Abstract:To explore the effect of Si nutrition on cold resistance of red sandalwood (Pterocarpus santalinus), one-year-old seedlings applied silicon (Si) for 180 d were suffered (-3±0.5)℃ stress for 24 h, and then recovered for 90 d in greenhouse, the growth status, leaf photosynthetic parameters and activities of four key enzymes related carbon assimilation of the seedlings were studied. The results showed that the seedlings applied Si were strong, growth recovery was fast after cold stress, the cold resistance was significantly improved. After applied Si, the decreases of chlorophyll content and Chl a/b of seedlings caused by cold stress were significantly inhibited, the apparent electron transfer rate (ETR), actual photon efficiency Y(Ⅱ) and PSⅡ regulatory energy dissipation Y(NPQ), and reduced the proportion of PSⅡ non-regulated energy dissipation Y(NO) and non-photochemical quenching (NPQ) were all promoted, and the leaf photosynthetic rate (Pn), stomatal conductance (Gs) and water use efficiency (WUE) of red sandalwood seedlings under cold stress increased after applied Si. The activities of four key enzymes related carbon assimilation, such as ribulose-1,5-bisphosphate carboxylase (Rubisco), fructose- 1,6-phosphatase (FBP), fructose-1,6-bisphosphate aldolase (Ald) and phosphoenolpyruvate carboxylase (PEPC), of seedlings applied Si were significantly higher than those of non-applied Si. Therefore, application of the appropriate amount of Si benefits the integrity of photosynthetic membrane structure and stability of physiological functions of seedlings under cold stress, and it is an effective nutrient management measure improving the cold resistance and coping with cold stress of red sandalwood seedlings.