Characteristics of cadmium and lead phytoextraction by sunflower (Helianthus annuus L.) in sand culture

Higher biomass producing crops such as sunflower have already been considered as a hyperaccumulating candidate. In the present study, Cd and Pb accumulation by sunflower (Helianthus annuus L.), biomass and root exudates changes in sand cultures was analyzed during 90 days. Results demonstrated that ratios of aerial biomass/ root biomass (AW/RW) in Cd or Pb treatments declined with concentrations of Cd or Pb. Optical density (OD) of root exudates at 190 nm and 280 nm observed in Cd and Pb treatments were lower than the control. In single Cd or Pb treatments, bioconcentration factors (BCF) of Cd or Pb increased with time and decreased with concentrations, the highest Cd-BCF and Pb-BCF appeared in Cd5 (21) and Pb50 (7.95), respectively. Cd-BCF or Pb-BCF showed positive correlations with AW/RW ratios and OD values, and they were negative correlated with Cd and Pb concentrations. In the complex of Cd and Pb treatments, the highest values of BCFs were observed in Cd10+Pb100. Cd-BCF values negatively correlated with AW/RW ratios and Cd concentrations; besides, Pb-BCFs were negative with both Cd and Pb concentrations. Translocation factors (IF) fluctuated irregularly with time and concentration of metals in most treatments. Cd-TF values in single Cd treatments were positive correlated with concentrations of Cd. In the complex of Cd and Pb treatments, Cd-TF showed positive correlations with OD at 280 nm, but negative with Pb concentration. Results in this paper may supply useful information for phytoremediation of soil contaminated with cadmium and lead in situ.