The Promoting Effect Of Phosphorus-solubilizing Bacteria On Remediation Of Cadmium-contaminated Saline Soil By Suaeda Salsa

The double contaminated problem of heavy metals and salinization can be caused by natural or human activities is growing seriously in China.The previous studies of our research group have reported that suaeda salsa as halophyte with the potentiality for remediation and accumulation of cadmium-contaminated saline soil.In order to improve efficiency of remediation by Suaeda salsa,the phosphorus solubilizing bacteria-Suaeda salsa combined bioremediation was build,to explore the effect of phosphorus-solubilizing bacteria on plant growth and uptake cadmium in contaminated soil.Root exudates of Susaeda salsa were collected from a sterile hydroponic?with 2%NaCl?culture.Five cadmium-and phosphorus-solubilizing isolates were cultivated using the exudates as a unique carbon source in medium,Their ability of solubilizing P and Cd were studied in Monkina liquid medium with concentration of carbon source was 1g·L^-1.Escherichia grew faster and had stronger cadmium-and phosphorus-solubilizing abilities than the rest of the isolates.Herein,its ability to solubilize P and Cd from Ca₃?PO₄?₂ and CdCO₃,respectively,and its changes of metabolic products in salt stress were studied using a shaking flask experiment.A pot experiment was conducted to study the competitive edge of Escherichia under different nutrient rhizosphere,then,the promoting effect of Escherichia on remediation of cadmium-contaminated saline soil by Suaeda salsa under salt stress was investigated preliminarily.The results showed that:?1?Escherichia produced 80.19,78.79,and 77.54 mg·L^-11 dissolved phosphorus and 17.84,17.30,and 19.73 mg·L^-11 dissolved cadmium,respectively,with the increasing salt concentration treatments in laboratory culture.This shows that an increasing concentration of salt had no effect on P release and promoted Cd release.?2?In laboratory cultivation condition,there was obvious change in the composition of metabolites of Escherichia under the different salt treatments.With the 0.3,6,and 12 g·L^-11 salt treatments,5,10,and 13 kinds of organic acids and 4,8,and 8 kinds of amino acids were released,respectively.The valine content increased significantly with increasing salt?P<0.05?.The alanine,aspartate and glutamate metabolism were affected under salt stress.?3?In the pot experiment of different nutrient rhizosphere,the biomass and Cd content in rhizosphere soil solution of without carbon source control was significant high?P<0.05?compared with other treatments,and 2.37-3.60 times had been increased of the Cd average enrichment coefficient,these shows Escherichia had competitive edge without glucose as carbon source.?4?In the different salt stress pot experiment without additional carbon source,biomass and Cd content in the rhizosphere soil solution with bacterial inoculation treatment increased significantly compared with the control?P<0.05?,the total mobilized Cd increased by 3.17-fold,the average enrichment coefficient of the total and DTPA-extractable Cd increased by 2.63-fold under 4 g·kg^-11 salt treatment.?5?The Escherichia grew normally and promoted the accumulation of Cd in Suaeda salsa under salt stress.The content of Mg in aboveground of suaeda salsa without decrease under salt stress,there is no effect on vital function of Mg in photosynthesis of suaeda salsa.The Ca²⁺/Na⁺ration in root was increased with bacterial inoculation treatment under different salt stress,it curb the damage of salt on root cells of suaeda salsa.The K⁺/Na⁺ration in root and aboveground of suaeda salsa was heightened again with bacterial inoculation treatment under 8 g·kg^-11 salt treatment,it relieve the cations toxic effect of salt on suaeda salsa.