ARGININE DECARBOXYLASE AND PUTRESCINE OXIDASE IN OVARIES OF PISUM-SATIVUM L - CHANGES DURING OVARY SENESCENCE AND EARLY STAGES OF FRUIT-DEVELOPMENT

Enzymatic activities involved in putrescine metabolism in ovaries of P isum sativum L. during ovary senescence and fruit set were investigate d. Accumulation of putrescine was observed during incubation of extrac ts from gibberellic acid-treated unpollinated ovaries (young developin g fruits) but not in extracts from untreated ovaries (senescent ovarie s). Extracts from pea ovaries showed arginine decarboxylase (ADC) acti vity, but ornithine decarboxylase and arginase activity were not detec ted. ADC activity decreased in presenescent ovaries and increased mark edly after induction of fruit set with gibberellic acid. Increases in ADC activity were also observed with application of other plant growth substances (benzyladenine and 2,4-dichlorophenoxyacetic acid), after pollination, and in the slender (la cry(s)) pea mutant. By contrast, p utrescine oxidase activity increased in presenescent ovaries but did n ot increase during early fruit development. All of these results sugge st that ADC and putrescine oxidase are involved in the control of putr escine metabolism. Ovary senescence is characterized by the absence of putrescine biosynthesis enzymes and increased levels of putrescine ox idase and fruit development by an increase in ADC and a constant level of putrescine oxidase.