The Resource And Lead-Resistance Of Arbuscular Mycorrhizal Fungi At Lead And Zinc Diggings In The Qinling Mountains

The arbuscular mycorrhizal fungi in the rhizosphere of 4 plants at lead and zinc dinggings in Qinling mountains at Feng County in Shaanxi Province were studied. The effect of lead on physiology and biochemistry of maize was studied by inoculated with two indigenous arbuscular mycorrhizal (AM) inoculants M1 and M2, that M1 inoculant isolated from high Pb concentration soil, while M2 inoculant from low Pb concentration soil. The distribution of lead in the mycorrhiza was also studied by transmission electron microscope(TEM) to reveal the mechanism of AMF lead-resistance from cellular level.1. The resource of AMF at lead and zinc dinggings in Qinling mountains and the effect of soil factors12 species arbuscular mycorrhizal fungi were identified from the rhizosphere of Anemone hupehensis V. Lem., Juglans regia L., Zea mays L., Diospyros kaki Lf. at diggings contaminated by lead and zinc in the Qinling Mountains, in Feng County. They were G. aggregatum, G. caledonium, G. constrictum, G. coronatum, G. dimorphicum, G. formosanum, G. geosporum, G. intraradices, G. monosporum, G. mosseae, G. pansihalos, G. versiforme and all were Glomus. G. constrictum was the dominant species in this area. G. constrictum, G. coronatum, G. caledonium and G. aggregatum were more resistant to heavy metals, while G. geosporum, G. formosanum, G. versiforme and G. dimorphicum were less resistant to heavy metals. Correlation analysis indicated that lower Pb, Zn, extractable P and pH advanced AMF species richness, however, higher Pb, Zn, extractable P and pH had negative effects on the AMF species richness. AMF species richness had negative correlation with higer Pb(P<0.01) and Zn(P<0.05) concentrations. Path analysis revealed that Pb was the main factor that affected AMF species richness in this area. Both its direct and indirect effects were big. pH, extractable P and Zn mainly affected AMF species richness through the indirect effect of Pb.2. The effect of AMF on maize's physiological and biochemical indicator of lead-resistanceThe effect of lead stress and inoculation with two indigenous arbuscular mycorrhizal (AM) inoculants on root colonization and plant growth was studied in maize(Zea mays L.) by pot experiment. The M1 inoculant isolated from high Pb concentration soil(1 216.01μg/g), while M2 inoculant from low Pb concentration soil(57.81μg/g). Arbuscular mycorrhizal colonizations were reduced from 98.10% to 48.53% by lead stress. In comparison with CK, Height, base diameter, overground and belowground dry matter yields, Chlorophyll and Superoxi dedismutase (SOD) content were significantly higher, proline and malondialdehyde (MDA) content were significantly lower. Overground and belowground dry matter yields inoculated with M1 were significantly higher than that of M2, and overground Pb content were significantly lowerer than that of M2. At high Pb concentrations (200~1 000μg/g), root colonization, height, Chlorophyll and SOD content with M1 significantly higher than M2, while proline and MDA significantly lower than M2. These results indicated that AMF inoculant can enhance lead-resistance of maize, especially at high Pb concentration stress, the effects of M1 were better than M2.3. The location of lead in the arbuscular mycorrhiza by TEMAMF colonized the parenchyma cells located in the cortex. AMF can alleviate the toxicity of lead through shrinkage of protoplasm away from the wall of hyphae. From the TEM images, it was observed that hyphae and vesicles have been compartmentation. Pb can locate on hyphe wall, hyphe inner-compartments, hyphe inner-compartments membrane, inner-compartments of vesicles and inner-compartments membrane of vesicles. Immobilization of the lead in arbuscular mycorrhiza can reduce the translocation of lead from soil to root, to alleviate the potential toxicity of lead.