中文摘要：

【目的】研究果实发育期间乙酰水杨酸（ASA）4次喷施处理对厚皮甜瓜果实采收及贮藏期间后熟和软化的影响及作用机理,为采后调控提供参考。【方法】以‘玛瑙’厚皮甜瓜为试材,采用1 mmol·L-1 ASA分别在甜瓜幼果期（花后2周）、膨大期（花后3周）、网纹形成期（花后4周）及采前48 h四个时期连续喷施处理,测定果实采收及冷藏期间（7℃,RH 55%—60%）的呼吸强度和乙烯释放量,硬度、细胞壁组分以及细胞壁降解酶活性的变化。【结果】采前乙酰水杨酸处理可有效降低甜瓜果实采收时的呼吸强度和乙烯释放量,使果实贮藏期间呼吸和乙烯跃变峰的出现时间推迟1周。ASA处理提高了果实采收时的硬度及原果胶、纤维素、半纤维素和富含羟脯氨酸糖蛋白（HRGPs）含量,延缓了原果胶向可溶性果胶的转化,维持了较高的纤维素、半纤维素和HRGPs水平,有效保持了贮藏期间的果实硬度。采前ASA处理显著降低了采收时和贮藏期间甜瓜果实细胞壁降解酶的活性,主要抑制了果实果胶甲酯酶（PME）、多聚半乳糖醛酸酶（PG）、纤维素酶（Cx）和β-葡萄糖苷酶（β-Glu）的活性。相关性分析表明,处理果实的乙烯释放量和呼吸强度与多聚半乳糖醛酸酶（PG）活性呈显著正相关,与β-葡萄糖苷酶（β-Glu）活性呈极显著正相关;处理果实的硬度与果胶甲酯酶（PME）活性、原果胶和半纤维素含量呈极显著正相关,与纤维素酶（Cx）活性和可溶性果胶（WSP）含量呈显著正相关,与乙烯释放量和呼吸强度均呈显著负相关。【结论】采前ASA处理可促进甜瓜果实发育期间细胞壁物质的合成,有效抑制甜瓜果实采收及贮藏期间的呼吸强度和乙烯释放,降低胶甲酯酶（PME）、多聚半乳糖醛酸酶（PG）、纤维素酶（Cx）和β-葡萄糖苷酶（β-Glu）等细胞壁降解酶的活性,阻止细胞壁物质的释放,有效维?

英文摘要：

[ Objective ] The experiment was conducted to study the effects of preharvest acetylsalicylic acid （ASA） sprayed for four times during fruit development on ripening and softening of muskmelon fruit （Cucumis melo cv. Agate） at harvest and during storage, and to explore softing mechanism caused by ASA treatments. [Method] The muskmelon, cultivar ‘Agate＇, was used as material. The plants were sprayed with ASA at lmmol-L1 for four times at young fruit period （2 weeks after flowering）, enlarging period （3 wk after flowering）, netting period （4 wk after flowering） and mature period （preharvest 48 h）. The changes of physiological and biochemical parameters were determined on respiratory rate and ethylene production, firmness, cell wall component and cell wall-degrading enzymes activity of fruit at harvest and during storage （7℃, RH 55%-60%）. [Result] Preharvest spray of ASA significantly decreased respiratory rate and ethylene production of muskmelon fruit at harvest, and delayed climecteric peak and ethylene peak for 1 wk during storage. ASA treatments increased the firmness of fruit, the contents of propectin, cellulose,hemicellulose and hydroxyproline-rich glycoproteins （HRGPs） in fruit at harvest, retarded the conversion of propectin to water soluble pectins （WSP）, maintained a higher level of cellulose, hemicellulose and HRGPs, kept firmness of fruit during storage. Preharvest spray of ASA noticeably decreased the activity of cell wall degrading enzymes in fruit at harvest and during storage, mainly inhibited the activity of pectin methylesterase （PME）, polygalacturonase （PG）, cellulase （Cx） and β-gluosidase （β-Glu）. The correlation analysis indicated that there was a significant positive correlation between ethylene production and PG activity, respiratory rate and PG activity. And a very significant positive correlation between ethylene production and β-Glu activity, respiratory rate and β-Glu activity in treated fruit. There was a highly significant po