| Cadmium pollution is the most prominent HM pollution type because of its high toxicity,strong migration,and the large polluted area globally.Therefore,the remediation of soil cadmium pollution is imminent.Here,black locust that can be used for remediation Cd contaminated soil because of a tolerance of heavy metals and symbiotic nitrogen fixation.We used the plant-microbe symbiotic system that formated with Robinia pseudoacacia-rhizobium to remediate soil cadmium pollution,from locust antioxidant system and lipid peroxidation in response to nitrogen and chlorophyll content of rhizobium inoculation remediation effect of heavy metal cadmium,explore the potential application of this symbiotic system in the remediation of soils contaminated by heavy metals.Competition for nodule occupancy showed that Robinia pseudoacacia seedlings root were inoculated strains that mixed with Rhizobium radiobacter HZ6 and Ensifer adhaerens HZ14,E.adhaerens HZ14 and Mesorhizobium loti HZ76,R.radiobacter HZ6 and M.loti HZ76,R.radiobacter HZ6 and E.adhaerens HZ14 and M.loti HZ76.Based on the BOX-PCR fingerprinting patterns and nodulation rate of the formation of the nodule,we found that nodulation rate of HZ76 strain is the most,with high locust nodulation is symbiosis,dominant strains of Robinia pseudoacacia,followed by HZ6 strain.According to the results,R.radiobacter HZ6 and M.loti HZ76 strains were selected as the next experimental strains.The results showed that the growth promoting effect,in the matrix cadmium concentration of 0 and 20 and 60 mg kg-1 pollution,the HZ6,HZ76 of rhizobial bacteria and Herbaspirillum chlorophenolicum HZ10 of endophytic bacteria,and 1:1 mixed exogenous single inoculate to the root of Robinia pseudoacacia.The results showed that black locust seedlings antioxidant enzymes(SOD,POD,CAT)activity with the increase of Cd concentration showed first increased and then decreased,while the content of MDA has been showed increasing trend,the ammonia nitrogen content,chlorophyll content and plant height,root length of black locust showed decreasing trend.The content of Cd in the aboveground and root of black locust increased with the increase of Cd concentration in the stroma,and mainly accumulated in the roots.Under the moderate pollution of 20 mg kg-1,the enrichment coefficient was 0.6.With the non-inoculation treatment(A),HZ6+HZ10+HZ76 blend(RHM),single HZ6(R)increased significantly under the treatment of locust seedling height,root length,ammonia nitrogen and chlorophyll content.The results showed that R.radiobacter HZ6 strain promoted the growth and development of locust and improved the resistance and growth of Robinia pseudoacacia.In Cd contaminanted soil,the rhizobium inoculation under locust seedling antioxidant system activity of SOD,POD,CAT,nodule number showed increasing trend,while the content of MDA decreased,and mixed HZ76 with HZ10(HM),HZ6 and HZ10 and HZ76(RHM)nodulation treatment increased significantly,as the non-inoculation treatment 3.86,4.85 and 4.14 times;the locust plant height,root length,aboveground and underground dry weight,ammonia nitrogen,nitrate nitrogen and chlorophyll content showed an overall increasing trend,but RHM,R treatments is the most significant treatment effect is better than the other with bacteria and non-inoculation treatment.These results indicate that HZ76 strains and high locust nodulation and symbiosis,mixed with RHM treatments through some kind of interaction mechanism to further play the role,may also be due to R.radiobacter HZ6 strains of locust promoting effect,and M.loti HZ76 strain and the symbiotic fixation of Robinia pseudoacacia combined with improved locust seedlings resistance,further promote plant growth and development. |
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