Abstract: By using pressvolume technique, this paper studied the seasonal changes of water potential at saturated point (Ψ_s^sat), water potential at turgor loss point (Ψ_s^tlp), relative osmotic water content at turgor loss point (ROWC^tlp), relative water content at turgor loss point (RWC^tlp), relative content of apoplastic water (AWC) , bound water/ free water (V_a/V_o), and the difference between Ψ_s^sat andΨ_s^tlp (ΔP) of Reaumuria trigyna growing on heavy solonchack, nonsalinized soil, and saline soil. The seasonal changes of Ψ_s^sat and Ψ_s^tlp were in order of May>July>September, while those of AWC, V_a/V_o, andΔP were in opposite sequence, indicating that the water deficit resistance ability of R. trigyna enhanced with season, being consistent with its growth rhythm. Comparing with other xerophytes, R. trigyna had very low Ψ_s^sat and Ψ_s^tlp, presenting its strong ability of maintaining high osmotic pressure and low water potential. Based on the water parameters measured in three months, and by using the subordination function of fuzzy mathematics, the water deficit resistance ability of R. trigyna was evaluated, which was the strongest on heavy solonchack, followed by on nonsalinized soil, and on saline soil.

Key words: Reaumuria trigyna, press-volume technique, water parameter, seasonal change, habitat, stress resistance, greenhouse, tomato, development period of fruit, nighttime temperature, photosynthetic production.