A potted experiment was conducted to explore the effects of salt stress on seedling growth and photosynthetic characteristics of Euonymus hamiltonianus. The biennial seedlings were exposed to different contents of NaCl solutions (0, 2.0, 4.0, 6.0 g·L-1) for 30 days. The photosynthetic gas exchange parameters [i.e. net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs) and intercellular CO2 concentration (Ci)], biomass properties, relative electrical conductivity, pigment contents and kinetic characteristics of chlorophyll fluorescence were measured, aiming to investigate the adaptation mechanism to salt stress of E. hamiltonianus. The results showed that: Compared with CK, salt stress induced a significant decrease of Pn, Tr, Gs, limiting value of stomata(Ls) and water use efficiency (WUE), whereas it caused by a marked increase of Ci under different NaCl solutions in E. seedlings. The maximum photochemical efficiency (Fv/Fm) and the number of active reaction centers per unit area (RC/CSm) in the blade were reduced under saline treatments compared to that of in the controls, and both of the Fv/Fm and RC/CSm got significant differences. The points of K to J in the OJIL curve were increased and reached markedly differences, while the pigments contents were significantly decreased, induced by the salt conditions. Besides, compared with CK, the root-shoot ratio (R/S) and Ec had no obvious difference in the treatment of 2.0 g·L-1, while they were significantly higher in treatments of 4.0, 6.0 g·L-1. In conclusions, from the above results we could conclude that E. hamiltonianus had cer-tain tolerance to low concentration of salt stress, but higher NaCl concentration could suppressed seedling growth for it inhibited the activity of PSⅡ, reduced photosynthetic performance and use efficiency of mineral nutrients, resulting in a poor growth and even death of the plants.
