomazone, and C-14-linuron alone and combined with clomazone. Root uptake and partitioning of clomazone applied alone in soybean differed compared to clomazone plus metribuzin. Root uptake and partitioning of metribuzin or linuron did not differ when applied alone or combined with clomazone. Binding of clomazone or its metabolites in an unextractable form may be a method of deactivating clomazone by soybean, but not by common cocklebur. Levels of parent clomazone were higher in common cocklebur roots when clomazone was combined with metribuzin and linuron compared to clomazone alone. Levels of parent metribuzin were higher in soybean roots, and in common cocklebur roots and shoots when clomazone was combined with metribuzin compared to metribuzin alone. Levels of parent linuron were greater in soybean shoots when linuron was applied with clomazone compared to linuron alone. These results indicate that the metabolism of metribuzin and linuron is altered in both species when clomazone is applied, leading to increased phytotoxicity.