Effect of Silicon on Tobacco Growth and Antioxidant Defense System Under Cadmium Stress

Tobacco (Nicotiana tabacum L.) is an economically important crop in China. The risk of cadmium (Cd) pollution is increasing, making the mitigation of Cd stress critical for the safe production of tobacco. Silicon (Si) has been demonstrated to enhance plant growth under heavy metal stress. To elucidate the physiological and biochemical mechanisms by which Si alleviates Cd stress in tobacco, this study conducted a hydroponic experiment with three replicates using tobacco variety Yunyan 87 and employed one-way analysis of variance (ANOVA) for statistical analysis. The effects of Si on tobacco growth and the antioxidant defense system under Cd stress were investigated. The results showed that Cd stress significantly inhibited tobacco growth, increased Cd accumulation, and induced oxidative damage. Si treatment alleviated Cd stress in tobacco, increased biomass, reduced Cd concentration in different plant organs, and decreased the Cd translocation factor and bioconcentration factor. Meanwhile, the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in tobacco roots and leaves were significantly enhanced, while the activities of ascorbate peroxidase (APX) and glutathione reductase (GR) were also elevated. The accumulation of ascorbic acid (AsA) and glutathione (GSH) increased, and malondialdehyde (MDA) concentration decreased. Overall, these results demonstrate that Si mitigates Cd stress in tobacco by limiting Cd accumulation and transport and by coordinately activating both enzymatic and non-enzymatic antioxidant systems.