ARGINASE, ARGININE DECARBOXYLASE, ORNITHINE DECARBOXYLASE AND POLYAMINES IN TOMATO OVARIES - CHANGES IN UNPOLLINATED OVARIES AND PARTHENOCARPIC FRUITS INDUCED BY AUXIN OR GIBBERELLIN

Arginase (EC 3.5.3.1) activity has been found in the ovaries and young fruits of tomato (Lycopersicon esculentum Mill. cv Rutgers). Changes in arginase, arginine decarboxylase (EC 4.1.1.19), and ornithine decar boxylase activity (EC 4.1.1.17) and levels of free and conjugated putr escine, spermidine, and spermine were determined in unpollinated ovari es and in parthenocarpic fruits during the early stages of development induced by 2,4-dichlorophenoxyacetic acid (2,4-D) or gibberellic acid (GA(3)). Levels of arginase, free spermine, and conjugates of the thr ee polyamines were constant in unpollinated ovaries and characteristic of a presenescent step. A marked decrease in arginase activity, free spermine, and polyamine conjugates was associated with the initiation of fruit growth due to cell division, and when cell expansion was init iated, the absence of arginase indicated a redirection of nitrogen met abolism to the synthesis of arginine. A transient increase in arginine decarboxylase and ornithine decarboxylase was also observed in 2,4-D- induced fruits. In general, 2,4-D treatments produced faster changes t han GA(3), and without treatment, unpollinated ovaries developed only slightly and senescence was hardly visible. Sensitivity to 2,4-D and G A(3) treatment remained for at least 2 weeks postanthesis.