Abstract:The injury of membranes by low temperature is the most important mechanism of plant freezing in jury. There is a positive correlation between the stablity of cellular membranes and plant cold hardiness, although not all cellular membranes exhibit similar degrees of sensitivity to extracellular freezing. The membrane phospholipid biosynthesis during cold acclimation is closely related to the development of freezing resistance, but it is not initial reason, probably it is required for developing high lever of freezing resistance. The increased unsaturation of membrane lipids is only the response to low temperature and has no directly relation to cold hardiness. Also, cold-acclimation-specific protein synthesis and altered gene expression have been observed during cold acclimation of plants. The induction of freezing resistance is regulated probably at the transcriptional level.