INFLUENCE OF POSTHARVEST TREATMENT WITH PUTRESCINE AND CALCIUM ON ENDOGENOUS POLYAMINES, FIRMNESS, AND ABSCISIC-ACID IN LEMON (CITRUS-LEMONL. BURM CV VERNA)

Fruit firmness, free polyamine levels (putrescine, spermidine, and spe rmine), abscisic acid (ABA), and color index were determined in lemon fruit at two ripening stages (at color break and fully yellow) after v acuum infiltration with 1 mM putrescine and 1 mM calcium chloride. Bot h treatments significantly increased fruit firmness as compared with c ontrol fruit in stage 1 lemons. Putrescine-treated fruits showed highe r levels of firmness and lower weight loss than calcium-treated or non treted fruits during storage. The concentrations of putrescine, spermi dine, and spermine were higher in stage 1 than in stage 2 lemons, wher eas the opposite was found for ABA. The treatment with putrescine was the most effective to maintain higher levels of endogenous putrescine and spermidine, but only for stage 2 fruit. Both putrescine and calciu m treatments delayed the color change, which was related to the lowest levels of ABA found.