Abstract: In order to investigate the resistance mechanism of Taxus chinensis var. mairei to sulfur dioxide (SO₂) pollution, one-year-old potted seedlings were grown in an enclosed fumigation chamber, and the concentration of SO₂ was set as 5, 10, 20 and 40 mg·m^-3 for various durations. Our results showed that the membrane permeability, the contents of  malondialdehyde (MDA), freeproline and soluble sugar were enhanced with the increase of SO₂ concentration and duration, while the contents of chlorophyll a and b decreased. The injury symptoms in leaves were first observed at 20 mg·m^-3 SO₂ after 5-day exposure. Under the same experimental duration, the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) were induced greatly at the lower SO₂ concentrations and then decreased at the higher SO₂ concentrations. The activities of SOD and APX were induced at 5 mg·m^-3 SO₂, while those of peroxidase (POD) and catalase (CAT) were induced at 10 mg·m^-3 SO₂. Under the 40 mg·m^-3 SO₂ stress, the activities of SOD, CAT, POD, and APX were significantly decreased in comparison with those in the control during the whole experimental periods. Our results suggest that Taxus chinensis var. mairei can adapt to 10 mg·m^-3 SO₂polluted environments with no obvious phenotypic injury through its own stress protection system to improve resistance to SO₂, therefore this species can be planted in SO₂ polluted areas.

Key words: carbon metabolic index, degradation, soil microbial biomass C and N, alpine meadow, enzymes