Study On The Effect Of Uranium And Associated Heavy Metals On Physiological And Biochemical Characteristics Of Rumex Acetosa

This paper was supported by the key project of national decommissioning of nuclear facilities and radioactive waste management (14ZG6101).Experimental material was Rumex acetosa, which grows better in uranium tailings. Controlled pot experiments were conducted to examine the effect of U and associated heavy metals single or combined stress on growth, physiological and biochemical of Rumex acetosa, and the effect of U and associated heavy metals single on soil microbial community functional diversity of Rumex acetosa. It provided a reference for the phytoremediation of uranium and associated screening and uranium tailings of hyperaccumulators.Main conclusions obtained are as follows:(1) Low concentration U (less than 50μmol/L) and As (less than 25μmol/L) wre not notable affected the germination rate of Rumex seeds(p<0.05), the high concentration of U (more than 100μmol/L) and As (more than 50μmol/L) were significantly inhabited the germination index of Rumex seeds(p<0.05), different concentration of Mn, Hg and Pb were significantly inhibited seed germination index(p<0.05). Under the single heavy metal stress, SOD, POD, CAT and MDA changed regularity. In low concentration of exogenous heavey metal, Rumex can scavenge active oxygen free radicals, resist the harm of heavy metals; when the concentration of U, Mn, Hg, As, Pb were more than 200μmol/L,1000μmol/L,400μmol/L, 100μmol/L,2000μmol/L, the growth was damaged by heavy metal ion. Germination rate negatively was correlated with Mn (r=-0.930**), and negatively correlated with As (r=-0.963**); Germination potential was negative correlated with As (r=-0.986**) and Pb (r=-0.971**); Germination index was negative correlated with As (r=-0.969**)and Mn (r=-0.934**); POD activity positive was correlated with and Pb (r= 0.997**) and Mn (r= 0.951**); MDA content was positively correlated with Mn (r=0.931**) and As (r=0.853*).(2) under the single heavy metal stress, compared with the control, Rumex leaves’s fluorescence values change in O～K point are not obvious.while after point K were showed on promoting low concentration and inhibiting high concentration trend, maximum photochemical efficiency (Fv/Fm) was not significant; Under different Mn, Hg, As Single Stress, photosynthetic performance index (PIABS) showed increased first and then decreased; under U stress, PIABS decreased significantly in the range of 26.5%～38.1%, while under the Pb stress, PIABS change regularity obvious, when Pb concentration was 1200 mg/kg, PIABS significantly reduced 27.9% compared with the control; Under the U, Mn, As, Pb single stress, Pn, Gs increased first then decreased, while under Hg stress, Pn, Gs were basically increasing; with the heavy metal concentration incresing, antioxidant enzymes SOD, POD, CAT activities and MDA content were substantially increased first and then decreased; Under U, Mn, As a single stress, the content of chlorophyll decreased basiclly, in the range of 5.2%～63.3%, while under Hg, Pb single stress, chlorophyll content increased substantially before a downward trend; Rumex acetosa for patience of Mn and Mn enrichment effects are the best, and the content of Mn is always shoot higher than the roots;Mn concentration of 250～2000 mg/kg, the above ground Mn content of 134.6～454.4mg/kg,TF value was 4.677～5.653; U, Hg, As, Pb enrichment of shoots were 2.33～5.44mg/kg,15.99～ 44.82μg/kg,84.54～494.84μg/kg and 9.17～69.28mg/kg.(3) Under the U and associated heavy metals combined stress, Hg and chlorophyll content positively correlated (r=0.658**); SOD activity was negatively correlated with Pb (r=-0.491*), POD activity was positively correlated with As (r=0.528*) and negative correlated with Mn (r=-0.529*), MDA content and Pb negative correlation (r=-0.557*); Rumex acetosa aboveground and belowground enrichment of U and U concentrations positively correlated (r=0.710** and 0.880**), aboveground Mn enrichment of a positive correlation (r=0.927**) and Mn concentration, and Pb concentrations negative correlation (r=-0.731**); Hg and Pb enrichment of aboveground treatment concentration positively correlated (r=0.567*), underground enrichment of Hg and Hg, Pb concentrations positively correlated (r=0.782** and 0.651**); Underground enrichment of As and As, Hg concentrations were correlation (r=0.854** and 0.690**); aboveground Pb enrichment of a positive correlation (r=0.827*) and Pb concentrations, and U concentration negatively correlated (r=-0.533*), underground Pb enrichment of a positive correlation with the Pb concentration (r=0.806**).(4) With increasing degree of heavy metal pollution, soil microbial community structure was corresponding changed the average absorbance values (AWCD) soil microbial communities and community Shannon index (H), Simpson index (D), richness (S) were significantly lower than the control soil, and the higher the concentration of heavy metals in, the more obvious differences, when the microbial culture to 192h, the decline was 1.7%～61.7%,1.6%～21.8%, from 1.1% to 6.3%,from 0 to 69.6%, It indicated that heavy metal pollution lead to a decline of soil microbial community functional diversity, reducing the ability of microorganisms using a single carbon substrate.