Cadmium accumulation in Crassocephalum crepidioides (Benth.) S. Moore (Compositae) in heavy-metal polluted soils and Cd-added conditions in hydroponic and pot cultures

We have identified Crassocephalum crepidioides (Benth.) S. Moore (Compositae) as a cadmium (Cd)-accumulator plant in a heavy-metal polluted environment. In soil polluted with Cd, 5.7–17.5 mg kg−1 Cd, concentrations in the above-ground plant tissues were measured as 14.6–78.6 mg kg−1 with transfer factors in the above-ground plant tissues (concentration in above-ground tissues/soil concentration) of 1.5–6.0. No other toxic heavy metals or plant micronutrients were found to have accumulated into the above-ground plant tissues. In a hydroponic culture with 1 µmol L−1 Cd added to Hoagland's nutrient solution, Cd concentration in the above-ground plant tissues was 121.0 mg kg−1, with a transfer factor of more than 1000. In a pot culture carried out for 9 weeks in a greenhouse, the highest Cd concentration in the above-ground plant tissues, 121.2 mg kg−1, was found in a treatment with 5 mg kg−1 Cd, whereas the highest Cd content in an above-ground plant tissue, 106.1 µg, was found in a treatment with 2 mg kg−1 Cd. These results clearly showed that C. crepidioides is a Cd accumulator. In all samples, the Cd concentration in the above-ground plant tissues was higher than that in the roots. The results obtained in the present study show that this plant has a strong potential for use in phytoremediation in farm fields contaminated with Cd.