Abstract: In order to investigate the resistance mechanism and purifying capacity of major afforestation tree species to sulfur dioxide (SO₂) pollution, Alnus cremastogyne was selected and studied. The results showed that: (1) The leaves appeared injury symptoms at the 14th and 7th day under SO₂ 4.29 mg·m^-3 and 8.57 mg·m^-3 treatments respectively; (2) With the increase of SO₂, the content of total chlorophyll (Chl), Chl a/b rate and net photosynthesis rate (Pn) decreased in the leaves, but stomatal conductance (Gs), transpiration rate (Tr) and intercellular CO₂ concentration increased first and then decreased, in addition, Pn was no significant difference between CK and treatment of SO₂ 4.29 mg·m^-3; (3) The content of proline (Pro), soluble sugar (SS), soluble protein (SP) and malonaldehyde (MDA) in the leaves rose gradually with increasement of SO2 concentration; (4) The POD and SOD activities in the leaves increased with SO2 increasing, but the CAT activity decreased first and then increased; (5)With the increase of SO₂, the sulphur content in the leaves increased. In conclusion, A. cremastogyne could adjust own stress protection system to adapt SO₂-polluted environment and maintain the normal growth, it could be planted in SO2 polluted areas as the large-scale use of afforestation tree species and achieve the goal of harnessing pollution.

Key words: SO₂, Alnus cremastogyne, physiological index, sulphur content

摘要： 采用人工模拟熏气法，研究SO₂胁迫下桤木Alnus cremastogyne的生理响应机制及净化能力。结果表明：(1)桤木叶片在SO2 4.29 mg·m^-3和8.57 mg·m^-3处理下分别在14 d和7 d时出现伤害症状；(2)随SO₂浓度增加，桤木叶片叶绿素总量、叶绿素a/b值和净光合速率呈下降趋势，其中净光合速率在SO₂ 4.29 mg·m^-3处理下与CK无显著差异，而气孔导度、蒸腾速率和胞间CO₂浓度呈现先增后降趋势；(3)叶片脯氨酸、可溶性糖、可溶性蛋白质、丙二醛含量均随SO₂浓度升高而增加；(4)叶片过氧化物酶和超氧化物歧化酶活性随SO₂浓度增加而升高，过氧化氢酶活性呈先降低后升高的趋势；(5)桤木叶片硫含量随SO₂浓度增加呈递增趋势。桤木幼树能通过调节自身保护机制应对低浓度SO2逆境胁迫并维持正常生长，可将其用作工厂附近或SO₂污染区域造林树种，以改善环境空气质量。

关键词: SO₂, 桤木, 生理指标, 含硫量