Abstract:The fatty acids and the phospholipids in membrane lipid of two poplarvarieties: chill-resistant P. euramericana cl. I-45/51 and chill-sensitive P.deltoides Bartr. Cv. "Lux"I-69/55 were analysed. There is an evident differe-nce in the unsaturated degrees of the fatty acids between the two Varieties,linoleic acid is the dominant component in the chill-resistant variety, whilepalmitic acid is the major one in the chill-sensitive variety. Index ofUnsaturation of Fatty Acid (IUFA) can be used as a standard to evaluate thechilling resistance of poplar. The phospholipid compositions in two varietiesare similar, they are phosphatidyl choline (PC), phosphatidyl inositol (PI),phosphatidyl ethanolamine (PE), and phosphatidyl glycerol (PG). There areno apparent differences in the distribution of the four phospholipid componentsand the total content of phospholipid between these two varieties, so phospho-lipid composition can not be used as a standard of chilling resistance for po-plar.