| Abstract: | In woody cuttings of the grape vine inflorescences of fertilebuds usually atrophy soon after bud burst. Inflorescences areretained if leaves are removed from the elongating shoot, butremoval of apices and roots does not affect inflorescence growthif leaves are present. With defoliated cuttings, inflorescencegrowth is stimulated by removal of apices but depressed by removalof roots. Applications of indole acetic acid to the petiolestumps of defoliated cuttings did not replace the effect ofleaves and induce atrophy of inflorescences. Inflorescence growthin defoliated cuttings was inhibited by 2,4-dichlorophenoxyaceticacid (2,4-D), but concentrations which depressed inflorescencegrowth produced toxicity symptoms. Applications of 2,3,5-tri-iodobenzoicacid to petioles and leaf laminae were without effect on inflorescencegrowth. Treatment of inflorescences with the cytokinin 6-(benzylamino)-9-(2-tetrahydropyranyl)-9H-purine(SD 8339) promoted inflorescence growth in both the presenceand the absence of leaves. Inhibitory effects of 2,4-D on inflorescencegrowth were partially reversible by application of SD 8339.Response of inflorescences to gibberellic acid required eitherremoval of leaves or addition of SD 8339. |
