Effects Of Uranium Pollution On Physiological,biochemical And Rhizosphere Soil Physical And Chemical Properties Of Male And Female Poplars

With the rapid development of society and economy,the global demand for new and clean energy such as nuclear energy has increased sharply year by year.Radionuclide uranium,as the most widely used nuclear energy raw material,has caused more and more serious environmental pollution.As a sustainable green remediation technology for the treatment of uranium contaminated soil and water,phytoremediation has great potential in application prospect.However,there is still a lack of research on the remediation of uranium contaminated soil by woody plants.Therefore,under the condition of soil uranium pollution（50 mg/kg）,this paper studied the changes of physiological and biochemical level and rhizosphere soil physical and chemical properties of male and female poplar,so as to explore the mechanism and feasibility of using male and female poplar to repair uranium contaminated soil.The main research results show that:1.In the uranium treatment group,the net photosynthetic rate（A）,the contents of chlorophyll a and chlorophyll b,PSI relative electron transfer rate ETR（Ⅰ）,PSI photochemical quantum yield Y（Ⅰ）and PSII photochemical quantum yield Y（Ⅱ）of male and female poplar plants decreased compared with control group,and the contents of hydrogen peroxide（H₂O₂）and malondialdehyde（MDA）increased,indicating that the photosynthesis of plants was inhibited and the effect of oxidative stress was intensified.Compared with the male and female poplar plants planted separately,the net photosynthetic rate（A）,intercellular carbon dioxide concentration（Ci）,transpiration rate（E）,stomatal conductance（Gs）,PSII non photochemical quenching ability Y（NPQ）and the contents of POD,SOD,soluble sugar,soluble protein,chlorophyll a and chlorophyll b of the male and female poplar plants planted together increased,Y（NO）decreased,and the content of H₂O₂ was significantly lower than that of the male plants planted separately（P<0.05）.It showed that the combination of male and female poplar plants was conducive to improve the photosynthesis of plants,reduce the production of H₂O₂and MDA,and promote the production of antioxidant protective enzymes such as POD and SOD and osmoregulation substances,so as to alleviate the peroxidation damage of plants under uranium stress and strengthen the defense ability of plants against uranium stress.The intercellular carbon dioxide concentration（Ci）,transpiration rate（E）and stomatal conductance（Gs）of male plants were higher than those of female plants,while the proline（Pro）and soluble sugar contents of male plants were lower than those of female plants,indicating that male plants had stronger photosynthetic ability under uranium stress,and male plants were more defensive than female plants.2.The dry weights of roots,stems and leaves of the male and female poplar plants planted together in the uranium treatment group were less than those planted together in the control group,indicating that uranium stress inhibited the growth of plants.The dry weights of roots,stems and leaves of male plants were slightly larger than that of female plants,indicating that male plants had stronger tolerance to uranium stress than female plants.The enrichment characteristics of uranium in each part of male and female poplar plants were basically the same,and the order of uranium enrichment content was root>leaf>stem,and the stem leaf transport coefficient was significantly greater than the root stem transport coefficient.Compared with the male and female poplar plants planted separately,the uranium content in the stem and leaf of the male and female poplar plants planted together increased by 123.12%and 774.59%respectively,and the root stem and stem leaf transport coefficients increased by 476.47%and 235.27%respectively,indicating that under uranium stress,the combined cultivation of male and female plants was more conducive to improve the enrichment and transport capacity of uranium.3.In the uranium treatment group,the p H and electrical conductivity（EC）of rhizosphere soil of male and female poplars decreased,and the contents of acid phosphatase（ACP）,alkaline phosphatase（AKP）,urease and sucrase increased.The combined cultivation of male and female plants increased the p H and EC of rhizosphere soil.The contents of ACP and AKP in rhizosphere soil of male and female poplar plants planted together in control and uranium treatment group were lower than those of male and female poplar separately planted.The contents of urease and sucrase in rhizosphere soil of male and female poplar planted together in control group were significantly higher than those of male and female poplar separately planted（P<0.05）,indicating that the combined cultivation of male and female poplar made the inhibition effect of ACP and AKP in rhizosphere soil and the activation effect of urease and sucrase in rhizosphere soil.Compared with control group,the proportion of rhizosphere soil organic matter and available phosphorus content of male and female poplar plants in uranium treatment group decreased,and the contents of soil available nitrogen and available potassium increased,indicating that plants could effectively promote the decomposition of soil organic matter and stimulate or inhibit the transformation activity of soil nutrition through root secretion.In the control and uranium treatment group,the contents of available nitrogen,phosphorus and potassium in rhizosphere soil of male and female poplar plants planted together were higher than those of male and female poplar plants planted separately,indicating that the combined cultivation of male and female poplar plants could better stimulate the accumulation of more nutrients in plant rhizosphere and was conducive to plant growth.In conclusion,uranium stress would cause peroxidation damage and osmotic stress to male and female poplar plants,inhibit their photosynthetic ability,reduce the content of p H,EC,organic matter and available phosphorus in rhizosphere soil,and then affect the normal growth of plants.The combined cultivation of male and female poplars could effectively improve the photosynthesis of plants,enhance the ability of antioxidant and osmotic regulation,maintain the normal growth of plants,and promote the enrichment and transport of uranium.Male plants showed stronger uranium tolerance than female plants.