| Recently,due to the development of industry and human activities,the arid and semi-arid areas with natural saline soil have been subjected to the stress of heavy metal pollution.Phytoremediation technology has the advantages of economic and environmental protection and is a common technology for remediation of heavy metal contaminated saline soil.However,plants have problems of slow growth and low repair efficiency under various stresses.Arbuscular Mycorrhizal(AM)fungi can enhance the tolerance of plants to heavy metals and salt stress,which has potential for improving the efficiency of phytoremediation.However,studies on the remediation of heavy metal contaminated saline soil with AM fungi have not been reported.In this study,natural saline soil(total salt 2.238 g·kg-1)was collected,and cadmium(Cd,2.00 mg·kg-1)and lead(Pb,100.00 mg·kg-1)were added to simulate the combined pollution of heavy metals in saline soil.To investigate the effects of heavy metals and AM fungi(Funeliformis mosseae)on the growth,nutrient elements,absorption and transport of stress ions(Cd,Pb and Na)and rhizosphere soil bacterial community of Astragalus adsurgens.The results showed that:(1)AM fungi colonized the root of Astragalus adsurgens and formed a good symbiotic relationship,and the average infection rate ranged from 15.83%?23.69%.Whether or not AM fungi were inoculated,the addition of single or combined cadmium and lead significantly inhibited the plant growth.AM fungi markedly increased the shoot and root biomass by 536.10%?970.22%and 272.01%?382.19%in all treatment groups compared with those without inoculation.(2)Whether or not AM fungi were inoculated,the addition of Pb decreased the concentration of Cd in shoots and roots of Astragalus adsurgens.But the addition of Cd increased the concentration of Pb in shoots of Astragalus adsurgens.Inoculation with AM fungi significantly reduced Cd and Pb concentrations and transport factors in shoots and roots of Astragalus adsurgens in all treatment groups compared with non-inoculation.In the group without AM fungi treatment,the addition of Pb and combined treatment significantly reduced the concentration of Na in shoots and roots of Astragalus adsurgens.In the group inoculated with AM fungi,the addition of Pb alone and combined treatment significantly increased the concentration of Na in the roots of Astragalus adsurgens.Inoculation with AM fungi significantly reduced Na transport factors compared with non-inoculation.(3)Proteobacteria(26%?39%)and Firmicutes(16%?38%)were the most abundant bacterial groups in the rhizosphere soil of Astragalus adsurgens with or without AM fungi.LEf Se analysis showed that heavy metal-resistant bacteria(Pseudomonas,Lysobacter and Paenibacillus)were significantly enriched by single or combined cadmium and lead treatments in the treatment group without AM fungi inoculation.In the AM fungal inoculated group,single or combined cadmium and lead treatment significantly enriched resistant heavy metal bacteria(Steroidobacter,Massilia and Peredibacterthat)can promote plant growth.AM fungi significantly enriched more growth-promoting bacteria(Archangium,Pedomicrobium and Rhodobacter)in all treatment groups compared with non-inoculation.(4)In the treatment group without AM fungi inoculation,single or combined cadmium and lead treatment reduced the community richness(Chao index),diversity(Shannon index)and bacterial interactions in the rhizosphere.In the AM fungi inoculated group,single or combined cadmium and lead treatments had no significant negative effect on the richness,diversity and interaction of rhizosphere bacterial community.Compared with no inoculation,AM fungi significantly increased the richness and diversity of rhizosphere bacterial community in all treatment groups,and strengthened the interaction relationship between bacteria.And the increased negative correlation of AM fungi indicates a healthier and more stable ecological environment.Research results showed that AM fungi can promote the absorption of nutrients,adjust plant uptake of heavy metals and salt ions of transport,improve the richness and diversity of rhizosphere bacterial communities and promote the enrichment of beneficial bacteria rhizosphere,strengthen role relationship between bacteria resistance of plants to heavy metals and salt stress.Finally,the plant growth was promoted and the efficiency of phytoremediation was improved.This study provided theoretical foundation and data support for repairing saline soil contaminated by heavy metals. |
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