自然降温过程中(2006年10月至2007年3月)乐昌含笑(Michelia chapensisDandy)、红花木莲〔Manglietia insignis(Wall.)Bl.〕、浙江樟〔Cinnamomum japonicum Sieb.var.chekiangense(Nakai)M.P.Tang et Yao〕、秃瓣杜英(Elaeocarpus glabripetalus Merr.)和乐东拟单性木兰〔Parakmeria lotungensis(Chun et C.H.Tsoong)Law〕5种常绿阔叶树种的叶片相对电导率和低温半致死温度(LT50)进行了测定,并分析了各树种的LT₅₀与月平均最低温度的相关性。结果显示,在自然降温过程中,5个树种叶片的相对电导率有明显变化,除乐东拟单性木兰外,其他树种的相对电导率均呈现先升后降再升高的变化趋势。实验期内,乐东拟单性木兰和浙江樟的LT₅₀为-13℃~-19℃,抗寒能力较强,其他3个树种的LT₅₀为-3℃~-11℃,抗寒能力较弱。根据LT₅₀,可将5个树种的抗寒适应性分为抗寒性较弱期、抗寒性增强期、抗寒性最强期和抗寒性减弱期4个时期。各树种在不同月份的LT₅₀与月平均最低气温的变化趋势一致,其中乐东拟单性木兰的LT₅₀与月平均最低温度极显著相关。研究结果表明,乐东拟单性木兰和浙江樟的抗寒能力较强,在南京的适应性较强,可以广泛栽植。

The leaf relative conductivity and LT₅₀ of five evergreen broadleaved tree species, including Michelia chapensis Dandy, Manglietia insignis(Wall.)Bl., Cinnamomum japonicum Sieb. var. chekiangense (Nakai)M.P.Tang et Yao, Elaeocarpus glabripetalus Merr.and Parakmeria lotungensis (ChunetC.H.Tsoong) Law were determined in the process of natural drop in temperature from Oct. 2006 to Mar. 2007, and the correlation between LT₅₀ of different tree species and the monthly mean minimal temperature was analyzed. The results indicate thatin the process of natural drop in temperature, the leaf relative conductivity of the five tree species is changed markedly, and except P. lotungensis, the leaf relative conductivity of the other tree species appears the trend of increasing firstly, then decreasing, and increasing lastly. During the experiment time, P. lotungensis and C. japonicum var. chekiangense appear the stronger cold tolerance with LT₅₀ in - 13℃ - -19℃ , and the other three tree species exhibit the weaker cold tolerance with LT50 in - 3℃ - - 11℃ . According to LT₅₀, the cold tolerance adaptability of the five tree species is divided into four periods: weaker stage, enhance stage, strongest stage and reducing stage. The LT₅₀ change trend of different tree species indifferent months is consistent with the monthly mean minimal temperature, in which theLT₅₀ of P.  lotungensis is very significantly correlated to the monthly mean minimal temperature. It is suggested that the cold tolerance of P. lotungensis and C. japonicum var. chekiangense is stronger and their adaptability in Nanjing is stronger, both of the two tree species can be planted widely.