Desaturation of fatty acids in seeds of higher plants.

Photosynthesizing flax, soybean, and safflower plants were exposed to (14)CO(2) at seed-setting stage for a 1 hr period. Seed was sampled periodically thereafter and the lipids were extracted. A triglyceride-rich fraction was methanolyzed; the resultant methyl esters were analyzed by gas-liquid chromatography and assayed for radioactivity. Of the C(18) unsaturated acids, oleic was the first to acquire radioactivity, which subsequently and successively appeared in linoleic and linolenic acids. The shapes of the radioactivity-time curves provide evidence that consecutive desaturation reactions occur in the seeds of these higher plants.