Evaluation of cadmium phytoextraction potential of peanut and the rhizospheric properties of specific cultivars

Abstract

Phytoextraction is an effective technique for removing cadmium (Cd) from contaminated farmland, thus achieving real ecological restoration. To clarify the potential of peanut phytoextraction, we designed a pot experiment to assess the Cd accumulation in peanut. In addition, the contribution of rhizosphere microorganisms in Cd accumulation was explored. The results demonstrate that the Cd content in peanut tissue ranked as follows: stem > leaf > root > needle > husk > kernel, with Cd mainly accumulated in the stems (41.92%) and leaves (40.27%). The bioconcentration factor for all cultivars was greater than 1, in agreement with the concept of phytoextraction. Cd extraction from peanut plants grown per season was appreciable, estimated as being from 28.5 g Cd ha−1 to 121.5 g Cd ha−1. Subsequently, based on the Cd accumulation characteristics, cultivars BS1016 and HY20 were identified as the high Cd-accumulating cultivars (HACs), and LH11 and LH14 were identified as the low Cd-accumulating cultivars (LACs), for further study as specific cultivars. For Cd-contaminated soil, high accumulation in HACs was associated with increased Cd bioavailability. The peanut rhizosphere attracted different microorganisms to cope with Cd stress. Compared with LACs, the rhizosphere of HACs tended to be enriched with high Cd-resistant microorganisms, which directly or indirectly participate in Cd activation (for example, Acidimicrobiia class of bacteria, Rhizophlyctis genus of fungi). Correlation analysis confirmed that Rhizophlyctis was a good choice to enhance the potential for Cd phytoextraction using peanut. This study demonstrates the advantages and rhizosphere mechanisms of using peanut for bioremediating Cd-contaminated soil, providing a new approach for remediation and targeted regulation of Cd-contaminated farmland.