Role of Rhizosphere of Ricinus communis L. (Castor) on Nickel Phytoextraction

Investigation on the dynamics of the heavy metals in the rhizosphere has been hampered by the lack of reliable methods for sampling rhizosphere soil. The distribution of Ni in the rhizosphere was examined by using rhizobox system, composed of two components namely, central and bulk soil compartments. The rhizobox allows a clear separation of rhizosphere and bulk soil. Ricinus communis wild type plants were grown in the central compartment of the rhizobox system containing Alfisols added with 0, 50, 100, 250 and 500 mg Ni kg-1 soil. The results showed that the roots decreased the soil pH across the rhizosphere by a factor of around 0.36 units, which cause tremendous increase in DTPA extractable Ni content in the rhizosphere region compared to the bulk soil region. Nickel accumulation by Ricinus communis was increased with increasing levels of Ni in the soil.