Abstract：The increase of membrane permeability in plant cell results to imbalance in cellular homeostasis and expression of heat shock gene. As fatty acids are the basic elements of the cell membrane, the content and the saturation of lipid are related to the cell membrane stability under high temperature. Two genotypes of Triticum aestivum L. tolerant TMA107 and susceptible Chinese spring(CS), were chosen according to their genetic background diversity in thermotolerance. Membrane permeability, the fluorescence ratios Fv/Fm，fatty acids composition (C14:0, C16:0, C16:1c, C16:1t, C18:0, C18:1, C18:2 and C18:3) and transcript of fatty acid desaturase gene (FAD7) under high temperature were quantified. Increase of membrane permeability and reduction of fluorescence ratios Fv/Fm and trienoic fatty acids content were observed in both genotypes. However, changes in unsaturated fatty acids content in Chinese spring were significantly higher than that of TAM107. These indicated that the membrane system of heat resistant genotype wheat is much more stable under heat stress than heat sensitive genotype. The expression of FAD7 was more sensitive to heat stress in CS than in TAM107, and as a result, the content of trienoic fatty acids in membrane changed much more in CS after heat stress . This indicated that the susceptible genotype CS is more sensitive to high temperature than tolerant genotype TAM107 on transcript level. The observed changes on trienoic fatty acid content under high temperature may be a positive trait for heat tolerance qualification.
