Influence of postharvest treatment with putrescine and calcium on endogenous polyamines, firmness, and abscisic acid in lemon (Citrus lemon L. Burm cv. Verna)

Fruit firmness, free polyamine levels (putrescine, spermidine, and spermine), abscisic acid (ABA), and color index were determined in lemon fruit at two ripening stages (at color break and fully yellow) after vacuum infiltration with 1 mM putrescine and 1 mM calcium chloride. Both treatments significantly increased fruit firmness as compared with control fruit in stage 1 lemons. Putrescine-treated fruits showed higher levels of firmness and lower weight loss than calcium-treated or nontreted fruits during storage. The concentrations of putrescine, spermidine, and spermine were higher in stage 1 than in stage 2 lemons, whereas 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 calcium treatments delayed the color change, which was related to the lowest levels of ABA found.