| The hydroponic culture experiment of soybean seedlings were conducted to invested effect of Cerium(Ⅲ) on content and disposition of mineral elements in different tissue on different growth stage.The experiment condition is as follows:The levels of UV-B radiation were 0.15 and 0.45 W·m-2,which were imitated artificially.The seedlings were irradiated for 6h,from 9:00 to 15:00,for a total of 9 days which were exposured to lamp 5 days and 4 days recovery time. The concentration of Cerium(Ⅲ) solution was 20mg·L-1.There were 6 sample sets in the experiments:controls(sprayed with deionized water),Ce(Ⅲ)(sprayed with CeCl3 solution), T1(irradiated with 0.15 W·m-2 UV-B),T2(irradiated with 0.45 W·m-2 UV-B), Ce(Ⅲ)+T1(sprayed with CeCl3 solution and then exposed to 0.15 W·m-2 UV-B radiation),and Ce(Ⅲ)+T2(sprayed with CeCl3 solution and then exposed to 0.45 W·m-2 UV-B radiation).The results showed that UV-B radiation can effect content and disposition of mineral element in soybean seedlings;the effect of inhibition on plant in is more obviously in high dose of UV-B radiation than that in low dose.Ce(Ⅲ) can alleviate the damage of UV-B radiation on the plant and its protective effect against low UV-B radiation was superior to that of high UV-B radiation.The results showed that effect of rare earth elements on plant is "low concentration promotion,high concentration inhibition".It is to say that low concentration CeCl3 can promote soybean' growth,but high concentration have damage to soybean.So we change soluble protein content which respond N metabolism overally and photosynthetic rate which respond assimilation of plant as index to get that the optimum concentration of Cerium(Ⅲ) solution is 20 mg·L-1.CeCl3(20mg·L-1) can promote soluble protein content and net photosynthetic rate in soybean seedlings.Nitrate reductase activity,nitrate nitrogen and phosphor content in soybean seedlings' leaves in UV-B treatment were more decreased than those with CK.Nitrate reductase activity was inhibited by UV-B stress so much that nitrate nitrogen and phosphor content were decreased,but also inhibitory action is stronger by high intensity and long time UV-B stress;suitable concentration CeCl3(20mg·L-1) could promote absorption nitrate nitrogen and phosphor content in soybean seedlings to alleviate the decrease of nitrate nitrogen and phosphor content.Supplement of UV-B restrain absorption of macroelement(K,Ca,Mg) and traceelement (Cu,Mn,Mo,Zn,Fe) in soybean seedlings.Pretreatment with Cerium(Ⅲ) can increase absorption of mineral element(N,P,K,Ca,Mg,Cu,Mn,Fe,Zn,Mo)content in roots,stem and leaves on seedling stage,growing stage and pod setting stage.It suggest that Ce(Ⅲ) can release mineral element loss exposing to UV-B to promote growth of soybean seedlings.Plant roots provide requirement of moisture content and mineral matter in aerial parts.It is main organ to gain moisture content nutrient substance from living environment. Supplement of UV-B radiation decrease root activity,amplitude reduction and intensity of radiation show dose-effect relation.Rate of decay of root activity was released in Ce(Ⅲ)+UV-B treatment and root activity was increased by 24.3%in Ce(Ⅲ) treatment compared with control.It suggest that Ce(Ⅲ) can eliminate decrease of root activity exposing UV-B;it can raise root activity and promote absorption on mineral nutrient substance in roots.On different growth and development stage,difference of mineral element content in ass tissue was observed,which was affected by supplement of UV-B.Pretreatment with Cerium(Ⅲ)can raise mineral element content in soybean seedlings on different growth and development stage;it can alleviate damage of UV-B radiation on the soybean seedlings; auxoaction by Cerium(Ⅲ)on mineral element content in different stages maintain 14.0%.The content of mineral elements in soybean is different with different growth stage and different organism.Mineral element content of soybean is different in different growth and development stage and in different ass tissue apparently and sharply.It suggested lasting effect on soybean seedlings by Ce(Ⅲ) is well,the result is obvious to 9 day.Ce(Ⅲ) can promote mineral element transferring to different tissues;different promoting effect on absorption of mineral element in different tissues was observed.
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