Air pollution and its effects on plants in China.
Atmospheric pollution in China is mainly caused by human activities such as urbanization and industrialization. Such activities have increased in the last 10 years, and urban and industrial areas air pollution is typically a coal-smoke smog. Air pollution monitoring indicates that the quality of air in most cities continues to deteriorate. Simulation studies on the effects of air pollution typical of some urban and industrial areas on local crops and vegetables suggested that ambient concentrations of sulphur dioxide and fluoride could reduce their growth and yield by 5-25%. Fumigation studies on the physiological and biochemical responses of plants to air pollution demonstrated a reduction in chlorophyll content; inhibition of photosynthesis; increases in potassium leakage, stomatal resistance, respiration and proline; and increases in superoxide dismutase and perioxidase activity as the concentration and exposure time of sulphur dioxide and fluoride increase. Preliminary studies on the injury mechanisms of sulphur dioxide indicate that free radicles participate in the course of injury.