EffectsofexogenousGA₃onleafsenescenceandendogenoushormonescontentoftheleavesinmuskmelonfruitingnodes

In this study, the effects of exogenous GA₃ on leaf senescence and endogenous hormones content of the leaves in muskmelon fruiting nodes were investigated. Muskmelon cultivar ‘Yingchun(F₁)’ was used as the model and it was treated with exogenous GA₃ solutions of different concentrations. The results of this study could provide a solution for delaying the premature senescence phenomenon and improving the yield and quality of fruit. The physiological indexes, including the concentration of chlorophyll and soluble protein, antioxidant enzyme activity, active oxygen, endogenous hormone content and fruit quality were determined in this work. Compared with the control, the concentrations of chlorophyll and soluble protein of the leaves in fruiting nodes were increased, and the activities of antioxidant enzymes were enhanced. While the rate of superoxide anion production was reduced, and the growth of MDA content was depressed at different levels by treating with exogenous GA₃ solutions of different concentrations (50, 100, 150 mg/L). Meanwhile, the growth of abscisic acid was also inhibited, the concentrations of auxin, gibberellin and zeaxanin were increased, and the fruit yield and quality were improved. Treating with GA₃ of suitable concentration on leaf surfaces has a positive effect on the regulation of antioxidant enzyme system and endogenous hormone content of the leaves in muskmelon fruiting nodes. Therefore, it can be used to postpone the senescence of leaves in the fruiting nodes and improve the qualities of the fruits. Under the conditions used in this study, 100 mg/L exogenous GA₃ solution was the most effective for delaying premature senescence. And it could decrease the content of abscisic acid in fruit-setting leaves by 19.22% on average, while the contents of zeatin nucleoside, auxin and endogenous gibberellin was increased by 14.60%, 23.50% and 56.13% on average, respectively.