Role of PGPB in phytoremediation of heavy metal contaminated soils and the biochemical responses of Vicia faba-soil system

Abstract

Phytoremediation is an eco-friendly and promising strategy for heavy metal (HM) removal from polluted soils. The present study focuses on assessing the potential of faba bean - plant growth promoting bacteria (PGPB) symbiosis in phytoremediation and soil fertility restoration. Vicia faba L. var. minor was inoculated with efficient and HMs resistant PGPB, and was cultivated in three soil samples differently contaminated by HMs; through the addition of different concentrations of copper (Cu), zinc (Zn), lead (Pb) and cadmium (Cd).An increase in shoot dry weight (SDW) and nodule dry weight (NDW) was observed after bacterial inoculation mostly in C1 soil. Furthermore, the inoculation effect was marked in the moderately contaminated soil, where a significant increase in shoots Zn, Pb and Cd accumulation (by 56%, 66% and 441, respectively). Likewise, in C1, Cu, Zn, Pb and Cd content in plants was more pronounced in inoculated V. faba by 54%, 217%, 179% and 319%, respectively, compared to the non-inoculated. Nevertheless, HMs induced a significant increase in roots antioxidant enzyme such as superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GR) and inoculation further enhancing their activities essentially in C1. Moreover, PGPB considerably reduced Cu and Cd available fractions by 31% and 53%, in C1 and C2, respectively, and increased soil nitrogen (N) and phosphorus (P) content, urease and β-glucosidase activities. The obtained results highlight the effectiveness of V. faba- PGPB symbiosis in the reclamation of low and moderately Cu, Cd and Zn contaminated soils. The consortium could be used as biofertilizer to improve soil quality and fertility.