中文摘要：

以‘津春4号’黄瓜幼苗为试材,采用叶面喷施的方法,研究了外源褪黑素对高温胁迫下黄瓜幼苗叶片抗坏血酸代谢系统的影响.结果表明：高温胁迫后,黄瓜幼苗叶片过氧化氢（H2O2）和丙二醛（MDA）含量明显增加;还原型抗坏血酸（AsA）和还原型谷胱甘肽（GSH）含量持续下降,脱氢抗坏血酸（DHA）和氧化型谷胱甘肽（GSSG）含量逐渐升高,AsA/DHA和GSH/GSSG大幅下降;抗坏血酸过氧化物酶（APx）、单脱氢抗坏血酸还原酶（MDHAR）、脱氢抗坏血酸还原酶（DHAR）和谷胱甘肽还原酶（GR）活性明显升高,并在12 h达到最大.外施褪黑素能有效抑制高温胁迫下黄瓜幼苗叶片H2O2和MDA的积累,提高抗氧化物质AsA和GSH含量及抗坏血酸代谢相关酶APx、MDHAR、DHAR和GR活性,从而增强对H2O2的清除能力,抑制活性氧的产生,维持细胞膜的稳定性,减轻高温对植株造成的伤害,提高黄瓜幼苗抵御高温胁迫的能力.

英文摘要：

Taking cucumber cultivar‘Jinchun 4’as test material,and by the method of foliar spraying,this paper studied the effects of exogenous melatonin （ MT） on the ascorbic acid （ AsA） metabolism system in cucumber seedlings under high temperature stress.Under the stress of high temperature,the leaf hydrogen peroxide （ H2O2） and malondialdehyde （ MDA） contents of the cucumber seedlings increased obviously,ascorbic acid （ AsA） and glutathione （ GSH） contents had a persistent decrease while dehydroascorbate （ DHA） and oxidized-glutathione （ GSSG） contents had a gradual increase,and AsA/DHA and GSH/GSSG decreased greatly.The activities of ascorbate peroxidase （ APx ） ,monodehydroascorbate reductase （ MDHAR ） ,dehydroascorbate reductase （ DHAR） ,and glutathione reductase （ GR） in the seedling leaves under high temperature stress increased markedly,with the maximum after 12 h stress.Foliar spraying MT could effectively restrain the accumulation of H2O2 and MDA in seedling leaves,increase the leaf AsA and GSH contents and the activities of ascorbic acid metabolizing enzymes APx,MDHAR,GR and DHAR,and accordingly,enhance the H2O2-scavenging ability,inhibit the production of active O2,maintain the stability of cell membrane,reduce the damage of high temperature to the plants,and improve the ability of cucumber seedlings against high temperature stress.