The Effect of UV-B radiation and acid rain on physiological property and quality of lettuce

Acid rain and UV-B increasing is respectively one of global environment problem, which is the warm topic at present. The paper studied the effect of UV-B radiation and acid rain on physiological property and quality of lettuce under field condition. The results of physiologic index showed that UV-B radiation increasing resulted in reduction of chlorophyll-a, chlorophyll-b, chlorophyll-a+b, and transpiration in leaf. The more ultraviolet radiation increased, the more the decreasing degrees were influenced. At the same time, the content of flavonoid in leaf was increased with UV-B increasing. Acid rain also had different influence on chlorophyll and transpiration in leaf. While acid rain had little effect on the content of flavonoid in leaves. The results about quality showed that enhanced ultraviolet radiation increased the content of ascorbic acid, dissolve sugar and dissolve protein, but the more ultraviolet radiation increased, the more the content of dissolve sugar and ascorbic acid decreased, which there exists a limit of quality content . Acid rain increased the content of ascorbic acid, and the smaller pH was, the more the content of ascorbic acid; Acid rain increased the content of dissolve sugar and dissolve protein, and the smaller pH was, the more the content of dissolve sugar and dissolve protein decreased, but they became higher when exceeded to certain extent ;with PH decreasing the water content decreased. The effect of UV-B radiation was cooperated with acid rain on the only index of the content of flavonoid in leaf. The result showed that the effects under combined stress were significantly higher than single stress.