ASPECTS OF ETHYLENE BIOSYNTHETIC PATHWAY IN TOMATO FRUITS DURING THE RIPENING PROCESS

Green fruits of normal ripening type of tomatoes ( Lycopersicon esculentum Mill) were picked 13-39 days after anthesis and stored at 20°C. Although more days were required for the ripening of the fruits if the stage of picking was earlier, all fruits became red and soft during storage. This result shows that considerably immature fruits have the ability of ripening. Green tomato fruits at three stages (18. 29 and 38 days after anthesis) were treated with ethylene for one day. The activity of ethylene forming enzyme (EFE) and the conversion of applied 1-aminocyclopropane-1-carboxylic acid (ACC) to N-malonyl-ACC (MACC) in the three stages of tomato fruits were accelerated by exogenous ethylene, though endogenous ethylene production was hardly observed. When the green tomato fruits (31-34 days after anthesis) were treated with ethylene for one day and then transferred to air. the activity of EFE and the conversion of applied ACC to MACC were depressed. The activity of ACC synthase was not accelerated by ethylene treatment of only one day, but was accelerated by a longer term treatment, followed by increased ethylene production and the onset of ripening.