| China is the country with the most abundant antimony(Sb)resources in the world,and its mining and use have caused serious pollution to the environment.In this article,the highly enriched plant Pteris vittata L.found in the antimony mining area was taken as a research object to explore the changes of antimony content in Pteris vittata L.and the composition as well as the content of organic acids,amino acids and soluble sugars in root exudates under different antimony concentrations.Besides,the components that may affect the absorption and transportation of antimony in Pteris vittata L.were found from the organic acids and amino acids secreted by the roots.By carrying out the exogenous addition experiment and analyzing the effects of exogenous root exudates on physiological and biochemical characteristics,antimony content in vivo,antimony binding forms in cells,soil pH and antimony forms of Pteris vittata L.,the possible mechanism of root exudates on antimony absorption and accumulation of Pteris vittata L.was discussed.Main conclusions are as follows:(1)The content of antimony in roots,stems and leaves of Pteris vittata L.increased significantly with the increase of antimony stress concentration,and the order was as follows: root > stem > leaf.The proportion of antimony in the root reached 89%-96%,indicating that the roots are the main part of Pteris vittata L.to accumulate antimony.(2)The contents of total organic acids,total amino acids and soluble sugars secreted by Pteris vittata L.roots increased significantly with the increase of antimony stress concentration,and compared with the blank control group,the contents of total organic acids,total amino acids and soluble sugars secreted by Pteris vittata L.roots increased by 6.04%～101.41%,13.83%～22.82% and 23.85%～254.11%,respectively.The components of organic acids and amino acids were detected,six kinds of organic acids such as oxalic acid,formic acid,lactic acid,acetic acid,citric acid and malic acid and seventeen amino acids such as aspartic acid,threonine,serine,glutamic acid,proline,glycine,alanine,cystine,valine,methionine,isoleucine,leucine,tyrosine,phenylalanine,lysine,histidine and arginine were found.The composition of organic acids and amino acids did not change,and antimony stress mainly affected the secretion of each component.(3)Through the experiment of the effect of exogenous root exudates on the physiological response of Pteris vittata L.,it was found that the addition of exogenous glutamic acid,tyrosine,malic acid and citric acid enhanced the root activity of Pteris vittata L.by 15.61%～30.07%,17.13%～73.46%,53.67%～109.62% and52.97%～132.45%,respectively.At the same time,the activities of antioxidant enzymes such as Superoxide Dismutase(SOD),Peroxidase(POD)and Catalase(CAT)in roots,stems and leaves were increased,the Malondialdehyde(MDA)content in roots,stems and leaves was decreased,and the membrane lipid peroxidation induced by antimony stress was reduced,so as to alleviate the damage of antimony to Pteris vittata L.cells and enhance the tolerance of Pteris vittata L.to antimony.Among them,the effect of malic acid and citric acid was stronger than that of glutamic acid and tyrosine,and the treatment of medium and high concentration was better than that of low concentration.(4)Exogenous glutamic acid,tyrosine,malic acid and citric acid all increased the content of antimony in the roots,stems and leaves of Pteris vittata L.,and promoted the accumulation and transport of antimony in Pteris vittata L..The extraction experiment of antimony binding form in Pteris vittata L.showed that the addition of glutamic acid,tyrosine,malic acid and citric acid increased the proportion of residual antimony in root,stem and leaf cells.Malic acid and citric acid also increased the proportion of transferable Water-soluble antimony in cytoplasm and vacuoles of stem cells.The results showed that exogenous glutamic acid,tyrosine,malic acid and citric acid could enhance the detoxification ability of antimony and increase the migration ability of stem cells to antimony by promoting the transformation of antimony in root,stem and leaf cells to the residue with the lowest activity to promote the absorption and enrichment of antimony by Pteris vittata L..Among them,the promoting effect of low concentration of glutamic acid and tyrosine,high concentration of malic acid and citric acid was stronger.(5)The addition of exogenous glutamic acid,tyrosine,malic acid and citric acid decreased the soil pH value in the following order: citric acid > malic acid > glutamic acid > tyrosine.At the same time,the content of weak acid extracted antimony in soil increased significantly,while the content of residual antimony decreased significantly.Glutamic acid,tyrosine,malic acid and citric acid can improve the bioavailability of antimony in soil and promote the absorption of antimony by Pteris vittata L.by reducing soil pH value and increasing weak acid-extracted antimony in soil. |
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