Effect of cadmium tolerance and accumulation in soil on Calendula officinalis

Heavy metal pollution is a global environmental problem that threatens ecosystems and human health. Cadmium (Cd) pollution is the most prominent heavy metal pollution due to its high toxicity, strong migration, and the large area it affects globally. A pot culture experiment with five concentrations of cadmium Cd (0, 10, 30, 50, and 100 mg·kg^–1 in dry soil) was conducted to investigate Cd accumulation and tolerance in the roots and shoots of Calendula officinalis and its potential for phytoremediation. The results indicated that the growth of Calendula officinalis was not significantly inhibited and there was no evidence of toxicity. The plant height and biomass of C. officinalis first increased and then decreased with increasing Cd concentrations. When the concentration of Cd was 30 mg·kg^–1, the plant height and biomass of C. officinalis reached its peak and was significantly higher than that of control, whereas there was no significant difference between 100 mg·kg^–1 and control. The transfer coefficients of C. officinalis were less than 1 under each treatment; the enrichment coefficients of plants under all treatments were greater than 1. The accumulation of heavy metal Cd by C. officinalis increased with increases in Cd concentrations in the soil. At 100 mg·kg^–1, the accumulation of Cd per normal growth of C. officinalis reached 908 μg·plant^–1. Considering its rapid growth, high biomass, and adaptive properties, C. officinalis could be a valuable tool for the phytoremediation of Cd contaminated soils, especially in highly Cd-contaminated soil, as it can have a good enrichment effect.