Lead tolerance and phytoremediation efficiency of Cercis canadensis and Tetradium daniellii

Lead (Pb) is one of the most hazardous heavy metals, posing serious threats to plants, animals, and human health. To mitigate its environmental impact, phytoremediation using plants to extract, stabilize, or detoxify pollutants offers a sustainable and cost-effective solution for soil rehabilitation. This study aimed to evaluate the tolerance and phytoremediation capacity of Cercis canadensis and Tetradium daniellii seedlings grown in lead-contaminated soils. Two-year-old plants were exposed to lead acetate solutions at concentrations of 100 mg/kg and 300 mg/kg of soil, while control plants received only water. Plant physiological responses were assessed one week, one month, and two months after exposure. The content of chlorophylls, carotenoids, and malondialdehyde, as well as peroxidase activity, were determined spectrophotometrically. Photosynthetic performance was measured using fluorimetry, and the distribution of mobile lead compounds in leaves, stems, and roots was analyzed by atomic absorption spectrophotometry. Both species demonstrated high tolerance to lead exposure, with minimal impairment of the photosynthetic system. Notably, a short-term increase in chlorophyll content and stimulated shoot growth were observed in plants treated with 100 mg/kg Pb. Lead accumulation in C. canadensis occurred predominantly in the roots, whereas T. daniellii accumulated lead in both roots and stems. These findings indicate that both species possess considerable resistance to lead stress and potential for phytostabilization and phytoextraction. Consequently, Cercis canadensis and Tetradium daniellii can be recommended as effective ornamental species for greening and rehabilitating lead-polluted urban and industrial areas.