Acid rain types in China vary gradually from sulphur-rich acid rain to nitric-rich acid rain gradually in China, however, the systematic researches on the differences of plants resistance under the varied acid rain types are still scarce. In this paper, spruce (Picea asperata) leaves were treated with both sulphur-rich acid (SRA) solution and nitric-rich acid (NRA) solution, and the damage mechanisms of cell membrane and its protective systems in leaves under the acid stresses were compared. The results showed that in a range of acidity from pHS to pH3, the cell membrane damage and lipid-peroxidation were not remarkable. However, when the acidity of the acid solution increased to pH2. 0 and pHl.0, the activities of antioxidant enzymes, chlorophyll content and membrane stability index (MSI) reduced significantly. When the acidity was as higher as pHl.0, the SOD activity reduced more sharply in the NRA stress than that in the SRA stress, while the activities of CAT and POD showed no significant changes. The results also showed that the levels of reactive oxygen species and the ehtylene-producing rate of ethylene were much higher, while the content of polyamines, chlorophyll, carotenoid, proline and soluble sugar were significantly lower under NRA stress than that under SRA stress in spruce leaves when the acidity was as high as pHl. 0. These results were closely related with the fact that the oxidative ability of the dilute nitric acid is much higher than that of the dilute sulphur acid, and this difference between the two types of stress is consistent with their decline of membrane stability index ( MSI) and the increment of MDA content under the same high acidity (pH2. 0, pHl.0). In general in comparison with SRA stress, NRA stress had higher oxidative ability under the acidity of pH2. 0 and pHl.0, the protective systems in anti-oxidative enzymes and polyamines were deteriorated more severly, thus the damage caused by NRA stress was aggravated more than SRA stress in the sprue leaves.%以含有较多硫酸的硫酸、硝酸混合液( sulphur-rich acid,SRA)和较多硝酸的硫酸、硝酸混合液(nitric-rich acid,NRA)浸泡云杉针叶,研究这2种类型酸溶液在不同酸度下对云杉叶细胞膜及其保护系统损伤的机制.结果 表明:酸胁迫24h,当溶液酸度在pH5.0 ～3.0时,细胞膜受伤害程度和脂质过氧化程度较低；当溶液酸度增加至pH2.0和pH1.0时,云杉叶抗氧化酶活性、叶绿素含量和细胞膜稳定指数显著降低.对比这2种类型酸胁迫,在酸溶液的酸度增加至pH1.0时,CAT和POD活性在2种酸胁迫间没有显著差别,但NRA酸胁迫云杉叶片SOD活性的下降幅度显著大于SRA酸胁迫.这2种类型的酸胁迫以NRA酸胁迫的云杉叶活性氧水平和乙烯产生速率较高,而多胺含量、叶绿素含量、脯氨酸含量和可溶性糖含量较低.上述结果与稀硝酸相对稀硫酸具有较强的氧化性密切相关,并与在强酸度下(pH2.0,pH1.0)NRA酸胁迫相对降低云杉叶细胞膜稳定指数和提高MDA含量的特点相一致.在较强的酸度下,NRA酸胁迫比SRA酸胁迫对云杉叶表现出较强的氧化能力,从而在更大程度上损害其抗氧化酶、多胺、类胡萝卜素等构成的细胞膜保护系统,加重细胞膜的损伤.
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