Effects of Some Growth Regulators on Polyamine Biosynthetic Enzymes in Etiolated Pea Seedlings

This study was designed to examine possible links between polyaminebiosynthesis and effects of growth regulatory compounds. Anauxin (IAA), a cytokinin benzyladenine; benzylaminopurine (BAP)],an ethylene source (ethephon) and abscisic acid (ABA) were individuallyapplied to terminal buds of excised etiolated or red light (R)-exposedpea epicotyls. Effects were noted on bud fresh weight and onthe two main enzymes of putrescine biosynthesis, arginine decarboxylase(ADC; EC 4.1.1.19 EC] ) and ornithine decarboxylase (ODC; EC 4.1.1.17 EC] ).As previously reported Dai and Galston (1981) Plant Physiol.67: 266], both bud growth and ADC activity are increased byR light. In such buds, ADC is raised further by 1–10 µMBAP or ABA and inhibited by 1–10 µM IAA or ethylene(50 mg/liter or more of ethephon). In all cases, effects ofR-irradiation plus 1 mM growth regulators on ODC activity wasthe inverse of their effects on ADC, indicating independentcontrol of these pathways. These results do not support theview that putrescine biosynthetic activity is correlated withgrowth in etiolated pea seedlings. ¹Supported by a grant from NSF to A.W.G. ²Supported by a grant from the Turkish Government. Permanentaddress: Department of General Botany, University of Istanbul,S?leymaniye, Istanbul, Turkey. ³On sabbatical leave from the Department of Horticulture, HebrewUniversity of Jerusalem, Rehovot, Israel. (Received September 22, 1983; Accepted February 28, 1984)