Fatty acid biosynthesis and incorporation into lipid classes in seeds and seed tissues of flax

Fatty acid metabolism in developing flaxseeds was studied by incubating whole seeds or isolated seed tissues in buffered solutions of 1‐14C‐acetate, 2‐14C‐malonate and14CO2. Lipid classes were separated by thin layer chromatography, and fatty acid labeling in phospholipids, diglycerides and triglycerides was determined by combined thin layer and gas liquid chromatographic techniques. Incorporation of14C from acetate into embryo lipids was very rapid with phospholipids and 1,2‐diglycerides becoming highly labeled in treatment times as short as 5 min. Triglycerides were labeled more slowly. Phospholipid radioactivity was largely associated with the phosphatidyl choline fraction. Oleic acid had the highest specific activity of all major fatty acids in short treatment periods. This was followed in decreasing order of activity by palmitic, linoleic, stearic and linolenic acids. As the treatment period was lengthened to 90 min or longer, linoleic and linolenic activities were markedly increased. Use of malonate or CO2 rather than acetate as the substrate increased the labeling of the saturated acids. Incorporation of14C from acetate into lipids of endosperm tissues and whole flax seeds was slower than incorporation into embryo lipids. Stearate had the highest specific activity of the fatty acids in endosperm and whole seeds.