Effects Of Spraying Lanthanum Chloride ?LaCl₃? On Physiological Characteristics Of Medicago Sativa Under Enhanced UV-B Radiation

The enhance UV-B radiation will inhibit photosynthetic characteristics of plant,damage cell membrane and the structure of biological membrane systems.The suitable concentration of lanthanum can improve the protective function of cell membrane,enhance the resistance of plants to adverse environment,Medicago sativa which known as "the king of grass",as a legume pasture,is widely cultivated in China and the world.In this paper,we had Medicago sativa as test materials to study the effects on physiological characteristics of Medicago sativa enhanced UV-B radiation(5%and 10%)on the growth period where Lanthanum chloride(LaCl3)(30.60 and 90 mg·L-1)was sprayed.in the branching stage and the early flowering stage,respectively.The results show:With UV-B radiation was enhanced by 5%,and the LaCl3 was sprayed in the branching stage.In the early flowering stage,the net photosynthetic rate(Pn).PS?maximum photochemical quantum yield(Fv/Fm),superoxide anion free radical(O2-·),hydrogen peroxide(H2O2),superoxide dismutase(SOD),catalase(CAT)and peroxidase(POD),proline(Pro),soluble sugar content and aboveground biomass of Medicago sativa showed a significant increased treads(P<0.05),and chlorophyll content,electron transport rate(ETR),relative osmotic conductivity,malondialdehyde(MDA),carotenoid(Car)and soluble protein of Medicago sativa showed a significant increased treads(P<0.05)under sprayed LaCl3 with the concentrations of 30 mg·L-1.In the flowering stage,Pn,Fv/Fm,ETR,SOD,CAT,POD,Pro and aboveground biomass of Medicago sativa showed a significant increased treads(P<0.05).and the other indexes showed a significant decreased treads(P<0.05).In the mature stage.Pn,Fv/Fm,ETR,SOD,CAT,POD,Pro,soluble sugar and aboveground biomass of Medicago sativa showed a significant increased treads(P<0.05),and the other indexes showed a significant decreased treads(P<0.05).With the LaCl3 was sprayed in the flowering stage,chlorophyll content,Pn,Fv/Fm,ETR,SOD,CAT,POD.Car,soluble sugar,Pr and aboveground biomass of Medicago sativa showed a significant increased tread in the whole growth period(P<0.05).In addition,spraying LaCl3 with the concentrations of 60 mg-L"1 also had a protective effect but was inferior to that of 30 mg·L-1,and 90 mg·L-1 damage Medicago sativa leaves in conjunction with the effect of UV-B radiation.Therefore,sprayed LaCl3 with the concentrations of 30 mg·L-1 can improve the enzyme activity,enhance the ability to scavenge reactive oxygen species,and alleviate the oxidative damage and membrane lipid peroxidation caused by 5%of UV-B radiation.With UV-B radiation was enhanced by 10%,and the LaCl3 was sprayed in the branching stage.In the early flowering stage,Pn,Fv/Fm,SOD,CAT,POD,Pro,soluble sugar content and aboveground biomass of Medicago sativa showed a significant increased treads(P<0.05),the other indexes showed a significant decreased treads(P<0.05)under sprayed LaCl3 with the concentrations of 60 mg·L-1.In the flowering stage,Fv/Fm,SOD,CAT,POD,Car,Pro,soluble sugar and aboveground biomass of Medicago sativa showed a significant increased treads(P<0.05),and the other indexes showed a s,ignificant decreased treads(P<0.05).In the mature stage,Fv/Fm,ETR,H2O2,SOD,CAT,POD,Car,Pro,soluble sugar and aboveground biomass of Medicago sativa showed a significant increased treads(P<0.05),and the other indexes showed a significant decreased treads(P<0.05).With the LaCl3 was sprayed in the flowering stage,chlorophyll content,Pn,Fv/Fm,SOD,CAT,POD,Car,soluble sugar,Pr and aboveground biomass of Medicago sativa showed a significant increased tread in the whole growth period(P<0.05).In addition,spraying LaCl3 with the concentrations of 30 mg·L-1 also had a protective effect but was inferior to that of 60 mg·L-1,and 90 mg·L-1 damage Medicago sativa leaves in conjunction with the effect of UV-B radiation.Therefore,sprayed LaCl3 with the concentrations of 60 mg·L-1 can improve the enzyme activity,enhance the ability to scavenge reactive oxygen species,and alleviate the oxidative damage and membrane lipid peroxidation caused by 10%of UV-B radiation.The T test showed that during the early flowering stage of sprayed LaCl3 has obvious effect to reduce UV-B radiation,and the relief stage was in first stage.