| Nowadays CFCs, a great amount of pollutant gases and human activities have caused the depletion of the stratospheric ozone layer and increased the intensity of ultraviolet-B radiation incident at the ground. This has been one of the most critical environmental problems across the whole world. At early time, researchers had done much work on the effects of UV-B on plant life, but most experiments were conducted under laboratory conditions. Field experiments were numbered and the results were not consistent with those from laboratory studies. In this study, a modulated lamp system for solar UV-B supplementation was used to provide extra 50% UV-B intensity than the ambient level as UV-B supplementation treatments. Reduced UV-B treatments were designed by covering UV-filtering films at the top of rice plants to screen 20% UV-B intensity of the ambient radiation. We analysed the effects of UV-B radiation on endogenesis hormone contents, chlorophyll contents, the anatomy of leaves and seed qualities by UV-B supplementation experiment and UV-B filtering experiment. Our results showed the following:(1) The heights of plants did not changed significantly in both UV-B supplementation experiment and reduced UV-B experiment. It was obvious that UV-B radiation affects little on the plant height in field conditions.(2) Under enhanced UV-B radiation, IAA, GA3, Zt and ABA contents were affected little, but contents of chlorophyll a and chlorophyll b both decreased significantly. Under reduced UV-B radiation, contents of IAA and GA3 at reduced UV-A+UV-B treatment significantly decreased compared with those at the ambient control . In particular, contents of GA3 and Zt decreased remarkably at reduced UV-A+UV-B treatment compared with those at reduced UV-A treatment. Chlorophyll a and total...
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