Cucumber(Cucumis sativus.L)was used as a test material and we used polyethylene glycol to sim-ulate drought stress to cucumber.The effect of H2O2and ABA on adventitious root development of cucumber(Cuc-umis sativus.L)under drought stress and their interrelationship were studied.The results indicated that 0.3％PEG could simulate moderate drought stress.Exogenous H2O2and ABA had significant positive effect on adventitious root development of cucumber explants under drought stress and the effect was dose-dependent with a maximal biological response at 800 μmol·L-1H2O2and 0.5 μmol·L-1ABA treatment.The root number developed in H2O2+ABA treatment was 19.3％and 31.3％higher than that in H2O2or ABA single treatment,respectively.Compared with ABA single treatment,the root numbers in ABA+H2O2scavenger(CAT)or ABA+H2O2inhibitor(DPI)treat-ment decreased by 15.2％and 30.9％,respectively under drought stress.The root length decreased by 24.1％and 26％,respectively.The results showed that PEG+ABA treatment has decreased stomatal aperture,density and rel-ative electric conductivity by 24.2％,15.4％and 14.2％compared to the PEG treatment; while it has increased the relative water content by 25％.Moreover,PEG+ABA treatment has increased the content of osmotic adjustment substances(praline,water soluble carbohydrate and soluble protein)and the activity of the peroxidase,polyphenol oxidase and indoleacetate oxidase,while has decreased the content of malondialdehyde.However,CAT treatment significantly reversed the promoting function of ABA in adventitious root formation under drought stress.Therefore,endogenous H2O2might be regulating water balance,cell membrane stability,osmotic adjustment substances and rel-ative enzyme activity,involving in the signaling pathway of ABA-induced adventitious rooting under drought stress.%以黄瓜(Cucumis sativus.L)为试材,采用聚乙二醇(PEG)模拟干旱胁迫,研究过氧化氢(H2O2)与脱落酸(ABA)在干旱胁迫下对黄瓜不定根发生的作用及其相互关系.结果表明:0.3％PEG产生了中度干旱胁迫.干旱条件下外源H2O2和ABA可以显著促进黄瓜外植体不定根的发生,且呈明显的剂量效应,800 μmol·L-1H2O2和0.5 μmol·L-1ABA促进效果最显著.干旱胁迫下H2O2和ABA共同处理的根数较H2O2或ABA单独处理分别高19.3％和31.3％.干旱胁迫下ABA与内源H2O2清除剂过氧化氢酶(CAT)或内源H2O2合成抑制剂二苯基碘(DPI)共处理较ABA单独处理,根数分别降低15.2％和30.9％,根长分别降低24.1％和26％.进一步结果表明,与PEG处理相比,PEG+ABA处理的叶片气孔开度百分比、密度和相对电导率分别降低了24.2％、15.4％和14.2％,而相对含水量增加了25％.此外,PEG+ABA处理增加了外植体的渗透调节物质(脯氨酸、可溶性糖和可溶性蛋白)含量和过氧化物酶、多酚氧化酶和吲哚乙酸氧化酶的活性,降低了丙二醛含量.然而,内源H2O2清除剂CAT逆转了ABA的上述作用.可见,H2O2通过调节水分平衡、细胞膜稳定性、渗透调节物质含量和生根相关酶活性参与干旱条件下ABA促进不定根的发生.
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