Effect of Temperature on the Short Chain Fatty Acid-induced Inhibition of Lettuce Seed Germination.

In lettuce, Lactuca sativa short chain fatty acids (C(6) - C(9)) vary in their effectiveness as inhibitors of germination according to temperature; the higher the temperature, the greater the inhibition. A linear relationship exists between temperature and the dose causing half-maximal germination. Nonanoic (C(9)) acid is the most effective.When extrapolated to the abscissa, really zero concentration of acid, the regression lines intercept at 36.8 C +/- 2.6 C. It may be that at this temperature the whole membrane becomes fluid without acid being present but with acid there was complete fluidizing at lower temperatures the degree of fluidity being determined by the amount and type of acid present. This speculation distinguishes between the fluidizing of the bulk lipids and the character of the lipid layer that may be around certain key membrane proteins.