Studies on Composition of Molecular Species of Phosphatidylglycerol in Relation to Cold-resistance of Poplar Effects of Different Low Temperature Treatments on Compositions of Polar Lipids in Cucumber Cotyledons Profiling the Changes of Molecular Species in Membrane Lipids during Coldacclimation in Winter and Spring Cultivars of Rapeseed (Brassica napus) Relationships between Phosphatidylglycerol Molecular Species of Thylakoid Membrane Lipids and Sensitivities to Chilling-induced Photoinhibition in Rice (Oryza sativa L.) HIGH PERFORMANCE LIQUID CHROMATOGRAPHY (HPLC)ANALYSIS OF MoLECULAR SPECIES OF PHOSPHATIDYLGLYCERoL FRoM LEAVES OF GINKGO BILOBA,CHINESE FIR AND POPLAR