| Coastal wetlands are one of the important ecosystems of the coastal estuary,human activities threaten coastal wetlands from heavy metal pollution.As a safe,effective and environmental friendly soil remediation technology,phytoremediation can be applied to the treatment of heavy metal pollution in wetlands,the utilization of rhizo sphere bacteria is an important factor in promoting plant growth and improving the level of phytoremediation.The purpose of this experiment is to screen out Cd-resistant bacteria to test its growth-promoting ability,and to study the role of strains in regulating the growth of mangrove plants and affecting the absorption and transport of heavy metals in wetland sediments,provide methods and theoretical basis for alleviating heavy metal pollution in wetland ecosystems and achieving good phytoremediation.1.In this paper,nine cadmium-tolerant bacteria were isolated from Fujian Hanjiangkou National Mangrove Nature Reserve,which were Enterobacter sp,Bacillus sp and Pseudomonas sp.The strain Pseudomonas sp.C1 had the strongest Cd tolerance,followed by Pseudomonas sp.2-2.In order to study the growth-promoting properties of isolated strains,this experiment focused on the ability of IAA and siderophore secretion of bacteria.It was found that all 9 strains produced indoleacetic acid(IAA),of which 5 strains of Enterobacter produced the most prominent IAA.Among them,Enterobacter sp.C10 had the ability to secrete siderophore.Based on the study of Cd-resistant and growth-promoting properties of strains,three strains of Pseudomonas sp.C1,Pseudomonas sp.2-2 and Enterobacter sp.C10 were selected for indoor simulated regression experiments to further verify the effect of test bacteria on mangrove plants.2.The inoculation of three plant-promoting bacteria promoted the elongation of Avicennia marina roots.When Cd was applied at a concentration of 5 mg/kg,Enterobacter sp.C10 was inoculated to significantly increase the roots of Avicennia marina.The results showed that the tested strains promoted the growth of Avicennia marina roots.The growth-promoting effect of Enterobacter sp.C10 was particularly significant.3.The inoculation of three plant-promoting bacteria promoted the increase of biomass of Avicennia marina,and the growth-promoting ability of three kinds of bacteria to Avicennia marina was:Enterobacter sp.C10>Pseudomonas sp.2-2>Pseudomonas sp.C1.Under Cd stress,the toxicity of Cd to Avicennia marina was firstly reflected in the roots of plants,and the biomass of Avicennia marina was inhibited,but the application of growth-promoting bacteria alleviated the toxic effect of Cd on plant roots and increased root biomass.The biomass of stems and leaves has also increased,in particular,the growth-promoting effect of Enterobacter sp.C10 is most significant.The increase in total biomass is not only a manifestation of the growth-promoting effect of the growth-promoting bacteria,but also indicates that the plant has a greater ability to absorb heavy metals.4.Heavy metals were mainly enriched in the roots of Avicennia marina by measuring the content of heay metals Cd and Fe in plant.Inoculation with the strains Pseudomonas sp.C1 and Pseudomonas sp.2-2 increased the enrichment of Cd by Avicennia marina.Under the treatment of Cd5,the content of Cd enriched in the roots and stems of Avicennia marina inoculated with Enterobacter sp.C10 was significantly decreased,while the content of Cd enriched in leaves was significantly increased.The inoculation of Enterobacter sp.C10 reduced the absorption of heavy metal Cd by Aivicennia marina and increased the transport coefficient of Cd from root to leaf,which effectively alleviated the toxic effect of heavy metal stress on plants5.The inoculation of three plant-promoting bacteria in the experiment reduced the Cd content in the rhizosphere soil of Avicennia marina.At the treatment level of Cd5,the Cd content in the rhizosphere soil of Enterobacter sp.C10 was significantly reduced The experimental results show that these three experimental strains play an important role in promoting the absorption of heavy metals by mangrove plants and strengthening the repair of soil Cd pollution.It has important practical significance in helping plants to repair and control heavy metal pollution in wetland ecosystems. |
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