Studies On The Copper Tolerant Mechanism And Copper Tailing Phytoremediation Of Four Leguminous Plants

1. By applying different levels of three kinds of organic acids, citric acid (Tc),acetic acid (AC) and ethylene diamine tetraacetic acid (EDTA) in the Cu tailings tostudy the seed germination and tolerant of four leguminous plants (Melilotus officinalis(Linn.) Pall, Vigna radiata (Linn.) Wilczek, Vicia faba Linn and Pisum sativum Linn) bypot culture. The results show that seed germination potentials and germination rates offour leguminous plants were lower than control and the seed germination vigors wereseriously inhibited under the high concentration of AC and EDTA. Especially under2mmol/kg EDTA treatment, the germination potential of M. officinalis, V. radiata and P.sativum were decreased66.8%,26.7%and52.6%and the germination rate werereduced39.2%,18.3%and57.5%. The seed germination potential and germination rateof four plants were enhanced by the application of Tc and low concentration of AC.Low concentration of AC promoted M. officinalis and P. sativum vigor index, while, Tconly promoted the vigor index of M. officinalis. The germination indexes of four plantsunder EDTA and high concentrations of AC treatment were lower than that of thecontrol. The tolerance index (IT) of M. officinalis, V. faba and P. sativum under the1mmol/kg AC treatment were increased3.5%,15.3%and14%more than those ofcontrol. ITs of four species under the2mmol/kg EDTA treatment were reducedsignificantly. The changes of plant leaf length, root length, root number and dry weighthave similar trends with IT. The results indicated that AC and Tc play more importantrole in M. officinalis than other three plants and the seed germination rate of V. radiatawas higher than the other three species.2. Effects of different proportion of the Cu tailings and garden soil on thephysiological responses of M. officinalis and V. radiata seedling were studied by potculture. The results show that the chlorophyll contents of two species decreasedgradually as the increment of Cu tailing. The Chla and Chlb contents of M. officinalisunder the3/4Cu tailings treatment were reduced36%and31%that of the control. TheChla, Chlb and Cxc contents of V. radiata under the Cu tailings treatment decreased58.7%,54.7%and55%, respectively, compared with that of the control. The SODactivity in the aboveground part of M. officinalis under the3/4copper tailings and thepure copper tailings increased26.3%and22.3%, respectively, more than that of thecontrol. SOD activities in the aboveground part of V. radiata were dropped significantlycompared with control, while, in the underground part under Cu tailings treatment considerably increased. POD activity in aboveground part of M. officinalis increasesignificantly under1/4Cu tailings treatment, were91.2%higher than that of the control,while, the POD activity of V. radiata were lower than the control, except1/2tailingtreatment. The relative conductivity values of the two species were lower than thecontrol. The contents of MDA, proline and ascorbic acid in the seedlings increased ordecreased not significantly compared with the controls. The results indicated that twospecies had the ability to remediating copper tailing environment and M. officinalis wasmore tolerant to Cu tailings environment than V. radiata was.3. The effects of organic acids on the seedling physiological indexes of M.officinalis and V. radiata growing in the copper tailing were studied by pot culture. Theresults show that chlorophyll contents of two species declined as the level increase ofthree kinds of organic acids and all the seedlings of V. radiata under the addition ofEDTA died. The relative conductivity of above-and underground part of M. officinalisunder the treatment of EDTA were14.39times and1.83times, respectively, of thecontrol. The relative conductivity of V. radiata treated with Tc and AC were notsignificantly compared with control. SOD and POD activities in aboveground part of M.officinalis under the0.5mmol/kg AC treatment increased31.2%and31%, respectively,more than that of control. However, POD activity of M. officinalis under2mmol/kgEDTA treatment significantly reduced. POD, SOD activities of M. officinalis werehigher than those of V. radiata under the treatments of Tc and AC. The MDA contentsaboveground part of M. officinalis under the0.5mmol/kg TC treatment was20.2%morethan control and in the underground part treated with lower level of AC decreasedsignificantly. MDA contents in underground part of V. radiata under the treatment of2mmol/kg Tc decreased to36.4%of the control. Pro contents of M. officinalis under2mmol/kg EDTA treatment significantly increased. Results indicated that differentconcentrations of Tc and AC can improve the tolerance of both species to Cu tailing,while, V. radiata was unadaptable to the interaction between EDTA and Cu stress.4. The effect of the three kinds of organic acids on the seedling growth and metalsaccumulation of M. officinalis and V. Radiata growing in Cu tailing were studied by potculture. The results show that the aboveground part dry weight of M. officinalis underthe2mmol/kg Tc and2mmol/kg AC treatment significantly increased34.4%and29%,respectively, more than that of control. However, the dry weight of M. officinalis underhigh concentration of EDTA treatment dropped significantly. The dry weights of V.radiata under AC and Tc treatments were not significant changed and tolerance index decrease was not significant. A high concentration of EDTA inhibits the growth of M.officinalis and led to the deaths of V radiata. The highest value of Cu content inaboveground part of M. officinalis was found265.167μg/g under the treatment of2mmol/kg EDTA and underground part reached871.111μg/g under the treatment of2mmol/kg Tc. Cu contents in underground part of V. radiata were promoted by thetreatments of AC and Tc. Cu, Cd, Zn translocation and Cu, Cd, Zn absorption of M.officinalis were promoted by the organic acids, but the uptake of Ca was inhibited. Theabsorption of Cu and translocation of Cu, Cd, Ca of V. radiata were enhanced, while,the absorption of Cd, Zn, Ca was inhibited. The results indicated that all the organicacids could improve heavy metals accumulation of M. officinalis and to V. Radiata, therole was not significantly.