Influence of microbial inoculation of a Pb-contaminated soil on growth, some physiological properties, and uptake and translocation of Pb, Fe, and Zn by Centaurea (Centaurea cyanus)

Arbuscular mycorrhizal fungi (AMF) and plant growth promoting rhizobacteria (PGPR) affect plant growth and tolerance under environmental stresses such as soil contamination with metals. In this study the effect of inoculation with selected strains of AMF (a mixture of Glomus species including G. intraradices, G. mosseae and G. fasciculatum) and PGPR (a mixture of Pseudomonas species includeing P. putida, P. fluorescens, and P. aeruginosa), on uptake and translocation of Pb, Fe and Zn, height, yield and some physiological properties of Centaurea (Centaurea cyanus) was evaluated in a Pb contaminated soil. This study was carried out in greenhouse condition as a factorial experiment based on a randomized complete block design with two factors including Pb concentration (in four levels) and microbial treatment (in two levels) and in three replications. Soil was contaminated with Pb concentrations of 0, 250, 500 and 1000 mg kg-1 and was then sterilized and inoculated with the AMF or PGPR. Results indicated that with increasing soil Pb concentration, plant growth, shoot Fe and Zn concentration, chlorophyll and carotenoeids contents and leaf relative water content decreased, while proline content and the plant Pb concentration increased. The microbial inoculation resulted in a significant increase (P≤0.05) in plant growth, uptake and translocation of Pb, Fe and Zn, an improvement of plant water uptake and conservation and increase in contents of the plan photosynthetic pigments and proline. Mean shoot dry biomass of AMF and PGPR inoculated treatments were, respectively, 2 and 1.2 order of magnitude higher compared to the corresponding blank treatments. It could be concluded that microbial inoculation results in improved plant growth and increased tolerance against Pb toxicity.