Plant waxes

Abstract

The surface of plants is covered with a complex mixture of lipids, often in crystalline form, called plant waxes. The chemistry, biosynthesis, catabolism and function of plant waxes are reviewed. The most common components are hydrocarbons, wax esters, free fatty alcohols and acids. Ketones, secondary alcohols, diols, aldehydes, terpenes and flavones are also found. The major function of the wax appears to be protection of the organism from water loss and other hazards of the environment. The alkanes are formed from fatty acids either by elongation followed by decarboxylation or by head‐to‐head condensation between two biochemically dissimilar fatty acids followed by specific decarboxylation of one of them. Fatty acyl‐CoA is reduced to the aldehyde which in turn is reduced to the alcohol. The alcohol is then esterified with acyl moieties from acyl‐CoA or phospholipids. Plant waxes undergo very little catabolism in plants but animals can degrade them to a limited extent and microorganisms readily degrade them.

The temporal dynamics of terrestrial organic matter transfer to the oceans : initial assessment and application

“…Small mountainous rivers draining the world's active margins have been recently hypothesized to deliver > 40 x 1012 g of fossil organic carbon to the oceans annually based on the assumption that depleted A' 4 C values for TOC in their suspended loads and adjacent shelf sediments are primarily attributable to the presence of a petrogenic endmember Komada et al, 2004;2005 Organic compounds derived from terrigenous sources and subsequently preserved in marine sediments include homologous series of alkyl lipids such as alkanoic (fatty) acids, alkanes, and alcohols, various derivatives of steroid and hopanoid skeletons, and macromolecules such as lignin, cutin, and cellulose from rigidifying tissues Kolattukudy, 1969;Meyers, 1997, and references therein; Kunst and Samuels, 2003). The abundance and distribution of these molecular proxies are increasingly being employed in studies of past and present OC flux (e.g.…”

“…Here I construct A14C profiles of several alkanoic (fatty) acid homologues, and combinations thereof, from sediment cores spanning the twentieth century. Long chain (> nC 24 ) fatty acids found in sediments are generally thought to derive from the epicuticular coating of vascular plant leaves Kolattukudy, 1969;Kunst and Samuels, 2003;Lemieux, 1996), and inherit the A14C signature of the CO 2 from which they are synthesized. Any departure in the A 14 C signatures of these leaf waxes from that of the atmosphere can be attributed to retention in (perhaps a broad array of) terrestrial environments such as soils, wetlands, and/or other freshwater sediments (Figure 4.1).…”

In vitro studies of the metabolism of [14C]-n-alkanes using ruminal fluid of sheep as substrate

“…The purpose of this latter step was to ensure the full incorporation of 14 C to the plant waxes. Good revisions on the biosynthesis of plant wax n-alkanes can be found in Hawke (1973), Kolattukudy (1970), Lester (1979) or Kunst and Samuels (2003), among others. The grass was harvested with scissors and placed in a small polyethene bag for storage at 2208C in the radioisotope laboratory at the Macaulay Institute, prior to freeze-drying and extraction of wax components.…”

Sedimentary lipid biogeochemistry of an hypereutrophic alkaline lagoon

“…These are constituents of cuticular waxes of higher plants (KOLATTUKUDY, 1970), and their occurrence in aquatic environments is usually associated with terrestrial contributions (FARRINGTON and QUINN, 1973). The presence of higher plant lipids is a general feature of lacustrine sediments from temperate regions which is observed irrespective of the depositional conditions.…”