INCORPORATION OF C14OR P32INTO THE PHOSPHATIDES OF RUNNER BEAN LEAVES

Abstract

The phosphatide content of primary leaves of runner bean increased linearly with time, between the 8th and 20th day of development, at a rate proportional to the growth of the leaves.Detached leaves incorporated C14into the total lipids (pigments, non-phosphatides, and phosphatides) when supplied with C14O2in the light for 1 minute followed by a 30-minute period in the light or dark in tracer-free air and when supplied with pyruvate-2-C14or acetate-1-C14in the light. P32was incorporated into the phosphatides after orthophosphate-P32was supplied both in the light and dark. With each precursor, radioisotope was incorporated into the four phosphatide fractions obtained by chromatography of the total lipids: inositol–carbohydrate phosphatides (Fraction I), phosphatidyl ethanolamine – phosphatidyl serine (Fraction II), an unknown phosphatide (Fraction III), and lecithin (Fraction IV).Distribution of radioactivity among these phosphatide fractions and among the phosphatide moieties varied greatly with the precursor supplied. Thus, with C14O2as precursor, Fraction I and III had the highest specific activities, and C14entered both the water-soluble moieties and the fatty acids in all of the phosphatide fractions. With pyruvate-C14or acetate-C14, lecithin was most highly labelled, and C14was found almost exclusively in the fatty acids of the phosphatides. With orthophosphate-P32, Fraction III had the highest specific activity. The bearing of these findings on the metabolism of phosphatides in leaves is discussed.