Abstract:To study the photosynthetic characteristics and antioxidative enzyme system of cucumber in calcareous soil under cadmium (Cd) stress is important for the control of Cd in plants. This paper explored the photosynthetic parameters such as net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), and intercellular CO2 (Ci) of cucumber in Cd-contaminated soil under the intervention of silicon, Chlorophyll content, changes in antioxidant enzyme systems such as MDA, SOD, POD, and CAT. The results showed that:compared with the control, Cd alone, Pn, Gs, Tr and chlorophyll content decreased, but Ci increased. However, after silicon intervention, the total amounts of Pn, Gs, Tr and chlorophyll significantly increased, and the content of Ci was reduced. For example, when the Cd content was 5 mg/kg, and the silicon application amount was 100~200 mg/kg, Pn, Gs, Tr, and chlorophyll increased, and Ci decreased, compared with the control. However, the difference between 100 and 200 mg/kg of silicon was not obvious, and the effect of 300 mg/kg of silicon was best. For the antioxidant enzyme system, compared with the control, when the soil Cd content was 3~5 mg/kg, the activities of the three antioxidant enzymes were significantly inhibited. But, the introduction of 200~300 mg/kg of silicon couldsignificantly increase the activity of SOD, POD, CAT, but decrease the MDA value. It could be concluded that application of silicon can significantly improve the photosynthetic characteristics and antioxidant enzyme system of cucumber leaves under Cd stress. Application of a small amount of silicon fertilizer has obvious application prospects to relieve Cd toxicity in plants.