The effects of 0.2 μmol·L-1 exogenous 2,4-epibrassinolide (EBR) on the growth and reactive oxygen species metabolism of cucumber seedlings ('Jinyan 4' cucumber) under salt-alkaline stress (30 mmol·L-1 NaHCO3) were examined by hydroponics method. The results showed that NaHCO3 stress significantly induced production of O2-· and accumulation of H2O2 in leaves and roots, resulting in the increases of MDA content and electrolyte leakage. Under NaHCO3 stress, activities of superoxide dismutase, peroxidase, catalase, ascorbate peroxidase, dehydroascorbatereductase, monodehydrodroascorbate reductase, and glutathione reductase as well as contents of ascorbic acid and glutathione were firstly increased and then decreased with progress of stress time. Exogenous EBR application significantly increased the activities of antioxidant enzymes and contents of antioxidants as well as the ratio of AsA/DHA (dehydroascorbic acid) and GSH/GSSG (L-glutathione oxidized) in leaves and roots of cucumber under NaHCO3 stress. Such changes improved the redox hemostasis in plants, reduced the level of reactive oxygen species, and alleviated the membrane lipid peroxidation. Together, they increased the alkaline tolerance of cucumber seedlings.
以‘津研四号’黄瓜为试材,以30 mmol·L-1 NaHCO3模拟盐碱环境,采用水培法研究了0.2 μmol·L-1外源2,4表油菜素内酯(2,4-epibrassinolide,EBR)对盐碱胁迫下黄瓜幼苗生长和活性氧代谢的影响.结果表明: NaHCO3胁迫显著诱导了叶片及根系中O2-·的产生和H2O2的积累,导致丙二醛含量和电解质渗透率提高.NaHCO3胁迫下,超氧化物歧化酶、过氧化物酶、过氧化氢酶、抗坏血酸过氧化物酶、脱氢抗坏血酸还原酶、单脱氢抗坏血酸还原酶、谷胱甘肽还原酶活性及还原型抗坏血酸、还原型谷胱甘肽含量随胁迫时间延长呈现先升后降的趋势.外源EBR显著提高了NaHCO3胁迫下黄瓜叶片和根系中抗氧化酶活性、抗氧化物质的含量以及AsA/DHA(双脱氢抗坏血酸)和GSH/GSSG(氧化型谷胱甘肽)比值,维持了植株内的氧化还原平衡,降低了活性氧积累水平,缓解了膜脂过氧化,从而提高了黄瓜幼苗的盐碱耐受性.
Keywords: AsA-GSH cycle; antioxidation; cucumber; reactive oxygen species; salt-alkaline stress.