Abstract: In order to clarify the effects of foliar spraying the solution with low concentration NaCl on the growth and matter accumulation of vegetables under the temperature-regulated solar greenhouse, we carried out an experiment on cucumber seedlings with two cotyledons, under two tempera-ture regimes and four concentrations of NaCl. Low-medium temperature zone (L) and medium-high temperature zone (H) were set by low tunnel with plastic film in the greenhouse. The solutions with different concentrations of NaCl, 0 mmol·L^-1 (L₀ and H₀), 5 mmol·L^-1 (L₅ and H₅), 10 mmol·L^-1 (L₁₀ and H₁₀) and 15 mmol·L^-1 (L₁₅ and H₁₅), were sprayed every day to the cucumber seedlings. The seedling growth, plant biomass, nutrient accumulation and photosynthetic gas exchange parameters of cucumber seedlings were measured at the 21th day of spraying treatment. Compared with the control groups (L₀ and H₀), NaCl spraying significantly increased dry matter and plant water content by 38.6% (L₅)-50.2% (L₁₀) and 20.8% (L₅)-52.2% (L₁₀) in L zone, 8.9% (H₅)-23.3% (H₁₀) and 8.7% (H₅)-10.1% (H₁₀) in H zone, respectively. The treatment of 10 mmol·L^-1 NaCl (L₁₀ and H₁₀) under both temperature regimes increased dry matter accumulation and plant water content than other treatments. Nevertheless, the highest normalized strong seedling index (SI) with the highest stomatal conductance (g_s) and photosynthetic rate (P_n) was only found in L₅ treatment. L₁₀ treatment promoted foliar expansion much more than H₁₀ treatment. In addition, foliar spraying NaCl with concentrations from 5 mmol·L^-1 to 10 mmol·L^-1 under both temperature regimes significantly increased the accumulation of soluble sugar, free amino acids and soluble protein, which were preferentially allocated to the stem or root of cucumber seedlings. Results of two-way ANOVA showed significant effects of both temperature and NaCl concentration on dry biomass, leaf area, P_n, plant water content, SI, g_s and free amino acid content. On the contrary, there were significant interactions between temperature and NaCl concentration in affecting plant water content, SI, g_s and free amino acid content (except leaf). In conclusion, foliar spraying with 5-10 mmol L^-1 NaCl could promote growth and physiological indices of cucumber seedlings, with the effect being higher under low temperature regime. More importantly, foliar spraying of proper concentration (L₅ and H₁₀) of NaCl could stimulate biomass accumulation more than water retention in cucumber seedlings, which would provide a relevant breeding target for high water-use efficiency in cucumber.

Key words: cucumber, NaCl, foliar spraying, temperature, matter accumulation, photosynthesis