Abstract: Regarding the relative electric conductivity and relative leakage of K⁺ as a physiological indicator for the cold resistance of one-year dormant shoots of four gardening young trees, the curves of relative electric conductivity and relative leakage of K⁺ by different temperature treatments were rep resented using Logistic equation. The results showed that the relative electric conductivity and the relative leakage of K⁺ increased as a S-curves with the decreased of temperature. According to these S-shaped curves and the
Logistic equation, it could be calculated the semi-lethal temperature (LT₅₀ ) of four sticks of Idesia polycarpa, Acer negundo, Chionanthus retusu and Cornus controversa, which was - 11.5℃, - 24.9℃, - 20.7℃ and - 29.8℃ respectively. Among the four species, the cold resistance of Cornus controversa stick was the strongest, followed by Acer negundo, Chionanthus retusu and Idesia polycarpa.

Key words: Cornus controversa, Acer negundo, Chionan thusretusu, Idesia polycarpa, Relative electric conductivity, Relative leakage of K⁺, Semi-lethal temperature (LT₅₀ )