Abstract: Effect of La on the chlorophyll content of Soybean(Glycine max) seedling under elevated ultraviolet-B radiation(UV-B,280~320 nm) was studied.After exposing of seedling to UV-B radiation for 5 days,the content of chlorophyll a and b of soybean seedling was decreased by 10.20% and 12.18% respectively,compared with the control.The dosage of radiation had good direct correlation with change of chlorophyll content.When seedling was pretreated by 20mgL~(-1)LaCl_(3),the content of chlorophyll a and b of soybean seedling under UV-B stress was increased by 4.82% and 4.53% respectively.It can be concluded that the rare earth can elevate the content of chlorophyll and promote the protective potential against to UV-B stress.Exposed to UV-B radiation by 0.45 Wm~(-2),the injury of seedling was more and more serious,and the organs of plant were damaged finally.By 0.15 Wm~(-2),the chlorophyll a content was decreased by 13.14%;chlorophyll b was no change.La can promote the protective effect of plant against UV-B stress and alleviate the injury to plant.

Key words: Lanthanum(La), Lanthanum(La), Ultraviolet-B radiation, Chlorophyll