Abstract: A pot experiment was conducted to study the salt-adaptation mechanisms of Oligostachyum lubricum under different soil NaCl stress (0(CK), 1‰, 2‰, 3‰,
4‰, 5‰ and 6‰) for 45 days, with the parameters leaf abscission rate, leaf cell membrane permeability, and the uptake, transportation, and allocation of K⁺, Na⁺, Ca²⁺ and Cl^- in different organs investigated. Under 1‰-2‰ NaCl stress, the leaf abscission rate and ion leakage had no significant differences with the control; but under 3‰-6‰ NaCl stress, the leaf abscission rate and ion leakage increased significantly, and the damage increased with increasing soil NaCl concentration. Along with the increasing concentrations of Na⁺ and Cl^- in the organs of O. lubricum, the K⁺ concentration in root, culm, and branch decreased,  Ca²⁺ concentration in the three organs changed slightly, and the transportation ofK⁺ and  Ca²⁺ from root to culm and from culm to branch slowed down gradually. Due to the stronger selective absorption of K⁺ and  Ca²⁺ by leaf under 3‰-6‰ and 1‰-2‰ NaCl stress, respectively, the leaf K⁺ concentration increased rapidly with increasing soil NaCl stress while the leaf  Ca²⁺ concentration decreased after an initial increase, being of significance for keeping the ion homeostasis in leaf and maintaining the normal growth of seedlings. The significantly higher concentrations of Na⁺ and Cl^- in leaf than in other organs under 3‰-6‰ NaCl stress reduced the leaf osmotic potential, being conducive to the upward transportation of water, and also, could mitigate the salt toxicity on O. lubricum via leaf abscission.

Key words: Eucalyptus plantation soil, Soil enzyme, Soil trace element, Canonical correlation analysis