ISHS Acta Horticulturae 343: Physiological Basis of Postharvest Technologies
MODIFICATIONS IN POLYAMINE LEVELS OF CHERIMOYA (ANNONA CHERIMOLA, MILL.) FRUIT DURING THE INITIAL STATE OF STORAGE AT CHILLING TEMPERATURE |
| Authors: | M.I. Escribano, C. Merodio |
| Abstract:
Refrigerated storage is considered to be the most effective method for preserving the quality of fruit, but tropical and subtropical fruits are susceptible to chilling injury by storage at temperatures below the critical value. The response of fruit to chilling injury has frequently been separated into primary and secondary responses (Wang, 1990). However, the actual sequence of events leading to visible symptoms is unknown. Changes in polyamine biosynthesis in plant tissues have been correlated to different kinds of stress (Flores et al., 1985; Basu et al., 1988). Treatment with elevated polyamine levels (spermidine and spermine) as temperature pre-conditioning or low-oxygen storage, have been shown to reduce chilling injury in zucchini squash during storage at 2.5C (Kramer and Wang, 1989; Wang and Ji, 1989). In this study, we analyzed the modifications in polyamine patterns of cherimoya (Annona cherimola, Mill. cv. Fino de Jete) fruit during the first stage of storage at chilling temperature, and its relationship to physiological parameters such as ethylene production and flesh firmness. Free polyamines from mesocarp cherimoya tissue were dansylated and separated by HPLC on a 4.6 mm x 15 cm reverse phase C18 column. The polyamines were eluted with a methanolin water gradient, detected by fluorescence spectrophotometry (excitation 350 nm, emission 495 nm) and quantified using 1,6-hexanediamine as an internal standard. Free spermidine was the predominant polyamine in unripe cherimoya fruit. During ripening at 20C, the level of spermidine decreased, whereas the levels of putrescine increased sharply. These changes in polyamine levels were prior to peak ethylene production. Inhibition of ethylene synthesis and a loss in ripening capacity were observed in fruits stored at 6C. At this temperature, firmness was sustained with a very slight decline until the fifth day, when it fell progressively. In this first stage of storage, the levels of spermidine dropped rapidly to about 67 and 54% of the initial value on the 1st and 3rd days, respectively. While net accumulation of putrescine accompanied ripening of cherimoya fruit at 20C, putrescine and spermine levels decreased to about 50 and 72% of the initial value by the 3rd day of storage at 6C. We have shown that the pattern of polyamine relationships (Sd+Sm/Put) run parallel to flesh firmness during the ripening process. At 6C, the polyamine rate and flesh firmness change only slightly during the 1st days of storage. Our results show a possible relationship between the first stage of storage at 6C and a decline in polyamine levels, suggesting that chilling temperatures may affect either activation of polyamine catabolism or formation of polyamine conjugates. This is in agreement with previous paper indicating that increases | |
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