Effect Of Lanthanum On Soybean Seedlings Chlorophyll Exposed To Supplementary Ultraviolet-B Radiation

The effect of La(â…¢)on seeding chlorophyll was investigated under the elevated UV-B(280³20nm) radiation in laboratory condition. Soybean(Clycine max)"Kennong 18"was chosen as experiment material. The effect of the dosage and duration of La(â…¢)on the chlorophyll content of soybean seeding. And The effect of La(â…¢)on the soybean seeding under UV-B on: the content of chlorophyll; the biosynthesis and chlorophyll of chlorophyll; the breakdown of chlorophyll by light and oxygen;the ultrastructure of chloroplast. The result of research as follow:1 The low dosage(10³0mg·L^-1) of La(â…¢)increased the content of chl in the soybean seeding. When seedling was pretreated by 20mg·L-1LaCl3, the content of chlorophyll of soybean seedling was increased most,the degree of enhanced of chla>chlb; The high dosage of (≥60mg·L^-1)La(â…¢)depressed the conten of chl, the degree of depressed of chla>chlb. The 20mg·L^-1 was elected to be the best dosage of this thesis.2 When seedling was pretreated by La(â…¢),the content of:ALA,PBG,Proto-IX,Mg-Proto was increased,the process which Pchl turn to chl was accelerated. The La(â…¢) promote the protective effect of plant against UV-B stress effect on the PBG,Proto-IX,Mg-Proto and ALA. La(â…¢)can increased the activity of chlase, promote the protective effect of plant against UV-B stress on the activity of chlase.The pathway of chl biosynthesis was restrained on the condition of UV-B stress, and the restrained position is ALA→PBG。3 La(â…¢)can eliminate the O2- and H2O2 in the plants; increased the activity of AsA-POD; alleviate the chl breakdown which caused by light oxidation; alleviate the accumulate of O₂^- and H₂O₂ which caused by UV-B stress; alleviate the effect of light oxidation which caused by UV-B stress.4 When seedling was pretreated by La(â…¢), the thylakoid placed in an orderly arrangement and watched clearly. La(â…¢)can alleviate the effect of destroy on thylakoid which caused by UV-B stress. La(â…¢)change the location of chloroplast in the cell on the condition of UV-B stress; alleviate the effect of destroy on chloroplast membrane which caused by UV-B stress;the UV-B stress make the thylakoid placed in chaos arrangement and watched illegibly, La(â…¢)alleviate the effect of destroy on chloroplast structure which caused by UV-B stress.5 La(â…¢)can alleviate the effect of UV-B stress on chl metabolize and chloroplast structure. And the effect of La(â…¢)alleviate on low dosage UV-B(T1) is better than high dosage UV-B(T2).