CHANGES IN THE LEVELS OF ABSCISIC-ACID AND ITS METABOLITES RESULTING FROM CHILLING OF TOMATO FRUITS

The 6,6,6-[H-2]-analogues of abscisic acid (ABA), phaseic (PA) and dihydrophaseic (DPA) acids were used in GC-MS-SIM determination of free and total alkali hydrolyzable ABA, PA and DPA in the pericarp of tomato (Lycopersicon esculentum L. cv. Pik Red) fruit. Determinations were made on breaker-stage fruit stored 1, 2, 3 or 4 weeks at 2.5-degrees-C or at 10-degrees-C, and after subsequent ripening for 1 week in darkness at 20-degrees-C. Two-fold increases in levels of ABA occurred after storage at low temperatures with a slightly but significantly greater increase in ABA level occurring with 2.5-degrees-C storage. These increases in ABA levels were not associated with the appearance of damage symptoms that occurred with storage at the chilling temperature (2.5-degrees-C). Differences in ABA metabolism were found resulting from storage at the two temperatures, 2.5 or 10-degrees-C. Significantly greater DPA levels were found after 10-degrees-C storage than after 2.5-degrees-C storage (2 weeks). Levels of ABA ester-conjugates increased with 20-degrees-C ripening only after 10-degrees-C storage while free ABA levels decreased after both storage temperature conditions. Levels of DPA conjugates also increased only after 20-degrees-C ripening following 10-degrees-C storage. A longer period of storage resulted in decreases of free DPA levels after 10-degrees-C storage but increased DPA levels were found after 2.5-degrees-C storage.