Abstract: The study on the physiological activities of bean leaves at different position on stem showed that,under ultraviolet radiation，the photosynthesis and transpiration rate of leaves increased first and decreased then.After 3 h ultraviolet radiation,the inhibition rate of photosynthesis was increased with increasing leaf position.The stomatal conductance and intercellular CO₂ of the first leaf enhanced slightly,while those of the second and third leaves enhanced first but decreased then.Ultraviolet radiation made the chlorophyll content decreased first and enhanced then,and made the MDA content enhanced significantly.The POD activity under ultraviolet radiation enhanced first and decreased then,and after 3 h ultraviolet radiation,the POD activity in the first leaf was 26.9% lower than the control.Ultraviolet radiation slightly raised the SOD activity of the first leaf,but sharply inhibited the SOD activity of the second and third leaves.

Key words: Swamp wetland, Vegetable organs, N content dynamics