Accumulation And Response Mechanism Of Three Aquatic Plants To Uranium Stress In Hydroponic Condition

With the developing of nuclear industry and over exploitation of natural uranium resources, more uranium polluted water are produced and become a great serious threat to the environmental safety. Therefore the issue caused more concerns on the available remediation of uranium polluted water. The physio-biochemical responses and accumulation characteristics of Pistia stratiotes L., Eichhornia crassipes and Lemna minor L. to uranium stress were studied with solution culture experiments by different uranium treatments including different concentration of uranium and applied with or not with effective microorganisms and phosphates. The research results are as followed:(1) The antioxidant enzyme systems including superoxide dismutase(SOD), catalase(CAT) and peroxidase(POD) of P. stratiotes L., E. crassipes and L. minor L. were increased significantly except the SOD of L. minor L.. In addition, the CAT and POD activites of P. stratiotes L. and E. crassipes showed the alternate increasement trends. The three aquatic plants suffered serious oxidative stress at 50 mg·L-1 U, which caused by the contents of MDA and Pro increasing drastically. The chlorophyll contents and biomass of P. stratiotes L.and E. crassipes reached maximum value at 0.05 mg·L-1 U stress, and then decreased significantly with U concentration increased. However, the chlorophyll contents and biomass of L. minor L. were not changed obviously, which indicated its endurance to U stress. From the point of U accumulation, t he root were proved to be the main accumulation part of P. stratiotes L., E. crassipes, in which the highest enrichment reached to 151.01 mg·g-1 DW and 4.92 mg·g-1 DW respectively. Taking into account the maximum accumulation of L. minor L. at 42.45 mg·g-1 DW, the U enrichment abilities of three aquatic plants were as followed the order of P. stratiotes L. > L. minor L. > E. crassipes.(2) With applied effective microorganisms(EM), the CAT, POD and SOD activities of E. crassipes and P. stratiotes L. increased more significantly than that of the control group, the maximum U accumulation contents in root, accumulation factor and transfer actor of P. stratiotes L. increased with 22.6%, 74.0%, 160.0% than that of the control group. The maximum accumulation factor of E. crassipes increased with 172.7% than that of the control group as well as. The results indicated that the EM applied are positive to the resistance, enrichment and transfer ability of E. crassipes and P. stratiotes L. to the U stress. However, the applied EM appeared to be negative to the U resistance and accumulation of L. minor L. with the activities of CAT, POD, SOD decreased, the contents MDA, and Pro increased and especially the chlorophyll contents and biomass decreased drastically. Therefore, our results sug gested the E. crassipes and P. stratiotes L. combined with EM may be the one of helpful way to remediate U polluted water.(3) The phosphate applied improved the antioxidant enzyme activities of P. stratiotes L., E. crassipes and L.minor L. and stimulated the chlorophyll biosynthesis of three acquatic plants. In addition, with the applied phosphate, the maximum U accumulation contents of P. stratiotes L. increased 79.7%, as well as transfer factor of E. crassipes increased 98.5% compared to the control. On the contrary, the U accumulation contents of P. stratiotes L. and L.minor L. decreased 68.1% and 52.6% respectively with the phosphate applied. These results indicated that phosphates applied are positive to the endurance and accumulation of E. crassipes to the U stress, but are somewhat negative to P. stratiotes L. and L. minor L..