EFFECTS OF CHLORSULFURON ON POLYAMINE CONTENT IN MAIZE SEEDLINGS

The effects of chlorsulfuron, a herbicide known to inhibit plant growth by inhibiting cell cycle progression in both G1 and G2 stages, were examined on free polyamine content and on growth in Zea mays seedlings. Chlorsulfuron decreased the spermidine content in active growing tissue, such as root tips, completely unaffecting the spermidine content in the basal part of the root where mitotic activity is lacking. In addition to the effects of specific spermidine inhibitors, methylglyoxal-bis(guanylhydrazone), an inhibitor of S-adenosylmethionine decarboxylase activity, cyclohexylamine, a competitive inhibitor of spermidine synthase activity, and chlorsulfuron were examined on both free and bound polyamines. Chlorsulfuron proved to be able to decrease the free and bound spermidine content more than methylglyoxal-bis(guanylhydrazone) and cyclohexylamine but probably through a different mechanism. In fact the inhibition of free spermidine content induced by methylglyoxal-bis(guanylhydrazone) and cyclohexylamine was reversed by the addition of exogenous spermidine, while no reversal effect was obtained for the inhibition of spermidine content induced by chlorsulfuron. It has been hypothesized that the depletion of spermidine content, induced by chlorsulfuron, could be responsible for the inhibition of cell cycle progression in G1 and G2 stages leading to growth inhibition. © 1990.