INHIBITION OF POLYAMINE BIOSYNTHESIS BY L-CANAVANINE AND ITS EFFECT ON MERISTEMATIC ACTIVITY, GROWTH, AND DEVELOPMENT OF ZEA MAYS ROOTS

ABSTRACT The effects of L-canavanine, a structural analogue of L-arginine and a competitive inhibitor of arginine decarboxylase, were studied in corn (Zea mays L.) on primary root elongation and lateral root differentiation, meristematic activity, and on polyamine content and biosynthesis. Incubation of seedlings in 10−3 M L-canavanine for 3 h inhibited both elongation of the primary root and differentiation of lateral root primordia. A marked decrease in cell division and DNA synthesis, along with an inhibition of the activation of the primary root quiescent center, was clearly evident in L-canavanine-treated roots. Putrescine content in subapical segments of the primary root decreased significantly during the first 24 h, while spermidine content increased at 48–72 h, coinciding with lateral root emergence and elongation. A 3 h incubation with 103 M L-canavanine completely inhibited the increase in spermidine content, thus modifying the ratio of putrescine to spermidine tissue concentrations. The activit...