RIPENING AFFECTS HIGH-TEMPERATURE-INDUCED POLYAMINES AND THEIR CHANGES DURING COLD-STORAGE OF HYBRID FORTUNE MANDARINS

Polyamine levels were measured in the flavedo of three ripening stages of Fortune mandarins exposed to high-temperature conditioning before storage at a chilling (2 degrees C) and a nonchilling temperature (12 degrees C). Increasing periods of conditioning at 37 degrees C delayed the development of chilling injury (CI) and produced an increase in t he content of the polyamines in the following proportion spermine > sp ermidine > putrescine. Storage at 2 degrees C of conditioned fruits re duced the polyamine titer to levels similar to those of nonconditioned fruits. Changes in polyamines during storage of conditioned and nonco nditioned fruits were dependent on the ripening stage of the fruit. In general, the levels of polyamines in nonconditioned fruits stored at 2 and 12 degrees C were similar. No change in spermine was induced in the most mature fruits at 2 degrees C or in response to high-temperatu re conditioning despite conditioning-reduced CI. With this exception, the data indicate that conditioning fruits at 37 degrees C elevated th e content of polyamines and reduced CI in Fortune mandarins.