Abstract: By comparison of thylakoid membrane lipids and their fatty acid composition, the supermolecular structure of light harvesting chlorophyll a/b-protein complex of Photosystem Ⅱ (LHC Ⅱ ) and the spectroscopic characteristics of thylakoids in winter wheat (Yanda 1817) with those in spring wheat (8901) before and after cold-hardening, it was found that after cold-hardening: (1)The trans-3-hexadeeenoic acid content of phosphatidyl alycerol (PG) in both cultivars decreased significantly, the ratio of monogalactosyl diglyceride (MGDG)/digalactosyl diglyceride (DGDG) in the thylakoid of Yanda 1817 decreased, but had no distinct change in 8901. (2)The lipid/chlorophyll ratio in thylakoids of Yanda 1817 increased significantly, but had no distinct change in 8901. (3) The LHC Ⅱ oligomer content decreased in thylakoids of both cultivars. (4) The A683/A652 ratio of the 4th derivative absorption spectra increased in both cultivars. (5)The F685/F738 ratio of low temperature (77K) fluorescence spectra of thylakoids in 8901 increased but was not affected in Yanda 1817. It was concluded that one of the major strategies of wheat to adapt low temperature was the increase of thylakoid membrane fluidity, and that the decrease of MGDG content may play an important role in stabilizing the bilayer structure of the thylakoid membrane at low temperature.

Key words: Cold-hardening, Thylakoid membrane, Lipid, Fatty acid, Photosystem Ⅱ harvesting chlorophyll a/b-protein complex