Using of Some Plant Growth Regulators for Increasing Longan cv. ‘Daw’ Fruit Size

Abstract

The effect of brassinosteroid, gibberellic acid (GA₃) and 1-naphthyl acetic acid (NAA) on longan fruit size were studied in two experiments by spraying the growth regulators on four-year old longan cv. ‘Daw’ trees at 105 days after fruit set. Experiment I, brassinosteriod (BRs) at the concentrations of 0.00 (control), 0.004, 0.01 mg/l were sprayed to the trees. It revealed that BRs 0.01 mg/l gave the biggest fruit size. Experiment II, the treatments consisted of NAA 100 mg/l,  GA₃ 50 mg/l,   BRs 0.01 mg/l, GA₃ 50 mg/l + BRs 0.01 mg/l, GA₃ 50 mg/l + NAA 100 mg/l, NAA 100 mg/l + BRs 0.01 mg/l and water (control). It revealed that all growth regulator treatments gave bigger fruit size, heavier fresh and dry weight and better exocarb color than the control. The BRs and GA₃+NAA tended to have the biggest fruit where as NAA +BRs tended to have the heaviest fresh and dry fruit weight. However, placenta and seed dry weight and exocarb thickness did not significant differences among all treatments.