With the objective to evaluate the effect of concentrations of gibberellic acid in thinning and in the quality improvement in grape clusters cv. Superior Seedless it was carried out an experiment in a commercial orchard in Copa Fruit S.A. farm, in Petrolina-PE. The experiment was arranged in a completely randomized design, with seven treatments (GA3: 0.0, 0.5, 1.0, 2.0, 4.0, 6.0 and 8.0 mg.L-1), four replications and two plants/plot, and the data were interpreted by analysis of variance and regression. The applications of the treatments had been carried out in three phases, the first one before the flower opening and the second and the third with approximately 25% and 80% of flowers opened, respectively, using a volume of 2.000 liters per hectare. The clusters had been harvested with 60 days after pruning and the evaluated characteristics had been: average length of cluster, stem and "shoulders"; density of berries/cm of cluster; mass of fresh matter of the cluster and berries; e diameter and length of berries. The best results for thinning had been gotten with the concentration of 0.5 mg.L-1, which provided a density of 5.39 berries/cm of cluster, from 8.24 berries/cm of cluster gotten from the witness. In relation to the improvement of the quality of clusters and berries, applications of GA3 above of 2.0 mg.L-1, although will show efficiency in the increase of the length of the cluster, had negative effect in the mass of fresh matter of clusters and berries, making the clusters commercially impracticable.
Vitis Vinífera (L.); seedless grapes; crop physiology; mass of fresh matter
