Abstract: The biennial branches of Aeschynanthus radicans variety round leaf and red flower were used as test materials. Effects of low temperature and treatment time on the relative electric conductivity (REC) were studied and the semilethal temperature (LT50) was calculated out based on Logistic equation. The results showed that REC increased as a Scurve with the decrease of temperature when the treatment time was longer than twelve hours. According to the Scurves and Logistic equation, the temperature of Scurves inflection point namely LT50 was calculated. The LT50 was between 81℃ and 101℃, which could be considered as an important index of cold tolerance in Aeschynanthus radicans．

Key words: Aeschynanthus radicans, cold tolerance, relative electric conductivity (REC), semilethal temperature (LT50)