Effects Of Short-term Supplementation Of UV-B Radiation On Seed Germination And Seedling Physiological Characteristics Of Saussurea Iodostegia Hance

UV-B(280-320 nm)radiation is an important component of the solar radiation spectrum which can partially reach the surface of the earth through the atmosphere.In recent years,Ozone depletion content like the Chlorinated hydrocarbons in human daily life,which are unreasonable in use and emissions have caused the ozone depleted,and even be destroyed.It makes the UV-B radiation that reach the surface of the earth increased.UV-B radiation will have effect on the plants,for example,biological macromolecules like plant DNA and nucleic acids will be destroyed;The morphological and physiological function of plant also will be affected,and even affect the whole ecosystem.The thinning ozone layer and the increasing ultraviolet have become one of the biggest concerns today.Qinghai-Tibet Plateau is one of the most sensitive areas in climate all around the world,and the UV-B radiation above it also increasing.As for the research materials,this article selects the S.iodostegia which is distributed in eastern region of the Qinghai-Tibet Plateau.We determined the seed germination,physiological and biochemical indicators,chlorophyll fluorescence parameters,reseached the law of S.iodostegia response to increasing UV-B radiation,investigated the physiological adaptation mechanism of the species and provided a theoretical basis for certain vegetation changes under increasing UV-B radiation on the Qinghai-Tibet Plateau area.At the same time,it also has important practical significance for the recovery of degraded grassland.The results are as following:1.To compared with the control group(without irradiation treatment),S.iodostegia seeds which treated by short-term supplement UV-B radiation indicated both germination index and germination rate were obviously decreased,and the longer seeds be treated,the lower germination index and germination rate will be.Seed germination appear delay phenomenon.2.Short-term supplement UV-B radiation inhibited the synthesis of chlorophyll a,chlorophyll b,total chlorophyll and soluble protein in the seedlings of S.iodostegia.UV-B radiation could promote the content of carotenoid,MDA,activity of SOD and CAT,also increase the soluble sugar content.3.The content of UV absorbing substances remained unchanged under short-term supplement UV-B radiation.4.Short-term supplement UV-B radiation can makes plant PS?system hurt and inhibits electron transfer.It reduced the values of F_o(initial fluorescence),F_m(the maximum fluorescence),F_v/F_m(PS II,the largest light quantum chemical yield),?PS(II)(actual photochemical efficiency),qP(photochemical quenching coefficient),and ETR(relative electron transfer rate)on the S.iodostegia leaf,while consumed redundant light energy by form of heat and reduce light oxidation,and protect photosynthetic mechanism through non photochemical quenching.The value of NPQ(non photochemical quenching)rise.In summary,the short-term supplement UV-B radiation,to a certain extent,destroyed the purple photosynthetic apparatus of S.iodostegia,reduced its photosynthetic capacity,but the plant physiological index of S.iodostegia by coordination of the body,improve their resistance to UV,so as to adapt to the plateau stress environment.Which adapts to the UV stress environment of the plateau,so that the plants can become the dominant species or common species in the region.