Fudamentals Of Eupatorium Adenophorum And It's Root-endophtic Fungi In Ecological Reconstruction Of Heavy Metal Mining Area

Anthropic intensively mining and smelting acitivities produce mass mine tailing soils with excessive heavy metals, which destroys and occupies a considerable amount of land for both agriculture and residence and poses detrimental effects on ecosystems with long-time weathering in field. To clean-up of mass mine tailing soils and protect the neighboring environments from the pollutants becomes an urgent problem. In the past decades, increasing evidence demonstrated that to revegetate plants would be one of most effective countermeasure of point pollution resources of mine soils. In the current study, the colonization of both arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) of natural growing plants in the tailing of Pb-Zn mine in Lancang county of Yunnan province were investigated. AMF and DSE colonized the plants in study area were isolated and screened, the taxonomy position and resistance to heavy metal of the isolated strains were studied. Using the AMF and DSE as fungal inoculum, we investigated the colonization effect on Eupatorium adenophorum under Cd stress, the results are as follows:1. AMF and DSE colonization status of natural growing plants in Pb-Zn mine tailings in Munai, Zhutang township, Langcang County of Yunnan province were investigated by the alkaline lysising and acid fuchsin staining method. 19 species of plants had typical AMF colonization which means AMF colonization coverage reached to 79.17% in this area (24 species 19 families, surveyed), four plants could not form arbuscular mycorrhiza (AM) and one plant species could not be identified. Among the 19 plant species typically colonized by AMF, one was found to be intensively colonization, 15 in normal colonization and 3 in lightly colonization. Among all 24 species of natural growing plants, seventeen species (70.83%) of sampled plants were colonized by DSE, and these 17 DSE plant species were co-colonized by AMF simultaneously. Eupatorium adenophorum. As a dominant plant species in the mining area, Eupatorium adenophorum has been generally colonized by AMF and DSE, with the colonization rate of 51.21% and 30.62% respectively.2. Roots and rhizosphere soils of Eupatorium adenophorum as AMF inocula were trap-cultured by maize and clover to isolate AMF in a greenhouse and the dominant morphological AMF species, Glomus mossae and Glomus sp. were screened. One root-associated endophytic fungal strain H84-1 isolated from heavy metal pollution area was targeted, and identified to be Exophiala pisciphila based on its morphological characteristics and molecular phylogenetic analysis. In a pot experiment, Koch's Postulate test,was conducted that E. pisciphila H84-1 were inoculated with maize seedling roots and re-isolated. Koch's Postulate test,confirmed that H84-1 could form typically DSE structures in maize roots without obvious pathological changes. Our results showed that H84-1 had an inherent tolerance to cadmium in-vitro.3. In the greenhouse, pot experiments were conducted to study the effects of single AMF, DSE inoculation and co-inoculation on Eupatorium adenophorum. Our results showed that 1) both AMF and DSE strains could colonize the roots of Exophiala pisciphilain all test Cd concentrations and their colonization intensity increased with the increasing Cd supply. 2) The growth of Exophiala pisciphila inoculated and non-inoculated with H84-1 was inhibited by increasing Cd pollution. However, compared with non-inoculated groups, inoculation with H84-1 could increase the the shoot and root biomass of Eupatorium adenophorum. 3) Whether inoculated with fungi or not, Cd was mainly accumulated in roots of Exophiala pisciphila. The accumulation of Cd increased as the increasing Cd in medium. Compared with the control, AMF and DSE inoculation increased the absorption of Cd by Exophiala pisciphila. 4) Colonization of AMF/DSE could significantly enhance the Cd enrichment ability of Exophiala pisciphila, and the enrichment coefficient of the single DSE inoculation group was twice as the control group. 5) The inoculation of AMF/DSE could enhance the SOD activities to alleviate the oxidative damage and strengthen the resistance of Eupatorium adenophorum to Cd.Our study showed that the heavy metal mining area have been severely polluted by axcessive heavy metals. In Munai mining area, most plant species including the most dominant plant species Eupatorium adenophorum were colonized by AMF and DSE. Eupatorium adenophorum has higher resistance to heavy metals and the colonization of AMF and DSE also influence the Cd transition and accumulation between plant root and shoot and strengthened their resistance to heavy metals. These results suggested that screening for AMF and DSE strains, optimizing the efficient associations between AMF/DSE and Eupatorium adenophorum, may have a great potential application in the bioremediation of heavy metal contaminated soils.