Abstract: This paper studied the changes of polar lipid and fatty acid compositions in cucumber cotyledons under different temperature (25 ℃, 20 ℃, 15 ℃, 10 ℃) treatments. Though there was no visible injury from chilling , polar lipid compositions in cucumber cotyledons changed. Under 15 ℃, the relative content of DGDG significantly increased ; PC , PE decreased greatly. Molecular
species of main polar lipids also changed , more unsaturated molecular species in MGDG, DGDGand PC increased. These changes resulted in the increase of unsaturated fatty acids of total lipid , especially linolenic acid. Therefore , the chilling acclimation of cucumber cotyledons could be achieved by pre-exposure to 15 ℃for seven days.

Key words: Cucumber cotyledon, Polar lipid, Fatty acid, Molecular species, Low temperature