Alleviated Toxicity of Cadmium by the Rhizosphere of Kandelia obovata (S., L.) Yong

A pot experiment was conducted to investigate the Cadmium (Cd) toxicity alleviated by the rhizosphere of Kandelia obovata (S., L.) Yong (K. obovata), using a rhizobox with Cd concentrations of 0, 12.5, 25, 50 and 100 mg kg(-1) soil. The rhizobox used to plant K. obovata was divided into five sections by nylon cloth (S2-S5). Our results showed that pH was lower in rhizosphere than in non-rhizosphere soil. Microbial biomass C (Cmic) and N (Nmic) was stimulated in rhizosphere zone, but inhibited by Cd additions. Soil enzyme activities were significantly higher in rhizosphere (S2) than in non-rhizosphere soil (S5) (p < 0.05). In addition, DTPA-extractable Cd in different rhizosphere zone soil (S2-S5) was influenced directly under different rates of Cd supply. Moreover, Cd treatments could induce the enhancement of DTPA-extractable Cd. This study suggests that Cd toxicity can be alleviated in the rhizosphere even under high Cd supply.