Polyamine response to external mechanical bruising in two mandarin cultivars

Abstract

The polyamines putrescine, spermidine, and spermine (free form) were measured during 48 hours at 20°C after mechanical damage of 'Fortune' and 'Clementine' mandarins (Citrus reticulata Blanco.) with forces of 0, 10, 20, and 30 N. In control fruits (without damage), the three polyamine levels were higher in 'Fortune' than in 'Clementine', and putrescine and spermine levels tended to diminish during the experiment, while spermidine levels increased slightly in 'Fortune' and showed a prominent peak in 'Clementine' 6 hours after storage. In general, polyamine levels increased in the peel following bruising. The magnitude of this effect differed for both cultivars and applied forces. Putrescine levels were positively correlated with the applied force in 'Fortune', while in 'Clementine' only the 20 N force was effective. Spermidine levels also increased in 'Fortune' following injury, but there was no difference in effects among the three forces used. Only the 10 N force increased spermidine levels significantly in 'Clementine'. Spermine levels were slightly higher than control levels after 48 hours, but not higher than initial levels.