Phosphate-solubilizing bacteria improve the antioxidant enzyme activity of Potamogeton crispus L. and enhance the remediation effect on Cd-contaminated sediment

Phosphorus-solubilizing bacteria (PSB) assisted phytoremediation of cadmium (Cd) pollution is an effective method, but the mechanism of PSB-enhanced in-situ remediation of Cd contaminated sediment by submerged plants is still rare. In this study, PSB (Leclercia adecarboxylata L1-5) was inoculated in the rhizosphere of Potamogeton crispus L. (P. crispus) to explore the effect of PSB on phytoremediation. The results showed that the inoculation of PSB effectively improved the Cd extraction by P. crispus under different Cd pollution and the Cd content in the aboveground and underground parts of P. crispus all increased. The μ-XRF images showed that most of the Cd was enriched in the roots of P. crispus. PSB especially showed positive effects on root development and chlorophyll synthesis. The root length of P. crispus increased by 51.7%, 80.5% and 74.2% under different Cd pollution, and the Ca/Cb increased by 38.9%, 15.2% and 8.6%, respectively. Furthermore, PSB enhanced the tolerance of P. crispus to Cd. The contents of soluble protein, MDA and H2O2 in 5 mg·kg-1 and 7 mg·kg-1 Cd content groups were decreased and the activities of antioxidant enzymes were increased after adding PSB. The results showed that the application of PSB was beneficial to the in-situ remediation of submerged plants. Heavy metal pollution in sediment has a potential threat to the quality of water environment, and it is necessary to repair it. In-situ extraction of submerged plants is a green, low-cost and sustainable technology, but this technology has the problem of low plant biomass. In this study, a method of phosphate-solubilizing bacteria combined with submerged plant restoration was proposed, and the factors of phosphate-solubilizing bacteria promoting the growth of submerged plants and enhancing cadmium tolerance were analyzed. It provides a new idea for in-situ remediation of heavy metal pollution in sediment.