Endophyte Pseudomonas putida enhanced Trifolium repens L. growth and heavy metal uptake: A promising in-situ non-soil cover phytoremediation method of nonferrous metallic tailing

Abstract Non-soil cover phytoremediation is the most promising method for high heavy metal contaminated, pH imbalanced and oligotrophic tailing remediation. In this study, a promising method of tailing non-soil cover phytoremediation by endophyte assisting Trifolium repens L. was established. Endophytic Pseudomonas putida strain RE02, with great heavy metal detoxification ability, could colonize in both rhizosphere and endosphere of roots. With RE02 inoculation, the germination percentage of Trifolium repens L. seeds was improved form 40.33%, 45.33% and 56.67%–60.00%, 57.00% and 73.33% in 20 mg/kg Cd, 20 mg/kg Cr and 100 mg/kg Pb contained tailing. The LC50 (concentrations causing 50% mortality of seedlings) and IC50 (concentrations inhibiting the dry biomass by 50%) of Cd, Cr and Pb increased by 6.62, 4.87, 6.27, 4.28, 22.18 and 22.63 mg/kg respectively. Moreover, RE02 inoculation improved soil fertility that the available P and available K was dramatically enhanced in endophyte inoculated groups. Thus, plant NPK concentration was significantly enhanced by 16.72%, 30.55% and 3.81% respectively, and the total heavy metal uptake by 30.03–574.58%. Taken together, Trifolium repens L. successfully grew and developed in heavy metal contaminated, oligotrophic and pH imbalanced tailing, realizing non-soil cover phytoremediation by RE02 inoculation. Overall, this study provided a feasible and promising method for in-situ non-soil cover phytoremediation of tailing, laying a foundation for ecological restoration of tailing.