UPTAKE AND TRANSLOCATION OF [C-14] MSMA IN COTTON AND MSMA-RESISTANT AND MSMA-SUSCEPTIBLE COCKLEBUR

Common cocklebur (Xanthium strumarium L.) is a competitive weed which interferes with cotton (Gossypium hirsutum L.) production throughout t he southeastern United States. In South Carolina, an organic arsenical -resistant cocklebur biotype has been identified. Absorption and trans location studies were conducted comparing monosodium methanearsonate ( MSMA)-resistant (R) and -susceptible (S)-cocklebur with tolerant cotto n using [C-14]MSMA. Radioactivity was distributed throughout all plant s and average recovery from plants after 1, 3, and 5 days was 98, 70, and 85%, respectively. Greatest concentrations of C-14 activity were l ocated in the treated leaf, with both acropetal and basipetal transloc ation occurring. There were no significant differences in radioactivit y recovered from the three plant types. Cocklebur absorbed more MSMA t han did cotton; most C-14 activity was removed from the treated cotton leaf in the first water rinse. Cotton cuticle appears to play a role in the MSMA tolerance mechanism. No significant C-14 root exudationsor (CO2)-C-14 evolution from intact plants was detected. (C) 1994 Academ ic Press, Inc,