Involvement of polyamines in gibberellin-induced development of seedless grape berries

The roles of polyamines (PAs) in the development of seedless grape berries induced by gibberellin (GA(3)) was investigated. The development of seedless grape berries was stimulated by the application of putrescine (Put), but not by that of spermidine (Spd) and spermine (Spm), regardless of the presence of GA(3). At harvest, the fresh weight of seedless grape berries treated with 500 ppm Put + 25 ppm GA(3) and 500 ppm Put increased to 111 and 112%, respectively, of the control. Treatment with methylglyoxal-bis (guanyl hydrazone), a potent inhibitor of S-adenosylmethionine decarboxylase that plays a role in Spd and Spm synthesis, did not affect the development of seedless grape berries induced by 100 ppm GA(3). The application of 100 ppm GA(3) significantly increased endogenous free Put levels. Levels of free Spd and Spm were not affected by GA(3). Although the levels of endogenous perchloric acid insoluble bound PAs were higher than those of free PAs, obvious changes in the levels of bound PAs were not observed. These results indicate that free Put is implicated in the development of seedless grape berries induced by GA(3).