Effect Of Plant Growth-promoting Bacteria On Decreased As Accumulation Of Rice And The Mechanisms Involved

Today,with the rapid economic development of our country,people's living standards are constantly improving.However,with the rapid economic development,due to unreasonable development and uncontrolled dumping,agricultural land in China is facing serious heavy metal pollution.Soil As pollution has become the third largest pollutant that harms our country's arable land.Rice is the most important food crop in China.As entering rice will enter the food chain and cause impact on human health.Plant-promoting bacteria can not only promote the growth of crops,but also can reduce the bio-availability of As in soil to prevent the uptake of As in rice,and reduce the migration of As into the shoot and grain of rice.Through the research on plant-promoting bacteria for the phytoremediation of heavy metal-contaminated soils,theoretical basis and technical support can be provided for the remediation of As-contaminated farmland and safe production of rice.In this study,seven strains producing high IAA and siderophore and reducing As content in rice were screened from the rice varieties Nanjing 5055 and Longliangyouhuazhan.The results showed that compared with the non-inoculated control group,inoculated with the bacteria under water culture conditions could increase the biomass of above-ground tissues and roots of Nanjing 5055 by 6.4-47.1%and 4.0-209%and the above-ground tissues and roots of Longliangyouhuazhan by 6.5-43.9%and 3.3-58.0%.Inoculation of strain H3 could increase the biomass of roots and shoots of Nanjing 5055 by 3.5·72.7%and 5.7-58.5%and the biomass of the roots and shoots of Longliangyouhuazhan by 7.1-125%and 32.6-123%.The inoculation of strain F2 can reduce shoot As content of Nanjing 5055 by 38.4-58.9%and shoot As content of Longliangyouhuazhan by 60.6-66.8%.Inoculation with strain H3 decreased shoot As content of Nanjing 5055 by 18.5-56.8%and shoot As content of Longliangyouhuazhan by 9.6-24.9%.In the soil culture experiment,strains F2 and H3 were used for rice growth and As uptake at different growth and development stages.In comparison with non-inoculated control,in the rice tillering stage,inoculation treatment could significantly increase the biomass of rice plants in Nanjing 5055 and Longliangyouhuazhan by 51.27%and 81%,respectively.Rice As content was reduced by 22.63-56.57%.At the heading stage of the rice plants,the inoculation treatment increased the biomass of Nanjing 5055 and Longliangyouhuazhan by 24.1-69.1%and 20.6-167%.Significantly reduced As content(8.7-56.8%)of the two rices was observed in the presence of these strains.When rice matures,the main consideration was whether the As content in the rice grains could meet the food safety standards,the results show that at low concentration of As pollution,inoculation treatment can reduce grain As content in rice grain and meet the national food safety standards.Through the determination of soil physicochemical properties and available As content,it was found that in different growth and development stages of the rice plants,inoculation treatment could significantly increase soil pH and organic matter content,reduce the non-specific adsorption of As in soil,increase crystalline hydrated iron aluminum oxide bound As content.As for the different As forms in the paddy soils,it can be found that the distribution patterns are roughly the highest in crystalline hydration iron-aluminum oxide bound As and the lowest in non-adsorbed As.