Evaluation of the cadmium phytoextraction potential of tobacco (Nicotiana tabacum) and rhizosphere micro-characteristics under different cadmium levels.

In this study, a field-scale and pot experiment were performed to evaluate the remedial efficiency of Cd contaminated soil by tobacco and explore rhizosphere micro-characteristics under different cadmium levels, respectively. The results indicated that tobacco could remove 12.9 % of Cd from soil within a short growing period of 80 d. The pot experiment revealed that tobacco could tolerate soil Cd concentrations up to 5.8 mg kg and bioaccumulate 68.1 and 40.8 mg kg Cd in shoots and roots, respectively. The high Cd bioaccumulation in tobacco might be attributed to strong acidification in the rhizosphere soil and the increase in Cd bioavailability. Rhizobacteria did not appear to be involved in Cd mobilization. In contrast, tobacco tended to enrich sulfate-reducing bacteria (such as Desulfarculaceae) under high Cd treatment (5.8 mg kg) but enrich plant growth-promoting bacteria (such as Bacillus, Dyadobacter, Virgibacillus and Lysobacter) to improve growth under low Cd treatment (0.2 mg kg), suggesting that tobacco employed different microbes for responding to Cd stress. Our results demonstrate the advantages of using tobacco for bioremediating Cd contaminated soil and clarify the rhizosphere mechanisms underlying Cd mobilization and tolerance.