Fungi and bacteria as helping agents for remediation of a Pb - contaminated soil by Onopordum acanthium

Phytoremediation is a promising method for remediation of heavy metals (HMs) contaminated environments. However, the main failures are the limited bioavailabilty of HMs such as lead (Pb) in the soil and/or suppressed plant growth in contaminated sites. These limitations specifically occur in semi-arid zone environments such as calcareous soils. Arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR) are known to enhance plant growth and survival in heavy metal contaminated soils. The main objective of this study was to evaluate enhancing soil Pb phytoremediation by Onopordum acanthium through inoculation with some AMF and PGPR. A calcareous soil was selected and spiked uniformly with different concentrations of Pb (0, 250, 500 and 1000 mg Pb kg-1 soil). The contaminated soils were then sterilized and subsequently inoculated with AMF and PGPR in which O. acanthium seeds were grown. Results indicated that inoculation of AMF and PGPR increased bioavailable Pb, shoot and root dry matter yield and Pb uptake by O. acanthium. Microbial inoculation increased the amount of Pb extracted by O. acanthium up to 2-11 times higher than the control. The amount of Pb stabilized by roots of O. acanthium was 1.75-2.71 and 1.25-1.53 times higher than control for AMF and PGPR treatments, respectively. Therefore, it could be concluded that inoculation with AMF and PGPR can be used as a promising strategy for enhancing the phytoremediation of Pb-contaminated soils by O. acanthium.