Calcium-dependent regulation of antioxidant metabolism in maize seedlings under cadmium stress

Calcium (Ca²⁺) is an essential nutrient for plants, contributing to their improved tolerance against heavy metal stress. This study aimed to investigate how varying Ca²⁺ concentrations (0, 0.5, 2, and 5 mM) regulate maize seedling growth, physiological and biochemical traits, and cellular antioxidant defense systems under cadmium (Cd) stress, using hydroponic experiments to elucidate the mechanisms underlying Cd toxicity alleviation. The results revealed that Ca²⁺ supplementation mitigated the inhibitory effects of Cd stress on root length, dry weight, and photosynthetic pigment contents. Also, Ca²⁺ application increased the activities of superoxide dismutase and catalase, as well as the contents of glutathione and ascorbic acid in leaves, with maximum increases of 14.9 %, 65.39 %, 146 %, and 135 %, respectively, compared with the control (CK) treatment. Peroxidase activity significantly decreased under Ca²⁺ treatment, with a maximum reduction of 34.38 % compared with that under CK treatment, whereas malondialdehyde content markedly increased, reaching 19.84 % higher than that under CK treatment. Meanwhile, principal component analysis revealed that the 5 mM Ca²⁺ treatment achieved the highest composite score, indicating optimal antioxidant capacity in maize seedlings and reduced membrane lipid peroxidation caused by excessive Cd accumulation. This study enhances the understanding of the role of Ca in plant stress responses and provides insights for safe maize production in Cd-contaminated environments. However, given Cd accumulation in plants, whether the maize used in this study is suitable for animal and human consumption requires further investigation.