Effects and mechanisms of phosphate solubilizing bacteria on enhancing phytoextraction of lead from contaminated soil by Celosia cristata L.

Phosphate solubilizing bacteria (PSB)-assisted phytoextraction can enhance the removal of toxic metals by plants from contaminated soil. Here, we investigated the promotion effects of a Pb-tolerant PSB strain, Leclercia adecarboxylata L1-5, on assisting Pb phytoextraction by Celosia cristata L.. The results showed that PSB inoculation could increase the plant shoot and root biomass by 34.90% and 55.56% when the Pb concentration was 800 mg kg−1. Pb contents in the root and shoot were enhanced 3.06 and 0.72-fold by PSB inoculation, resulting in a bioaccumulation factor (BCFaboveground) of 0.2, a translocation factor (TF) of 1.92, and a maximum total Pb extraction amount of 222.94 μg kg−1. The positive effects of PSB on Pb bioaccumulation by C. cristata L. could be attributed to its abilities of increasing soil available phosphorus. PSB inoculation benefited osmotic potential balance and membrane stability in the plant leaves, as evidenced by 2.39-fold increase of the soluble protein, 71.39% decrease of malondialdehyde and 74.31% decrease of hydrogen peroxide. The main mechanism of the enhancement of Pb phytoextraction efficiency induced by PSB inoculation could be summarized as helping Pb absorption by root elongation, and increasing endurable Pb concentration by osmotic regulation and detoxification ability optimization. This work demonstrated that PSB combined with C. cristata L. was an excellent candidate for lead extraction and could be considered as an effective way for soil lead remediation in the future.