Evaluation of suitability of common sunflower (Helianthus annuus L.) and Castor bean (Ricinus communis L.) in phytoextraction of nickel from contaminated soil

The main objective of this study was to determine the suitability of sunflower (He­lianthus annuus L. ‘Choco Sun’) and castor bean (Ricinus communis L. ‘Sanguineus Apache’) to phytoextraction of nickel from the soil, as well as evaluation of the tolerance of these species to the increasing concentration of the metal. Potential for phytoextraction of ornamental plants has been studied in two years, pot experiment in the plastic greenhouse when they were grown in mineral soil (which was slightly loamy sand) with four levels of nickel: control (native nickel content), 50 mg·dm-3 – increased content, 75 mg·dm-3 – low contamination, and 150 mg·dm-3 – medium contamination. Both species of ornamental plants were tolerant to applied concentrations of nickel, with the exception of sunflower grown in medium contaminated soil by this metal. Sunflower and castor bean are not nickel hyperaccumulators. Assessing their potential for nickel phytoextraction from the soil, it was found that it is not significant. Castor bean produces a greater aboveground mass and as a result uptake of nickel is greater compared to sunflower