Submitted to: Proceedings Sunflower Research Workshop
Publication Type: Proceedings
Publication Acceptance Date: 1/29/1999
Publication Date: N/A
Citation: Interpretive Summary: Plant surfaces are protected by a cuticular membrane that is part of the epidermis. The primary structural component of the membrane is cutin, a lipid polymer which is composed of cross-linked monomers of hydroxy, epoxy, and oxo fatty acids. Waxes are closely associated with the cuticular membrane. Epicuticular waxes cover the outer surface of the cuticular membrane, while intracuticular waxes embed the cutin polymer. The principal function of the waxes is to prohibit water loss, but they likely also play a role as a first line of defense against pathogens which invade by penetration of the cuticle. This paper describes the chemical composition of the epicuticular waxes on the surface of sunflower leaves. The main components of sunflower leaf waxes are long- chain unbranched hydrocarbons (C25-C35) and wax esters (C40-C54), with lesser amounts of long-chain, methyl-branched aldehydes (C26-C30), fatty acid methyl esters, and an uncharacterized class of lipids, possibly unsaturated, oxygenated lipids.
Technical Abstract: We used a cool, on-column injector on a capillary gas chromatograph to detect several homologous series of components in sunflower epicuticular leaf wax. The use of a cool, on-column injector reduced mass discrimination in the injector port and allowed us to detect long-chain wax esters up to more than 54 carbons in length. The main components of sunflower leaf waxes were long-chain unbranched hydrocarbons (C25-C35) and wax esters (C40-C54), with lesser amounts of long-chain, 2-methyl and 3-methyl-branched aldehydes (C26-C30), and fatty acid methyl esters. Two series of minor constituents remain unidentified. One series containing two components appeared to be multioxygenated lipids, possibly hydroxyl or epoxy compounds, based on the observed loss of two water molecules in the mass spectrum. The other unidentified series could be unsaturated, oxygenated lipids.