Effects of Cd Stress on Morphological and Physiological Characteristics of Maize Seedlings

Heavy metal (HM) contamination poses a serious threat to safe crop production and human health, and different maize inbred lines respond differently to cadmium (Cd) stress. However, the morphological and physiological characteristics of maize inbred lines seedlings are not clear under Cd stress. In this study, we analyzed the agronomic traits and physiological and biochemical indices of inbred maize seedlings under Cd stress in the seedling stage using the inbred lines Kui3, CML118, Mo17, B73, and B77 as the materials. These five inbred maizes were treated with five different concentrations of Cd (0, 1, 3, 5, and 7 mg L⁻¹, respectively) were applied and the indices of the maize seedlings determined on day 15. The aboveground and belowground biomass of five maize inbred lines seedlings showed a decreasing trend under Cd stress. Leaf relative water content and SPAD values also decreased, but the overall decrease in relative water content was small, and the differences were not significant. Surprisingly, Cd stress affected the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), leading to enhanced mem-brane lipid peroxidation. The cadmium content varied greatly between varieties under Cd stress, but all of them had lower Cd content above ground than below ground, and the varieties with the highest and lowest transfer coefficients were Mo17 (0.33–0.83) and B73 (0.06–0.44), respectively. Kui3 had the greatest difference in soluble protein content under Cd stress, which showed a de-creasing trend, and the soluble sugar content was significantly decreased in general compared to that of CK. The soluble sugar content was higher than CK under Cd treatment, and the proline content of the maize seedlings of all of the inbred lines showed an increasing trend compared to CK. Overall, there were significant genotypic differences in the Cd stress response to Cd toxicity in the maize inbred lines seedlings, and, in general, this study helps us to understand the mechanism of maize inbred lines seedlings response to Cd stress. It provides a theoretical basis for the se-lection and breeding of varieties, and food safety.