关键词: 牡丹（Paeonia suffruticosa Andr.）, 细胞伤害率, Logistic方程, 高温半致死温度, 耐热性

Abstract: In order to evaluate the heat resistance of tree peony（Paeonia suffruticosa Andr.） germplasm resources, 13 representative tree peony cultivars were selected as experimental materials, and the semi-lethal high temperature （LT₅₀） was studied by the conductivity method and Logistic equation. The results showed that with the treating temperatures higher step-by-step, the cell damage rate of 13 tree peony cultivars showed a typical S curve increasing trend, and the significance test conformed to the Logistic equation. The LT₅₀ of 13 tree peony cultivars ranged from 51.31 ℃ to 59.73 ℃, among which B24 had the highest LT₅₀ of 59.73 ℃, while Haihuang had the lowest LT₅₀ of 51.31 ℃. Based on sequential clustering method, 13 tree peony cultivars could be divided into 3 groups： B24, Taipinghong, B10, Fengdanhe and Fengdanbai belonged to the heat resistant type, with an average LT₅₀ of 57.70 ℃; Xiangyu, Lianhe, Wuxingyu, Daojin and Dianjianghong belonged to the moderate heat resistant type, with an average LT₅₀ of 56.32 ℃; ZB1, Pomozi and Haihuang belonged to the heat sensitive type, with an average LT₅₀ of 53.32 ℃.

Key words: tree peony（Paeonia suffruticosa Andr.）, cell damage rate, Logistic equation, semi-lethal high temperature, heat resistance