[Effect of the combination of cadmium and UV-B radiation on soybean growth]

This paper studied the characteristics of soybean growth under the stress of Cd, UV-B radiation and their combination. The results showed that UV-B radiation gave a more pronounced inhibition on soybean growth than cadmium. Under UV-B radiation, the internode differentiation and elongation were inhibited, the internode and plant height were reduced, and the activities of SOD and POD had an apparent increase. Cd2+ could antagonize the effect of UV-B radiation on POD activity, and inhibit indole-3-acetic acid (IAA) oxidase activity. A significant decrease of POD and IAA oxidase activities in soybean was detected when exposed to combined UV-B and Cd2+, compared with UV-B radiation only. The decrease of POD and IAA oxidase activities was related to the increase of IAA contents and photosynthetic activity, which might account for the increases of biomass and plant height. Moreover, the combined stress enhanced the inhibition of root growth, and significantly decreased root length. The IAA oxidase and POD activities and photosynthesis rate might be the crucial factors determining the pattern of soybean growth under the stress of Cd2+ in combination with UV-B radiation.