Abstract: Taking one-year-old dormant shoots of Pistacia chinensis and Koelreuteria integrifoliola as test materials and the shoots of northern indigenous tree species K. paniculata as the control, the changes of their membrane-lipid peroxidation, antioxidative enzyme activity, and organic osmoregulatory substance content under artificial cooling were studied, aimed to analyze the differences of the three tree species in cold resistance. With the decrease of temperature, the ion leakage percentage of the three tree species increased in S-shape, and the SOD and POD activities decreased after an initial increase. The MDA, soluble protein, and soluble sugar contents of K. integrifoliola and K. paniculata under decreasing temperature decreased after an initial increase, while those of P. chinensis had an increasing trend. The semi-lethal temperature (LT₅₀) of K. paniculata, K. integrifoliola, and P. chinensis calculated by the Logistic equation of ion leakage percentage was -27.2 ℃, -23.7 ℃, and -27.0 ℃, respectively. Among the three tree species, K. paniculata had the strongest cold resistance, followed by P. chinensis, and K. integrifoliola.

Key words: Pistacia chinensis, Koelreuteria paniculata, K. integrifoliola, semi-lethal temperature, cold resistance