Abstract: The seedling growth and anti-oxidative system of two perennial grasses,Elymus nutans Griseb.and Poa crymophila Keng.,which play a dominant role in most grasslands in Qing-Tibetan Plateau,were studied under drought stress,UV-B radiation stress,and the combined stress,respectively.The results show that the two grasses had same defence mechanism and the similar reactions of two materials under all the stresses were detected.The height,leaf relative water content,leaf area,fresh weight,and dry weight decreased under the drought and UV-B radiation stress,respectively;at the same time, POD activity decreased and the activities of SOD,CAT,PRO and ASA increased.Under the combined stress,the fresh weight,dry weight,and leaf relative water content were higher than those under the drought stress,and meanwhile the height and leaf area were higher than those under the UV-B radiation stress.According to the above growth indices,the grasses had higher defending capability under the combined stress,which might be elucidated by the upheaval of Pro and ASA amounts under drought stress helping to defend UV-B stress and the increased amount of anti-oxidative materials under UV-B stress helping to get rid of the toxic materials caused by drought stress,and the same time,the concentration of many active proteins could upgrade the inner-osmotic pressure to keep water and further boost up the drought resistance ability.

Key words: Anti-oxidative system, Stress, Perennial grass, Drought stress, UV-B radiation stress

摘要： 在干旱胁迫、紫外线辐射胁迫及二者协同胁迫下,研究垂穗披碱草(Elymus nutans Griseb.)和冷地早熟禾(Poa crymophila Keng.)幼苗的生长和抗氧化系统的变化。结果表明:幼苗在不同逆境下抗氧物质和生长指标差异不明显,说明二者具有相同的防御机制;在UV-B辐射和干旱胁迫下,株高、叶片含水量、叶面积、鲜重和干重均呈下降趋势,POD(过氧化物酶)活性降低,SOD(超氧化物歧化酶)和CAT(过氧化氢酶)活性升高,Pro(脯氨酸)和AsA(抗坏血酸)含量升高;但在二者协同胁迫下,鲜重、干重、叶片含水量比干旱胁迫下均有所提高,株高和叶面积比UV-B胁迫下也有相应提高,证明在协同胁迫下,幼苗具有较强抵抗力;这可能是在干旱胁迫下脯氨酸(Pro)和抗坏血酸(AsA)显著增加增强了植株对UV-B辐射胁迫的抵抗力,同时在UV-B胁迫下植物产生大量的抗氧系统酶,因而有利于清理对干旱胁迫产生的有毒物质,同时有些活性蛋白等物质的产生将会增加细胞内渗透压,有利于保持水分,增强植物抗旱能力。

关键词: 抗氧化系统, 胁迫, 多年生牧草, 干旱胁迫, 紫外辐射胁迫