Elevated CO2 improves root growth and cadmium accumulation in the hyperaccumulator Sedum alfredii

Abstract

This study examined the effect of elevated CO2 on plant growth, root morphology and Cd accumulation in S. alfredii, and assessed the possibility of using elevated CO2 as fertilizer to enhance phytoremediation efficiency of Cd-contaminated soil by S. alfredii. Both soil pot culture and hydroponic experiments were carried out to characterize plant biomass, root morphological parameters, and cadmium uptake in S. alfredii grown under ambient (350 μL L−1) or elevated (800 μL L−1) CO2. Elevated CO2 prompted the growth of S. alfredii, shoot and root biomass were increased by 24.6–36.7% and 35.0–52.1%, respectively, as compared with plants grown in ambient CO2. After 10 days growth in medium containing 50 μM Cd under elevated CO2, the development of lateral roots and root hairs were stimulated, additionally, root length, surface area, root volume and tip number were increased significantly, especially for the finest diameter roots. The total Cd uptake per pot was significantly greater under elevated CO2 than under ambient CO2. After 60 d growth, Cd phytoextraction efficiency was increased significantly in the elevated CO2 treatment. Results suggested that the use of elevated CO2 may be a useful way to improve phytoremediation efficiency of Cd-contaminated soil by S. alfredii.