Study On Response To Lead And Zinc Of Three Local Legumes Species On Lead-zinc Mining Tailings

Through research soil and plants of lead-zinc tail mining of Huize, andselected tolerant plants through tested heavy metal concent in colonized plants onlead-zinc tail mining and studied germination of seeds under stress of Pb²⁺and Zn²⁺.Used different way to plant three local legumes species, in order to find optimalgrowth plants for revegetation on lead-zinc tail mining, seek best way to plant,providing scientific basis to revegetation and soil bioremediation in lead-zinc tailmining.The results showed that lead-zinc tailings soil was bad to plants grow, becauseheavy metal content was high, but the content of organic matter, N, P, K were low inlead-zinc tailings soil. The heavy metal content have decreased with prolongingaccumulation time, and the heavy metal content of tailings edge is significantly lowerthan the center. There were a lot of natural colonized species on lead-zinc tailings ofHuize, ten species were dominant. The ten species were far way from critical levelsfor hyper accumulator, but could grow under heavy metals stress and have a hightolerance to Pb and Zn, so can be considered as pioneer plants of revegetation inlead-zinc tailings of Huize.Under Pb²⁺or Zn²⁺stress, the seed germination and seedling growth of three plantswere inhibited under concentration of Pb²⁺-Zn²⁺on this paper, and except ViciaCracca, the higher concentration of heavy metal ion was, the stronger inhibition wasexerted on two others. Under double Pb²⁺-Zn²⁺salts, the complicated interactionexisted commonly among the experiment plants. When the concentration of Zn²⁺waslow, the inhibition of Pb²⁺was alleviated by Zn²⁺in Trifolium repens and Medicagosativa. Similarly, when the concentration of Pb²⁺was low, the inhibition of Zn²⁺wasalleviated by Pb²⁺, but the concentration of Pb²⁺or Zn²⁺both were high, the inhibitionon the seed germination and seedling growth were enhanced by each other. The resultalso showed that, the tolerance capability to Pb²⁺/Zn²⁺of Vicia Cracca was thestrongest under the stress of single salt or double salts, the tolerance capability ofTrifolium repens in the second, and Medicago sativa showed the weakest tolerancecapability to Pb²⁺/Zn²⁺.Trifolium repens L. and Vicia Cracca L. are taken as pioneer plants of lead-zinc tailings according to characteristics of the three local legumes speciesduring the growth periods about indexes of the seeding survival, height, biomass,chlorophyll content, SOD （superoxide dismutase） and CAT （catalase） activity, TF75（75percent tailings soil+25percent rural soil） amendment approach is morereasonable for the revegetation of lead-zinc tailings in Lanping based on three locallegumes species growth indexes and feasibility. Water-retaining agent can prolongsurvival time of plants and keep stability of moisture and proline content in plantsunder drought stress. Survival numbers and moisture content of plants leafs decreasewith prolonging drought stress time, and proline content of plants leafs increase withprolonging drought stress time. There was no significant difference of survivalnumbers and moisture and proline content in plants on tailings soil with0.3%and0.4%water-retaining agent, so0.3%water-retaining agent was best dosage in tailingssoil for revegetation of lead-zinc tailings in Lanping.Sequence analysis revealed that among49positive clones in the16S rDNA library,3OTUs （operational taxonomic units） were identified based on the similarity of40%the ARDRA banding profiles at different sampling sites where the nitrogen andPb²⁺/Zn²⁺contents were different. It indicated that the genetic diversity anddistribution of rhizobia may be related with the nitrogen and Pb²⁺/Zn²⁺contents in soil.Sequence analysis revealed that diverse phyla of representative strains in the16SrDNA library belonged to the three phylogenetic branch of Rhizobium sp.,Sinorhizobium sp. and Bradyrhizobium sp. The results suggest that the geneticdiversity of rhizobia isolated from nodules of leguminous plant is very abundant inlead-zinc mining tailing of Lanping, Yunnan. The strains SWFU01, SWFU19,SWFU28, SWFU38, SWFU40, SWFU51, SWFU73can grow under Pb²⁺/Zn²⁺stress.Three local legumes species in pots were watering in strains after mixed culture,physical signs of tested plants shown that rhizobium in favour of plants growth onlead-zinc tailings soil.