Apricots (Prunus armeniaca L. cv Mauricio) harvested at commercial ripening stage were treated with putrescine (1 mM), then mechanically damaged with a 25 N force and stored at 10 °C for 6 d. Putrescine treatment increased fruit firmness and reduced the bruising zones caused by the mechanical damage. Putrescine-treated fruits (both damaged and nondamaged) showed different physiological behavior than controls. Color change, weight loss, ethylene emission, and respiration rate were reduced in putrescine-treated fruits. The most remarkable effect of the mechanical damage was the significant increase in spermidine concentrations found after the compression in control apricots, which could be considered as a physiological marker of mechanical damage.

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 1mM putrescine and 1 mM calcium chloride. Both treatments significantly increased fruit firmness as compared with control fruit in stage 1 lemons. Putrescinetreated fruits showed higher levels of firmness and lower weight loss than calcium-treated or nontreated 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.

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Peaches (Prunus persica L., cv. Babygold 6) harvested at the stage of commercial ripening were pressureinfiltrated with putrescine (1 mM) or GA 3 (100 mg L -1 ) and then stored at 2 °C for 14 d. Both treatments increased fruit firmness, putrescine-treated peaches being significantly firmer than control ones. Treatments were also effective in reducing the susceptibility of the fruit to be damaged by mechanically compression with lower volume and surface of the damage zone. Ethylene emission and the respiration rate were reduced in treated fruits, which reflects a delay of the ripening process. The effects of the mechanical stress could be related to increased spermidine levels, rather than ethylene emission and respiration rate during storage.