Comparison on cold resistance of different Toona sinensis provenances.

1-year Toona sinensis seedlings from ten provenances were chosen for study of their cold resistance.Relative electrical conductivity of in vitro stems was measured under different temperature treatment,and was compared with that of living ones.The turning point temperature(half lethal temperature/LT50) was calculated by logistic equation.LT50 was for reference indicator of cold resistance of tested provenances.The results showed that the relative electrical conductivity of in vitro stems of the tested provenances increased as a S-curve with decrease of temperature treatment,and the lowest of LT50 was-7.94℃,from Jinan of Shandong,and the highest,-3.88℃,from Xiapu of Fujian.The test indicated that provenance from Jinan of Shandong had the strongest cold resistance,followed by Heze of Shandong,Xixia of Henan,Ankang of Shaanxi,Nanjing of Jiangsu,Guangyuan of Sichuan,Dongkou of Hunan,Suizhou of Hubei,Qianxinan of Guizhou,Xiapu of Fujian.The result concluded that LT50 of intro and living stems was similar.