Cadmium accumulation and tolerance of mahogany (Swietenia macrophylla) seedlings for phytoextraction applications

Mahogany, a high biomass fast-growing tropical tree, has recently garnered considerable interest for potential use in heavy metal phytoremediation. This study performed hydroponic experiments with Cd concentration gradients at concentrations of 0, 7.5, 15, and 30 mg L(-1) to identify Cd accumulation and tolerance of mahogany (Swietenia macrophylla) seedlings as well as their potential for phytoextraction. Experimental results indicate that Cd inhibited mahogany seedling growth at the highest Cd exposure concentration (30 mg L(-1)). Nevertheless, this woody species demonstrated great potential for phytoextraction at Cd concentrations of 7.5 and 15 mg L(-1). The roots, twigs, and leaves had extremely large bioaccumulation factors at 10.3-65.1, indicating that the plant extracted large amounts of Cd from hydroponic solutions. Mahogany seedlings accumulated up to 154 mg kg(-1) Cd in twigs at a Cd concentration of 15 mg L(-1). Although Cd concentrations in leaves were <100 mg kg(-1), these concentrations markedly exceed the normal ranges for other plants. Due to the high biomass production and Cd uptake capacity of mahogany shoots, this plant is a potential candidate for remediating Cd-contaminated sites in tropical regions.