Using urea phosphate to enhance the effect of gibberellin A3 on grape size

Abstract

Gibberellic acid (GA 3 ) is widely used to enlarge the berries of seedless grapes (Vitis vinifera L) . In cv . `Sultana' (Thompson Seedless) the addition of 1000 mg/L urea phosphate (UP) to GA 3 solutions after fruit set reduced the pH of the solutions to a stable pH 2 .9 and enhanced the effect of GA3 on berry size and delayed maturation . Addition of citrate buffer, pH 2.9, to GA3 sprays did not affect berry size or maturation . The possibility of improved GA penetration due to the low pH is considered . The nutritional effect of UP and direct enhanced penetration by the urea ion are also discussed.