外源赤霉素对厚皮甜瓜坐果节位叶片早衰与内源激素含量的影响

采用全株叶片喷施外源赤霉素 (GA₃) 的方法，以黄瓜品种‘迎春’为试材，通过对黄瓜坐果节位叶片中的叶绿素、可溶性蛋白质、抗氧化酶活性、活性氧及内源激素含量等各项生理指标及果实品质指标进行测定，探究GA₃对厚皮甜瓜坐果节位叶片早衰及内源激素含量变化的调控作用，为延缓厚皮甜瓜坐果节位叶片早衰并提高其果实产量和品质提供理论依据。结果显示:与对照相比，叶面喷施50、100和150 mg/L的外源GA₃水溶液可不同程度地增加坐果节位叶片中的叶绿素和可溶性蛋白含量，提高其抗氧化酶活性，降低超氧阴离子产生速率，减缓丙二醛含量的增长，同时抑制脱落酸的增长，提升生长素、赤霉素和玉米素核苷水平，最终显著改善果实产量和品质。通过叶面喷施适宜浓度外源GA₃，对厚皮甜瓜坐果节位叶片抗氧化酶系统和内源激素含量的调控产生积极影响，从而延缓叶片早衰并提高果实产量和品质。在本试验条件下，喷施100 mg/L的外源GA₃水溶液延缓早衰效果最佳，且在各个时期能够使坐果叶片内脱落酸含量分别平均降低19.22%，玉米素核苷、生长素和内源赤霉素含量分别平均升高14.60%、23.50%和56.13%。

Effects of exogenous GA3 on leaf senescence and endogenous hormones content of the leaves in muskmelon fruiting nodes

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.