The Tolerance Mechanisms Of Cu、Cd、Pb And Zn By Eucalyptus In Mine Contaminated Soil

The actual mine contaminated soil was adopt for pot experiment to determine the tolerance mechanisms of Cu, Cd, Pb and Zn for Eucalyptus in actual mine containmented soil, and study the effect of the metal tolerance mechanisms of Eucalyptus while arbuscular mycorrhizal fungi inoculated. According to the sample survey, samples were divided as slightly, moderately and heavily polluted sites, every leval have two sites for pot experiments. Pot experiment of inoculation and non-inoculation AM fungi after sterilization were also studied. Each treatment was repeated for three times, the plants were harvested at 16 week after transplantation and then determined the biomass of shoot and root in Eucalyptus, the content and the subcellular distribution of Cu, Cd, Pb and Zn in roots, stems and leaves, the chemical forms of Cu, Cd, Pb and Zn in Eucalyptus roots were also studied.The results show that:(1) When heavily polluted, the accumulation of Cu, Cd, Pb and Zn in Eucalyptus decreased. (2) When heavily polluted, Cu, Cd, Pb and Zn in Eucalyptus mainly store in roots, and compared to the lightly polluted sites, the transfer coefficients by Cu, Cd, Pb and Zn reduced. (3) Cu, Cd, Pb and Zn were mainly found in the cell wall of Eucalyptus, when heavily polluted, the proportions of Cu and Cd in the soluble fraction increased, and the proportion of Pb in cell wall increasesed at Eucalyptus roots. (4) Cd and Pb were mainly extracted by sodium chloride and hydrochloric acid.The proportions of Cu and Zn in the respective extractable at Eucalyptus roots were relatively uniform, While heavly polluted, the fraction of Cu, Cd, Pb and Zn in ethanol and deionized water extractable at Eucalyptus roots reduced. In conclusion, absorption Limitation in the roots, retention in roots, binding in cell wall, compartmentalization in the soluble fraction and reduce the activity of heavy metal are the mechanisms of Eucalyptus tolerance of Cu, Cd, Pb and Zn.While Inoculation with Glomus elunicatum the results show that:(1) Inoculation with AM fungi increased dry biomass of Eucalyptus under heavily metal polluted. (2) Compare to non-inoculation, when serious polluted, inoculation with AM fungi could increased the distribution of heavy metals in the roots of Eucalyptus, and also reduced the transport of Cu, Cd, Pb and Zn, the effect of the retention of roots was strengthen. (3) At the same time, inoculated with AM fungi increased the ratio of soluble fraction for Cu. Cd, Pb and Zn in Eucalyptus roots while serious polluted, the ratio of cell wall for Pb and Zn increased slightly. Also, the ratio of nucleus chloroplasts and mitochondria fractions relative decreased or remained stable. (4) While heavily polluted, the ratio of ethanol and deionized water extractable redused when inoculated with AM fungi at Eucalyptus roots, and the proportion of low activity forms increased. In conclusion, Inoculation with AM fungicould strengthen one or a few tolerance mechanisms by Eucalyptus.