title: Improvement of rape (Brassica napus) plant growth and cadmium uptake by cadmium-resistant bacteria.
abstract: This study focuses on the screening of cadmium-resistance bacterial strains from heavy metal-polluted soils to examine their plant growth promotion and cadmium uptake in rape (Brassica napus). A large number of bacteria were isolated from heavy metal-polluted soil in Nanjing, China. Thirty isolates showing cadmium-resistance on Cd-amended medium were selected and evaluated for their potential to solubilize cadmium carbonate in solution culture. Atomic absorption spectrometer analysis showed variable amounts of water-soluble Cd (ranging from 24 to 117 mg l(-1)) released by the cadmium-resistant bacterial strains from cadmium carbonate. Qualitative analysis confirmed the presence of indole acetic acid as the auxin in the culture of these cadmium-resistant bacterial strains. Root elongation assay conducted on rape under gnotobiotic conditions demonstrated increases (up to 31%) in root elongation of inoculated rape seedlings compared to the control plants. Based upon cadmium-resistance, bio-activation of CdCO3 and growth-promoting activity, three isolates were selected for promoting plant growth and uptake of cadmium from cadmium-amended soil in pot experiments. Inoculation with the isolates was found to increase root dry weight (ranging from 8% to 20%) and shoot dry weight (ranging from 6% to 25%) of rape. An increase in cadmium content varying from 16 to 74%, compared to the non-inoculated control, was observed in rape plants cultivated in soil treated with 100 mgCd kg(-1) (as CdCl2) and inoculated with the isolates. The bacterial isolates were also able to colonize and develop in the rhizosphere soil of rape after root inoculation.
authors.affiliation: MOA Key Laboratory of Microbiological Engineering of Agricultural Environment, College of Life Science, Nanjing Agricultural University, Nanjing 210095, PR China.
authors.forename: Xia-Fang
authors.initials: XF
authors.lastname: Sheng
authors.forename: Juan-Juan
authors.initials: JJ
authors.lastname: Xia
mesh_terms: D018533:Biomass; D029688:Brassica napus / Q000254:growth & development* / Q000378:metabolism* / Q000382:microbiology; D002104:Cadmium / Q000378:metabolism*; D004352:Drug Resistance, Microbial; D018517:Plant Roots / Q000254:growth & development
chemical_list: D002104:Cadmium