Mechanism Of Arbuscular Mycorrhizal Fungi And Chelating Agents In Facilitating The Halophyte Remediation Of Heavy Metal Contaminated Saline Soils

In recent years,with the acceleration of urbanization,industrial development,and excessive use of agricultural chemicals,many arid,semi-arid areas and coastal,estuary tidal flat soils of the world,including China have been"Doubly"affected by salinization and heavy metal,heavy metal contaminated saline soil has become a worldwide environmental problem.At present,the use of halophytes to repair heavy metal contaminated saline soils has good economic and environmental effects and application prospects,but there are key problems of great toxic effects on plant growth and low repair efficiency.However,the role and mechanism of arbuscular mycorrhizal fungi and chelating agents joint facilitating the halophyte remediation of heavy metal contaminated saline soils has not been reported.The research was conducted with greenhouse pot experiment,simulating Cadmium contaminated soil?5 mg Cd·kg^-11 dry soil,Cd5S0?and Cadmium contaminated sodium chloride saline soils(2.5 g NaCl·kg^-1,Cd5S2.5).To explore the effect of inoculation of the Funneliformis mosseae?Fm?and chelating agents(5 mmol·kg^-1EDTA,10 mmol·kg^-11 NTA,0.25 g·kg^-1HA)on Suaeda salsa growth index,transcriptomics of shoots,the bacterial community structure of the rhizosphere,the physicochemical properties of the soil and the influence of enzyme activity.Revealing the effects and mechanisms of AM fungi and chelating agents joint facilitating the halophyte remediation heavy metal contaminated saline soils.Research indicated that:?1?F.mosseae established a symbiotic relationship with Suaeda salsa root system successfully.The mycorrhizal inoculation rate was between11.34%²2.33%.The addition of three chelating agents reduced the mycorrhizal inoculation rate of the Cd5S0 treatments by 37.30%⁴9.22%.Cd5S0 treatments,Compared with the non-inoculation treatments,the shoots biomass of Suaeda salsa was significantly increased by 3.87 times;Compared with EDTA treatment,shoots biomass significantly decreased by 61.90%of F.mosseae combined with EDTA treatment.Cd5S2.5 treatments,Compared with HA treatment,shoots and roots biomass significantly decreased by 81.80%and 57.28%of F.mosseae combined with HA treatment;Compared with NTA treatment,shoots and roots biomass significantly increased by 287.50%and 433.33%of F.mosseae combined with NTA treatment,the absorption of N and P by the shoots significantly increased by 183.56%and 291.82%,the content of soil alkaline phosphatase increased significantly by 95.38%,and the absorption of Na⁺by shoots and roots increased significantly 128.99%and 842.86%,Cd²⁺absorption increased significantly by 236.62%and 36.91 times,respectively.?2?The analysis of the diversity of the bacterial community in the rhizosphere of Suaeda salsa showed that Proteobacteria,Firmicutes,Actinobacteria and Bacteroidetes are the dominant bacterial groups.It accounts for 74%⁸8.6%of the total bacterial community.Compared with NTA treatment,NTA and F.mosseae joined increasing the average relative abundance of common plant growth promoting rhizobacteria?PGPR?Brevundimonas,Bacillus,and Arthrobacter.In addition,the average relative abundance of Aminobacter,which can degrade NTA chelating agent,also increased significantly.Soil pH and available K are the main driving factors of bacterial community structure changes.?3?The results of transcriptomics sequencing analysis of shoots of Suaeda salsa showed that:There were 585 differentially expressed genes,293 of which were up-regulated genes and 292 of which were down-regulated genes.According to the enrichment analysis of GO and KEGG,the genes of antioxidant stress,hormone signal regulation and stress tolerance of plant MAPK signaling pathway?Pathway ID:map04016?and plant signal transduction pathway?Pathway ID:map04075?changed significantly to cope with NaCl and Cd stress.The results showed that only the effect of NTA and F.mosseae joined facilitating Suaeda salsa repairing Cd-contaminated sodium chloride saline soils is better than that of chelating agent alone.The combination of the NTA and F.mosseae can improve the absorption of mineral nutrients significantly,increase the richness of PGPR,and induce the gene expression of antioxidant enzymes,salt and heavy metal resistant proteins in shoots of Suaeda salsa to alleviate the toxicity of Cd or NaCl,promote the growth of Suaeda salsa and the accumulation of Na⁺and Cd²⁺.The results can provide basic data and theoretical basis for the study of facilitating measures for halophyte remediation of heavy metal contaminated saline soils.