Abstract: The sensitivity of plant to SO2 is a complicated and comprehensive character formed by the interactions of many factors, and often used to qualitatively describe air environmental quality. In this paper, the leaf appearance symptoms of plants exposed to different concentration SO2 were observed. The results showed that different plants had different sensitivity to SO2. The symptoms of plants exposed to low SO2 concentration for a long time were similar with those exposed to high SO2 concentration for a short time. The cell membrane permeability (electrical conductivity) of plants could directly reflect the damaged degree of plants. Based on the integrated data of plant appearance symptoms and physiological/biochemical indicators, a quantitative bio-evaluation model of air quality was established, which provided a basis for monitoring and evaluating atmospheric environment by plants.

Key words: Hilly area, Plum orchard, Intercrop, Ecological effect