Abstract: The purpose of this paper is to investigate the regulating mechanism of calcium chloride （CaCl2）and salicylic acid（SA）on the photosynthesis of cucumber（Cucumis sativa L.）seedlings under suboptimal temperature and low light intensity.‘Jinyou 3’cucumber seedlings were used as the experimental materials. Seedlings were pre-treated with either distilled water，10 mmol ? L-1 calcium chloride（CaCl2）and 1 mmol ? L-1 salicylic acid（SA）for 3 d. Afterwards，the pre-treated and non-pretreated（control）seedlings were displaced into growth chambers and treated under suboptimal temperature （day/night temperature is 18 ℃/12 ℃）and low light intensity（100 μmol ? m-2 ? s-1）. The results showed that suboptimal temperature and low light intensity decreased the growth，photosynthetic rate（Pn），theactivities and mRNA expressions of ribulose 1,5-biphosphate carboxylase/oxygenase（Rubisco），fructose-1,6-bisphosphatase（FBPase），glyceraldehyde-3-phospha -ate dehydrogenase（GAPDH），fructose-1,6-bisphosphate aldolase（FBA）and transketolase（TK）significantly. 10 mmol ? L-1 CaCl2 and 1 mmol ? L-1 SA led to an increase in the growth volume，Pn，activities and mRNA expressions of Rubisco，FBPase，GAPDH，FBA and TK. The results suggest that CaCl2 and SA have beneficial effects on the adaptation to low light and suboptimal temperature in cucumber seedlings. It speculates that this adaptation might be related to the observed increase in the gene expression and activity of the Calvin cycle enzymes.

Key words: cucumber, photosynthetic rate, mRNA expression, calvin cycle enzymes, solar-greenhouse