Abstract: To study the effects of different drought resistant Elymus sibiricus materials on the accumulation and removal of reactive oxygen species (ROS) in seedlings under drought stress,and to provide certain theoretical basis for the research on the physiological mechanism of drought resistant Elymus sibiricus and the selection and breeding of drought resistant materials. The seedlings of two Elymus sibiricus materials with significant differences (Q stands for the strong drought resistant material,S stands for the weak drought resistant material) in drought resistance were cultured with sand. When the seedlings grew to 2 leaves and 1 shoot,1/2 Hoagland nutrient solution containing 20% PEG 6000 (W/V) was used for stress treatment,and the two materials without PEG treatment were used as control. Samples were taken at 7 d,14 d and 21 d after treatment and the indexes were measured,respectively. The activity of antioxidant enzymes was also measured. The results showed that during the whole stress process,the reduction of plant height,relative water content (RWC) and the increase range of ROS,malondialdehyde (MDA) of QD were lower than that of SD,and the increase range of antioxidant enzyme activity and the ratio of antioxidant substance were higher than that of SD. Compared to their respective controls,the plant height of QD and SD decreased by 39.11% and 55.20%,respectively,after 21 days of drought stress treatment. The RWC has dropped by 78.34% and 84.52%. The O₂^·- content increased by 235.71% and 323.03%. H₂O₂ content increased by 126.19% and 234.88%. MDA content increased by 318.99% and 434.81%. Superoxide dismutase (SOD) activity increased by 156.20% and 83.83%. Catalase (CAT) activity increased by 32.39% and 30.50%. Ascorbate peroxidase (APX) activity increased by 58.10% and 172.89%. Dehydroascorbate reductase (DHAR) activity increased by 66.54% and 11.38%. Glutathione reductase (GR activity) increased by 227.07% and 130.29%. The decrease of ASA/DHA was 52.51% and 73.69%. The decrease of GSH/GSSH was 40.94% and 61.43%. In summary,the reduction of plant height,RWC and ROS accumulation and membrane lipid peroxidation degree of strong drought resistant material were lower than that of weak drought resistant material. In response to drought stress,SOD,CAT and GR were dominant in the Elymus sibiricus with strong drought resistance,while SOD,CAT and APX were dominant in the Elymus sibiricus with weak drought resistance. But overall,the strong drought-resistant Elymus sibiricus showed a stronger antioxidant defense system.

Key words: Elymus sibiricus L., Drought stress, ROS, Antioxidant substance

摘要： 为探究不同抗旱性老芒麦（Elymus sibiricus L.）材料对干旱胁迫下幼苗活性氧（Reactive oxygen species，ROS）积累和清除的影响，从而为老芒麦抗旱生理机制的研究及抗旱材料的选育提供一定的理论基础，本试验选用抗旱性差异明显的2份老芒麦材料（抗旱性强的材料，记为Q，处理组QD，对照组QC；抗旱性弱的材料，记为S，处理组SD，对照组SC），采用砂培法培养材料，待幼苗长到2叶1心时，用含有20% PEG 6000（W/V）的1/2 Hoagland营养液进行胁迫处理，2份材料的对照正常培养。在处理7 d、14 d和21 d取样，分别测定各项指标。试验结果表明，在整个胁迫过程中，QD的株高、叶片相对含水量（Relative Water Content，RWC）降幅及ROS和丙二醛（Malondialdehyde，MDA）增幅均低于SD，但是抗氧化酶活性的增幅以及抗氧化物质的比值高于SD。与各自的对照相比，干旱胁迫21 d后，QD和SD的株高分别下降39.11%和55.20%；RWC分别下降78.34%和84.52%；O₂^·-含量分别增加235.71%和323.03%；H₂O₂含量分别增加126.19%和234.88%；MDA含量分别增加318.99%和434.81%；超氧化物歧化酶（Superoxide dismutase，SOD）活性分别增加156.20%和83.83%；过氧化氢酶（Catalase，CAT）活性分别增加32.39%和30.50%；抗坏血酸过氧化物酶（Ascorbate Peroxidase，APX）活性分别增加58.10%和172.89%；脱氢抗坏血酸还原酶（Dehydroascorbate Reductase，DHAR）活性分别增加66.54%和11.38%；谷胱甘肽还原酶（Glutathione Reductase，GR）活性分别增加227.07%和130.29%；抗坏血酸（Ascorbic Acid，ASA）和脱氢抗坏血酸（Dehydroascorbic acid，DHA）比值（ASA/DHA）的降幅分别为52.51%和73.69%；谷胱甘肽（Glutathione，GSH）和氧化型谷胱甘肽（Glutathiol，GSSH）比值（GSH/GSSH）的降幅分别为40.94%和61.43%。综上可得，干旱胁迫下抗旱性强的材料株高和RWC降幅、ROS积累和膜脂过氧化程度显著低于抗旱性弱的材料；抗旱性强的老芒麦响应干旱胁迫时以SOD、CAT和GR为主，抗旱性弱的老芒麦响应干旱胁迫时以SOD、CAT和APX为主；但是整体来看，抗旱性强的老芒麦表现出更强的抗氧化防御系统。

关键词: 老芒麦, 干旱胁迫, 活性氧, 抗氧化物质