Effects Of Plant Growth-Promoting Bacteria And Edta On The Growth And Heavy Metal Accmulation Of Plants

Phytoremediation is ever-increasing attention due to its cost-effective, convenient operation and friendly-environment for remediation of heavy metal-contaminated soils, large number of active rhizosphere microorganisms affect growth and heavy metal accumulation of plants in heavy metal-polluted environment by many approaches, and then improving phytoremediation efficiency. In hardly soluble heavy metals (such as Pb)-contaminated soil, heavy metal bioavailability is very low, which restricts the remediation efficiency of the plant. Therefore, screening of heavy metal tolerance and plant growth-promoting bacteria to study the effects and mechanism of bacteria and EDTA on the growth and heavy metal accumulation of plant will further clarify mechanism of plant’s heavy metal accumulation and offer the new technical way and experimental and theoretical bases for application of plant-microbe remediation.In this study,4plant growth-promoting bacteria strains were screened out from55maize rhizosphere bacteria kept in our laboratory. Biological characteristics of the strains T12T55、T56and T57were studied. The results showed that the strains could be resistant to a variety of heavy metals (Pb and Zn、Cu、Cd) and antibiotics (Km、Amp、Str、Tc and Cm); strains T12and T57could produce ACC deaminase, the four strains could produce IAA and siderophore. The four strains were identified as Bacillus、Pantoea and Brevibacterium based on16S rRNA gene sequences analyses.The effect and mechanism of the growth-promoting rhizosphere bacteria on microbial-assisted phytoremediation of heavy metal polluted-soil were investigated in field experiment in Tangshan copper mine field, then screened of target strains tested. The results showed that inoculation of the tested strains T12. T55、T56and T57promoted the growth of maize and increased exchang forms of copper in rhizosphere soil of maize. The bacterial inoculation increased the invertase activity, decreased soil urease activity and had little effect on pH of soils. PCR-DGGE revealed that the endophytic bacterial community in the roots of maize was influenced by the test strains compared with the rhizosphere bacterial community of the maize. Two different efficient strains (Bacillus sp.T12and Brevibactrium sp.T56) were selected based on the promotion of plant growth and heavy metal accumulation of plant.Brassica napus was selected to investigate the effects of plant growth-promoting bacteria T12、T56and EDTA on the growth and Pb accumulation of the plants in pot experiment. The results showed that EDTA-bacteria interaction could promote the growth and Pb accumulation of rape. Inoculation with strains promoted the plant growth and the accumulation of Pb in root and shoot tisseus. Compared to the non-inoculated control, the dry weights of the rape treated with strains were increased from27.97%to112%(shoot) and from13.89%to63.75%(root) and the Pb contents of rape increased from53.87%to398%. The Pb contents of the rape treated with EDTA were increased from842%to2153%, compared to the control. Treatment with the combination of one-half dose of the tested bacterium and EDTA helped the plants to accumulate the same or more Pb compared to the EDTA treatment alone.