| In this study corn seedling was used as experiment-material. Effect of growth and metabolism of corn seedling under cadmium stress was studied through water culture experiment. And with lanthanum as adjustment reagent, protective effect of Lanthanum on corn seedling was studied.The results showed that corn seedling was harmed by Cd2+and its height ,main root became shorter, leaf area turned smaller than before, fresh and dry weight of leaf , stem and root decreased. Furthermore,physiological and biochemical characteristic of seedling changed greatly , chlorophyl content dropped, cell membrane permeability , the malony dialdehyde (MDA) content , activities of catalase (CAT) ,superoxide anion content and hydrogen peroxide content were increased. And with higher concentration of Cd2+, the damage became more serious. When 20mg/L La3+ was used to spray on corn seedling under cadmium stress one time, growth and metabolism of seedling was obviously reconditioned and the damage of Cd2+ pollution was reduced. It is proved by the experiment that La can improve chlorophyll content and keep the activities of CAT of corn seedling to control superoxide anion content and the hydrogen peroxide content,and reduce cell membrane permeability and content of MDA.Effect of La3 + ion on the structure and activity of catalase , as well as the chemical process of catalase interacting with La3+ ion were investigated by a combination of ultraviolet-visible, fluorescence, synchronous fluorescence, FT-infrared and X-ray photoelectron spectroscopic techniques. The results indicated that La3+ ion could interact with O and/or N groups in polypeptide chain of catalase , leading to the change of electron density of S , O and N atoms in catalase , meanwhile , making the heme active center of catalase be towards high spin state and more flexible , and causing some extent of conformational change of catalase , altering the folding state of the whole molecule , thereby changing the catalytic activity of catalase protein.
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