Abstract: Soils with different pH were artificially prepared by mixing various proportions of non-sodic and sodic soils, and pot experiment was conducted to investigate the biological characteristics and physiological responses of Leymus chinensis seeded in the prepared soils. The results showed that soil pH≤8.50 was beneficial to the growth of L. chinensis; when the pH was above >8.50, the tillering number and shoot dry mass had a decreasing trend; and when the pH was 9.78, the total plant number and shoot dry mass were decreased by 42.0% and 74.1%, respectively, compared with the control (pH=7.15). Under saline-alkali stress, the water content, soluble sugar content, chlorophyll content, and K⁺ concentration in shoot decreased, while the Na⁺ concentration and the conductivity of cytoplasmic membrane increased obviously. The K⁺/Na⁺ ratio in shoot decreased from 28.5 at pH 7.15 to 1.6 at pH 9.78. The higher concentration of K⁺ and higher ratio of K⁺/Na⁺ in shoot might be the main physiological mechanism of salinealkali tolerance of L. chinensis.

Key words: Life history, Population regulation, Immunocompetence, Trade-off