Cadmium Partitioning, Physiological and Oxidative Stress Responses in Marigold (Calendula calypso) Grown on Contaminated Soil: Implications for Phytoremediation

Marigold (Calendula calypso) is a multipurpose ornamental plant, but its cadmium (Cd) tolerance and phytoremediation potential is unknown. The proposed study was carried out to unravel Cd partitioning, physiological and oxidative stress responses of C. calypso grown under Cd stress. Plants were grown for four months in pots having different soil Cd levels: 0, 25, 50, 75, and 100 mg kg⁻¹ soil. Plant growth, biomass, photosynthetic pigments, leaf water contents, stomatal conductance, and membrane stability index were not decreased at 25 mg kg⁻¹ Cd. At higher levels of Cd stress, activities of antioxidant enzymes (SOD, APX, CAT, POD) increased to mitigate H₂O₂ and lipid peroxidation. Cadmium uptake in plants increased with increasing soil Cd levels, and roots accumulated a greater portion of Cd, followed by shoots and flowers, respectively. On the basis of Cd accumulation and its tolerance, it was determined that C. calypso can be successfully grown for phytostabilization of Cd contaminated soils.