Changes of endogenous levels of ABA, IAA and GA-like substances in fruitlets of parthenocarpic persimmon.

摘要

The reproductive organ of parthenocarpic persimmon cv. Hiratanenashi was sampled from -5 to 122 days after flowering (DAF). Fruitlet abscission occurred mainly from 13 to 62 DAF and peaked at 41 DAF. A relatively rapid increase of fresh weight of fruitlets occurred until 41 DAF; thereafter, the growth rate was moderate. The weight of the calyx increased until 13 DAF. The ABA concentration in fruitlets was higher from flowering to 28 DAF than during the remaining period. The calyx at 13 DAF had thegreatest ABA concentration of all parts analysed. IAA in the ovary/fruitlet increased about 18 times in content and 5 times in concentration from -5 to 0 DAF, and decreased to less than half in content by 13 DAF. The concentration of gibberellin(GA)-likesubstances in fruitlets at flowering was also high, and increased at 41 and 122 DAF. At 5 days before flowering, the calyx had a higher concentration and content of the 3 growth regulators than the ovary. These results suggest that the increases of IAAand GA-like substances in the fruitlet of parthenocarpic persimmons during flowering may result in continued growth, but the interaction between increased ABA and decreased IAA and GA-like substances in the fruitlet before fruitlet-drop may induce its abscission.