DEVELOPMENT OF OIL IN THE SEED OF ASCLEPIAS SYRIACA L.

Abstract

Seed of Asclepias syriaca L. was gathered at intervals during the growing season. Analyses of the seed, the oil, and the fatty acids were made, the latter by gas chromatography. About 75% of the total oil was formed in the first 5 weeks after flowering and the remaining 25% over the final 7 weeks. There was a sudden change in fatty acid composition at a middle stage of development, resulting in a fall in the percentage of hexadecenoic and octadecenoic acids and a rise in linoleic acid. Thereafter the changes were small except that linoleic showed a further increase in proportion to the total fatty acids.The weight of individual fatty acids per 1000 seeds was calculated at each stage of development. Corresponding to the change in percentage composition, there was a sharp increase in the weight of linoleic acid per 1000 seeds and an actual decrease in the weight of hexadecenoic and octadecenoic acids, between the 5th and 7th week after flowering. Between the 7th week and maturity, linoleic acid increased considerably, hexadecenoic and octadecenoic acids increased slightly, and the others remained unchanged in amount. There was a net loss of hexadecenoic acid from the 5th week to maturity. It is postulated that 9-hexadecenoic acid was converted in the seed to 11-octadecenoic acid and that oleic acid was converted to linoleic acid.