Abstract: To understand the responses of Apocynum venetum to various levels of salt stress, we conducted the experiment. The pot experiments were in a net room to study the effects of NaCl at different concentrations (100–400 mmol·L^–1) on plant growth and several physiological characteristics of A. venetum. An amount of 100 mmol·L^–1NaCl reduced the plant fresh weight significantly but did not affect plant dry weight. The fresh weight and dry weight of A. venetum decreased with increasing NaCl concentrations. Leaf malondialdehyde content, electrolyte leakage percentage and Na⁺ content in root and shoot were all elevated. K⁺ content in root and shoot and Ca²⁺ content in shoot decreased significantly. However, Ca²⁺ content in roots grown under all NaCl stresses was unaffected. Ratios of K⁺/Na⁺ and Ca²⁺/Na⁺ in plant decreased with increasing NaCl concentration. Salt stress markedly promoted the selective absorption of K⁺ and Ca²⁺ in root and selective transportation of K⁺. Contents of proline and soluble sugar increased with increasing NaCl concentration (≤200 mmol·L^–1NaCl). Nevertheless, contents of proline and soluble sugar gradually decreased with stresses increasing (>200 mmol·L^–1NaCl). In general, adaptation to salinity (≤200 mmol·L^–1NaCl) in A. venetum was mainly caused by inorganic ion accumulation, organic solute synthesis, strong K⁺, Ca²⁺ selective absorption and transportation.

Key words: Apocynum venetum, growth, physiological response, salt stress