Abstract:Some changes in the components of cucumber ( Cucumis sativus L. ) thylakoid membrane occurred before any visible chilling injury appeared when cucumber leaves were treated with chilling temperature (0 ℃, 16 h). Chilling temperature induced a specific decrease of phosphatidyl glycerol (PG) content accompanied with an increase of PS Ⅱ light-harvesting chlorophyll a/b-protein com- plex (LHC Ⅱ ) monomer content and a decrease of LHC II oligomer content in the thylakoid membrane. It also had a significant effect on the content of lipids and the fatty acid composition of each of lipid class of purified LHC Ⅱ . The PG content decreased obviously and the content of other lipid classes increased. The fatty acid composition of each lipid class from purified LHC Ⅱ was also affected. The results suggested that the changes in PG content and LHC Ⅱ supermolecular structure might be the primary indications of chilling injury.