Mechanism Of Migration And Transformation Of Nano Selenium And Mitigates Cadmium Stress In Plants

Selenium is a trace element necessary for human,animal and plant.Appropriate amount of selenium can play a role in promoting plant growth and improving human immunity.In recent years,it has attracted widespread attention and has been used in large quantities for selenium biofortification.Nano selenium is an emerging fertilizer.Because of its unique physical and chemical property,it has the advantages of low toxicity and environmental friendliness compared with traditional sodium selenite and sodium selenate.There is a tendency to gradually replace traditional selenium fertilizer.Now most studies aim to reveal the mechanism of selenium promoting plant growth and regulating plant antioxidant enyme activities.Few study have explored the bioavailability and biotoxicity of selenium.Therefore,this research combine the promotion and inhibition of selenium on plant growth systemly,the valence transformation and distribution of selenium in plants,and the interaction between selenium and heavy metals,To achieve a comprehensive understanding of biological function of selenium.In this study,the typical monocotyledonous wheat(Triticum aestivum L.)and the dicotyledonous plant Chinese cabbage(Brassica chinensis L.)were studied.The exogenous application of different concentrations of Nano selenium and sodium selenite explored the plant.The effect of selenium on its physiological and selenium morphological change in normal growth and under external environmental stress.The main research contents and conclusions as follows:(1)The results showed that the alkali-soluble/water-soluble Se2-and organic selenium(SeCys,SeMet,MeSeCys)in various parts of wheat increased with the increase of external Nano selenium application,and the content of organic selenium in each part was increased.It accounted for more than 60%of the total selenium content in wheat,and SeMet is the main form of organic selenium.The content of Se4+ in various parts of wheat is leaf>root>shell>stem>seed,and the application of high concentration selenium promote wheat production.A small amount of Se6+ promote the conversion of Se4+ to other forms of selenium.This chapter explored the mechanisms of transformation,distribution,migration and storage of Nano selenium in wheat.(2)By applying different concentration of selenium to Chinese cabbage,it was found that the appropriate amount of Nano selenium can promote the growth of Chinese cabbage and chlorophyll synthesis.Increased the activity of antioxidant enzyme(SOD,POD.CAT)in leaf,but excessed Nano selenium had toxic effect on the growth of Chinese cabbage,such as decreased chlorophyll content and root activity,inhibited antioxidant enzyme activity,etc.,while sodium selenite is more toxicity than nano selenium.This chapter explored the bioavailability and biotoxicity of different concentration of selenium in Chinese cabbage,and provided technical support for better selection of suitable concentration of nano selenium as a selenium supplement.(3)Through the interaction experiment between Nano selenium and heavy metals,the mechanism of Nano selenium alleviating cadmium toxicity to plant in soil was explored.The results showed that the biomass,chlorophyll content.SOD and GSH-Px acti,vity of Chinese cabbage increased when low concentration of Nano selenium and Sodium selenite were applied under cadmium stress,The cadmium content in leaf and root can be reduced by more than 60%,indicated that proper selenium can promote plant growth under cadmium stress and enhance its ability to resist heavy metal toxicity,which provided theoretical basis and technical support for deep utilization and bioremediation of heavy metal contaminated soil.