The 6,6,6-[2H]-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 ยฐC or at 10 ยฐC, and after subsequent ripening for 1 week in darkness at 20 ยฐC . 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'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 ยฐC) . Differences in ABA metabolism were found resulting from storage at the two temperatures, 2 .5 or 10'C . Significantly greater DPA levels were found after 10 ยฐC storage than after 2 .5'C storage (2 weeks) . Levels of ABA ester-conjugates increased with 20'C ripening only after 10 ยฐC storage while free ABA levels decreased after both storage temperature conditions . Levels of DPA conjugates also increased only after 20'C ripening following 10 ยฐC storage . A longer period of storage resulted in decreases of free DPA levels after 10 ยฐC storage but increased DPA levels were found after 2 .5'C storage .
Abbreviations : ABA = abscisic acid, PA = phaseic acid, DPA = dihydrophaseic acid, GC-MS-SIM = gas chromatography-mass spectrometry-selected ion monitoring, HPLC = high pressure liquid chromatography, fw . = fresh weight .