Abstract: This study was conducted to determine the influence of the exogenous EBR (24-Epibrassinolide) on the antioxidant system and osmolytes of Tibetan wild-type E. nutans seedlings under cold stress. The results showed that the biomass of E. nutans increased with the low concentration of EBR but decreased with high concentration,while the relative conductivity of leaves showed opposite trend. 1 μmol·L^-1 EBR had the best cold tolerance. Compared with control,cold stress resulted in the significant increase of SOD,GR,and APX activity and the slight suppression of POD and CAT activity. the stressed plants further increased the CAT,APX,and GR activities after EBR treated,while SOD activity had no significant change. In addition,exogenous EBR caused a significant increase in AsA,GSH,and free proline concentrations under cold stress,whereas reduced the accumulation of malondialdehyde (MDA) and superoxide anion radical. Therefore,spraying EBR could significantly increase the activity of antioxidant system,the accumulation of proline and the scavenging ability of reactive oxygen species under cold stress,alleviate cold-induced oxidative damages,and then enhance the E. nutans cold tolerance.

Key words: 2,4-epibrassinolide, Low temperature stress, Elymus nutans, Antioxidant system, Osmotic adjustment substance

摘要： 本研究以西藏野生垂穗披碱草（Elymus nutans Griseb.）为试材，采用叶面喷施2，4-表油菜素内酯（Epibrassinolide，EBR）的方法，探讨EBR对低温胁迫下西藏野生垂穗披碱草幼苗抗氧化保护和渗透调节的影响。结果表明，喷施不同浓度EBR导致垂穗披碱草幼苗生物量随浓度增加而升高，但高浓度下又有降低的趋势，而叶片相对电导率则呈相反变化趋势，其中1 μmol·L^-1的EBR处理抗寒效果最好。低温胁迫下，抗氧化酶（抗坏血酸过氧化物酶，谷胱甘肽还原酶，超氧化物歧化酶）活性显著高于CK，而过氧化氢酶和过氧化物酶活性低于CK，EBR处理后抗氧化酶活性进一步增加，同时叶面喷施EBR提高了低温胁迫下垂穗披碱草幼苗抗坏血酸、谷胱甘肽和游离脯氨酸含量，降低了丙二醛和超氧阴离子自由基的积累。因此，低温胁迫下喷施EBR能显著提高抗氧化系统活性和渗透调节物质脯氨酸的积累，增加活性氧的清除能力，减轻低温引起的膜脂过氧化，从而增强垂穗披碱草的耐寒性。

关键词: 2, 4表-油菜素内酯, 低温胁迫, 垂穗披碱草, 抗氧化系统, 渗透调节物质