Transcriptional, physiological and ultrastructure levels revealed silicon enhanced cadmium detoxification and functional compound accumulation in pakchoi

Soil cadmium (Cd) pollution significantly reduces both the yield and quality of pakchoi, posing potential health risks to consumers. This study aims to investigate the mechanism by which silicon (Si) mitigates Cd accumulation and enhances the yield and quality of pakchoi. The growth of pakchoi was inhibited when treated with 25 μmol L −1 CdCl 2 ; however, the application of 1 mmol L −1 Na 2 SiO 3 significantly alleviated the inhibitory effects of Cd. Transcriptomic and physiological experiments demonstrated that Si application reduced Cd content in the roots and shoots by 39.96% and 61.59%, respectively, by modulating the expression of genes involved in Cd absorption and transport. Following Si application, the activities of catalase and ascorbate peroxidase increased by 2.79-fold and 2.01-fold. This enhancement in antioxidant capacity contributed to improved Cd tolerance. After Si treatment, the nitrate content in pakchoi leaves decreased by 66.14%. In contrast, the levels of vitamin C, glucosinolates, carotenoids, calcium, iron and zinc increased by 89.90%, 43.90%, 111.16%, 14.73%, 51.46% and 82.91% respectively. This enhancement in nutrient composition markedly improves the overall nutritional quality of pakchoi. These results indicate that Si application is an effective method to alleviate Cd stress in crops, providing a viable approach to enhance food safety in Cd-polluted areas. • Si alleviated Cd toxicity and improved the yield and quality of pakchoi under Cd stress. • Si inhibited the absorption of Cd and decreased the accumulation of Cd in the roots and shoots. • Si improved the activity of antioxidant enzymes, reduced the accumulation of ROS. • Si alleviated Cd-induced chlorophyll degradation and promoted photosynthesis. • Si decreased the nitrate content, increased beneficial nutrients content in pakchoi.