Association between weeds and plant growthpromoting rhizobacteria in the phytoremediation of lead-contaminated soil

Abstract

Lead is a persistent heavy metal in the soil that can accumulate in edible plants, so non-polluting strategies are required for its removal. In this study, the efficiency of weeds with associated rhizobacteria in phytoremediation of soil contaminated with lead (800 ppm) was investigated. Weeds with lead tolerance were selected, as well as rhizobacteria that promote plant growth in vitro. Several bacterial consortia (BC) were applied on three weed species, and the weight of the aboveground biomass of the weeds, the phytotoxicity of the soil after phytoremediation, as well as the parameters of the phytoremediation of lead in the soil with lower phytotoxicity, were evaluated. As a result, 20% of the weeds analyzed were tolerant to lead with indices of 0.80 (Echinochloa colona (L.) Link), 0.76 (Cyperus corymbosus Rottb.), and 0.72 (Sorghum halepense). BC solubilized phosphates, produced indole acetic acid, and increased the fresh biomass of plants (4.14-14.32%). Furthermore, the lowest level of phytotoxicity in the soil was detected in the treatment of E. colona (L.) Link with Pseudomonas spp. and Acinetobacter spp. (BC1), as well as a bioaccumulation factor of 0.1650 in the foliage, 1.0250 in the roots, and a translocation factor of 0.1611. Finally, 78.83% lead removal was determined in E. colona (L.) Link with rhizobacteria, compared to the 57.58% obtained with E. colona (L.) Link without rhizobacteria. The efficiency of the association of weeds and plant growth-promoting rhizobacteria in the phytoremediation of soils contaminated with lead was demonstrated.