CONJUGATED POLYAMINE LEVELS AND PUTRESCINE SYNTHESIS IN CHERIMOYA FRUIT DURING STORAGE AT DIFFERENT TEMPERATURES

In a previous study (J. Plant Physiol. 143, 207-212, 1994) we reported a rise in free putrescine levels in cherimoya fruit (Annona cherimola Mill.) during ripening. In an attempt to explain such an increase, co njugated polyamine levels, arginine decarboxylase (ADC, EC 4.1.1.19) a nd ornithine decarboxylase (ODC, EC 4.1.1.17) activities were determin ed in cherimoya fruit stored at 20, 10, 8 and 6 degrees C. No PCA-inso luble conjugated spermine and PCA-soluble conjugated putrescine titers were detected at any temperature or time interval. PCA-soluble conjug ated spermine titers were observed to decline early on in the low-temp erature storage period. While PCA-insoluble conjugated spermidine cont ent grew steadily in fruit kept at 20 degrees C, it was found to decre ase throughout the storage period in fruit at lower temperatures. Whil e PCA-insoluble conjugated putrescine levels increased in ripe fruit, they were nonetheless substantially lower than the free-form levels. T he rise in putrescine levels in ripening cherimoya fruit was correlate d with greatly enhanced ADC activity. No ODC activity was detected und er any of the experimental conditions. It is suggested that the ripeni ng-related changes in putrescine levels are regulated via ADC-activity -mediated synthesis and that no conjugation is involved in the process .