中文摘要：

酸沉降及变温条件下,植物会对胁迫产生一定的生理响应。通过人工酸沉降,测定酸胁迫下白三叶在变温条件下叶片可溶性蛋白、丙二醛（MDA）及抗氧化酶活性的变化规律。结果表明,酸沉降胁迫下,叶片MDA、过氧化物酶（POD）、超氧化物酶（SOD）升高,分别升高0.60%~18.82%、10.34%~24.47%、0.09%~18.11%,而可溶性蛋白含量降低2.85%~24.18%,过氧化氢酶（CAT）活力变化趋势不明显;在融冻胁迫下,叶片抗氧化酶、可溶性蛋白随温度下降先增高后降低,最大值出现在-5℃,MDA呈上升趋势,p H组、CK组最大值均出现在-15℃,分别为4.04、3.97μmol/L。在冻融胁迫下,POD随温度升高而上升,SOD和可溶性蛋白先升高后下降,CAT活力先下降后趋于平稳,MDA含量持续下降。白三叶通过快速激活抗氧化酶活力和积累丙二醛以抑制膜脂过氧化在酸沉降和冻融胁迫上的适应,是未来值得推广的园林绿色植物。

英文摘要：

Acid deposition and temperature variation stress condition could be the formation of physiological characteristics of plants in response to stress. Taking the white clover of the tolerant plants, which were determined by artificial acid deposition stress, the changes in the contents of soluble protein,malondialdehyde （MDA）,peroxidase（POD）,catalase（CAT） and superox- ide（SOD） activity in the leaves of white clover was investigated under freezing-thawing stress. The results show that MDA, POD and SOD in the leaves of white clover were higher with acid deposition stress, Respectively increased by 0.60%~ 18.82%,10.34%~ 24.47%,0.09%~18.11%. Instead, the soluble protein content of acid stress group was reduced by 2.85%- 24.18%. There was no significant difference about the CAT activity. Antioxidant enzymes activity and soluble protein contents in the leaves of white clover increased firstly and then decreased with the decrease of temperature in the thawing-freezing stress phase,which reached the highest value at -5 ~C. The content of MDA showed an upward trend, the maximum value of pH group and CK group occurred in -15 ~C, respectively 4.04 tzmol/L, 3.97 txmol/L.With the increasing of temperature, POD increased during the freezing-thawing stage. SOD and protein content increased firstly and then decreased. The activity of CAT decreased firstly and then tended to stable. The content of MDA was on the decline. White clover inhibited damage of membrane lipid peroxidation by activating antioxidant enzyme system. It is suggested that white clover had higher capability to adapt to freezing-thawing cycle and acid deposition stress,which could be a good landscaping species in future application and popularization.