Relationships Of Abusular Mycorrhizal Fungi And Plant Roots To Uptake Cobalt In Cobalt Contaminated Soil

Cobalt, as a radioactive element, is becoming a big threat for the environment of human being because it contaminates the soil and pollutes the eco-system. Phytoremediation is an economic, convenient and environmental friendly repairing technology, and the arbuscular mycorrhizal fungi(AMF) has a potential to improve the efficiency of phytoremediation. Using the Tomato and Sunflower as material, the author have studied the influence of AMF on 4 species, including Glomus mosseae, Glomus geosporum, Glomus versiforme, Glomus diaphanum and their combination. At the same time, the author have focused on the growth, Cobalt absorption, transfer and enrichment capacity of each single and combination sample in different Cobalt contaminated soil. It provides the theoretical basis and technical methods to improve the efficiency of phytoremediation. The results show as follows:(1) In different concentrations of Cobalt contaminated soil, according to the AMF parasites by colonizing and depending, it indicates that AMF and plant could form stable mycorrhiza under the pressure of Cobalt. With increasing Cobalt concentration, the plant colonization rate has barely changed, the trend of dependence is increased first and then decreased. The rule of the plant colonization rate and dependence shows as follow: mixed inoculation > single inoculation > natural inoculation, the colonization rate of Tomato and Sunflower is 30%-45%, 30%-40%, respectively. Meanwhile, the colonization rate and dependence reached the maximum when the inoculation is Glomus mosseae and Glomus versiforme.(2) In the 20 mg/kg mild Cobalt contaminated soil, for the plant growth and effect on repairing, it indicates that AMF could promote the growth of plants. Here the promotion effects of mycorrhiza can show as: ① mixed bacteria > single strain. When Tomato and Sunflower inoculated with Glomus mosseae and Glomus versiforme, per plant of dry weight both reached the peak value, 9.90 g and 11.87 g, and which are 2.63, 2.55 times than that of the natural inoculation CK1. ②It could improve inoculations’ capacities of the absorption and accumulation of Cobalt. When inoculated with Glomus mosseae and Glomus versiforme, the accumulation of Cobalt for Tomato reaches the maximum 362.68μg, which is 3.23 times than that of the natural inoculation’s. Similarly, the accumulation coefficient is higher than natural inoculation’s significantly. While inoculats with Glomus geosporum and Glomus diaphanum, the accumulation of each Sunflower reached the maximum 140.53μg, which is 3.09 times than the natural inoculation’s, and the accumulation coefficient of per plant is the biggest, which is 1.67 times than that of the natural inoculation. Therefore, the proper combination way of repairing the Cobalt contaminated soil is that Tomato inoculated with Glomus mosseae and Glomus versiforme and Sunflower inoculated with Glomus geosporum and Glomus diaphanum.(3) In the 40 mg/kg moderate Cobalt contaminated soil, for the plant growth and effect on repairing, it indicates that AMF could promote the growth of plants. Here the promotion effects of mycorrhiza can show as: ① mixed bacteria >single strain. When inoculated with Glomus mosseae and Glomus versiforme, Tomato and Sunflower in dry weight per plant reached the peak, which are 7.79 g, 9.71 g, Tomato and Sunflower in dry weight per plant reached the peak value, which are 9.90 g, 11.87 g, respectively, and which are 2.03, 1.75 times than that of the natural inoculation CK1. ② AMF inoculated in Tomato can enhance the adsorption, transport and accumulation of Cobalt, and the transfer coefficient and accumulation coefficient of per plant are higher than that of the natural inoculation. When inoculated with Glomus mosseae and Glomus versiforme, the accumulation of Cobalt for per Tomato is reached the highest 365.21μg, which is 2.14 times than that of the natural inoculation. AMF inoculated in Sunflower can promote the absorption of Cobalt. When inoculated with Glomus mosseae and Glomus versiforme, the accumulation of Cobalt for per Sunflower reached the highest 267.63μg, which is 2.35 times than that of the natural inoculation. Therefore, both Tomato and Sunflower inoculated with Glomus mosseae and Glomus versiforme is the proper combination methods of repairing the modereate Cobalt contaminated soil.(4) In the 60 mg/kg serious Cobalt contaminated soil, for the plant growth and effect on repairing, it indicates that AMF could promote the growth of plants. Here the promotion effects of mycorrhiza can show as : ① mixed bacteria >single strain. When inoculated with Glomus mosseae and Glomus versiforme, Tomato and Sunflower in dry weight per plant reached the peak value, which are 6.74 g, 7.87 g, respectively, and which are 1.48, 1.60 times than that of the natural inoculation CK1. ② AMF inoculated in Tomato and Sunflower can promote the adsorption of Cobalt and accumulation ability.When inoculated with Glomus mosseae and Glomus versiforme, the accumulation of Cobalt for Tomato and Sunflower are reached the highest, which are 436.00μg and 132.09μg respectively, and which are 1.87 and 1.66 times than that of natural inoculation, respectively. Therefore, both Tomato and Sunflower inoculated with Glomus mosseae and Glomus versiforme is the proper combination methods of repairing the serious Cobalt contaminated soil.(5) The effects of AMF inoculated in different Cobalt contaminated soil on the physiological and biochemical characteristics of plant indicated that the plant inoculated with AMF could weaken the toxicity of Cobalt to the membrane permeability and strengthen the membrane’s resistance. With increasing of Cobalt concentration for different Cobalt contaminated soil, the relative conductivity of leaves and Malonaldehyde both increased, the content of Chlorophyll a, b and the activity of Anticatalase, Peroxidase, Superoxide dismutase in leaves had the same trend which is increased first and then decreased. In the same degree of Cobalt contaminated soil, the relative conductivity and the content of Malonaldehyde showed that: mixed bacteria < single strains < control group. On the contrary, the content of Chlorophyll and the activity of Anticatalase, Peroxidase and Superoxide dismutase showed that mixed bacteria >single strains > control group.