Plant wax

Plant waxes are complex mixtures of hydrocarbons, alcohols, aldehydes, ketones, esters, acids, and combinations of these that are deposited in a layer outside the epidermal cells. This complex mixture of lipids probably is synthesized in the epidermal cells of most plants and exuded onto the surface. Plants usually possess cutin, a layer of cross-esterified hydroxy fatty acids which is also deposited on the surface of the epidermal cells (Kolattukudy, 1980). This layer is impregnated with waxes. The combined lipid covering not only protects the plant from invasion by foreign organisms but also helps to regulate transpiration. 

Waxes are usually isolated by boiling, scraping, or washing the outside surface with a nonpolar solvent. Surface lipids differ markedly from both seed lipids and other leaf lipids. See Chapter 2.) 

Most components of the wax layer are derived from long-chain fatty acids (C28-C34) formed by chain extension of shorter-chain fatty acids (Fig. 4.1). The shorter-chain fatty 

Long-chain alcohols are formed by reduction of long-chain fatty acids. A fatty acyl-CoA reductase has been demonstrated in cabbage, Brassica oleracea (Brassicaceae). Fractionation of the protein fraction isolated in these studies indicated that one protein fraction catalyzed acyl-CoA reduction to the aldehyde stage with NADH as the preferred reductant and another catalyzed reduction of the aldehyde to the alcohol with NADPH as the preferred reductant. The similarity of die naturally occurring fatty aldehydes and fatty alcohols of a given plant is probably due to the fact that aldehydes represent intermediates in the synthesis of fatty alcohols (Kolattukudy, 1980). 

Wax esters in plants are formed by the combination of long-chain alcohols and long-chain acids. Although this can occur in several ways, it is most probable that, in vivo, these esters are formed by action of an acyl-CoA alcohol transacyl-ase that has been demonstrated to be present by Kolattukudy (1980). 

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Sodium tungstate is used in the manufacture of heteropolyacid color lakes, which are used in printing inks, plants, waxes, glasses, and textiles. It is also used as a fuel-ceU electrode material and in cigarette filters. Other uses include the manufacture of tungsten-based catalysts, for fireproofing of textiles, and as an analytical reagent for the deterrnination of uric acid. 

Hankin L, PE Kolattukudy (1968) Metabolism of a plant wax paraffin (n-nonacosane) by a soil bacterium Micrococcus cerificans). J Gen Microbiol 51 457-463. 

Many other plant waxes have also been exploited for various uses, including esparto wax, from esparto grass Stipa tenacissima, and Japan wax, from plants of the Rhus species. 

Plant uptake, of herbicides, 13 310 Plant viruses, 3 135 Plant waxes. See Vegetal waxes Plant-wide optimization, 20 675 PlantWise software, 19 520-521 Plaque, 3 710-711... 

Octacosanoic Montanic C28 0 Major component of some plant waxes... 

DDT converts in part to p,p -DDE over time in the environment, especially in sediments [151, 171]. An example of the total aliphatic extract of a sediment from the Los Angeles Bight contaminated with p,p -DDE is shown in Fig. 11. The TIC trace shows a major UCM and the minor resolved peaks are normal alkanes (primarily from higher plant wax), with mature 17a(H),21/ (H)-hopanes (from petroleum residues as is the UCM). The mass spectrum ofp,p -DDE is shown in Fig. 12a, registering the molecular ion cluster at m/z 316-320. DDE is detected in the m/z 246 fragmentogram (Fig. lid), appearing as a small peak in the TIC trace and DDT is not detectable in this sample. 

Symptoms Severe infestations on young growing shoots can weaken plants. Wax-covered colonies are often found in leaf axils and on cactus spines. Leaves may be covered in sticky honeydew. This may in turn be covered in black sooty mold. 

Montan wax is a fossil plant wax with properties similar to natural plant waxes such as those found in carnauba palms. The material is a hard and has a high melting point. Montan wax is composed of a mixture of waxes, resins, and asphaltene-like materials. The wax is typically used in carbon inks, emulsions, polishes, and lubricants. 

In addition, the /-C33 component is relatively more important in the leaf abrasion particles. Similarly, Kavouras et al. (1998) have shown that in addition to the concentrations and ratios of the iso- and anteiso-alkanes, there are other markers associated with the alkanes in cigarette smoke. For example, the CPI for cigarette smoke was measured to be 3.44 compared to 1.41-1.66 for particles in urban and suburban areas. (The CPI for rural areas was 4.53, reflecting the contribution from plant waxes.)... 

Standley, L. J., and B. R. T. Simoneit, Characterization of Extractable Plant Wax, Resin, and Thermally Matured Components in Smoke Particles from Prescribed Burns, Environ. Sci. Technoi, 21, 163-169 (1987). 

Hentriacontane-14,16-dione, a major component of wheat, barley and other plant waxes, has been synthesized from an isoxazole intermediate (78CC962). Heating 1-nitrohexadecane in benzene solution with pentadec-l-yne and phenyl isocyanate in the presence of a catalytic amount of triethylamine gave isoxazole (447) (35% yield). Hydrogenation of the purified, crystalline isoxazole over Raney nickel in ethanol followed by acid hydrolysis of the enamino ketone afforded the dione (448) in 75% overall yield (Scheme 100). 

Surface lipids of plants. The thick cuticle (Fig. 1-6) that covers the outer surfaces of green plants consists largely of waxes and other lipids but also contains a complex polymeric matrix of cutin (stems and leaves) or suberin (roots and wound surfaces).135/135a Plant waxes commonly have C10 - C30 chains in both acid and alcohol components. Methyl branches are frequently present. A major function of the waxes is to inhibit evaporation of water and to protect the outer cell layer. In addition, the methyl branched components may inhibit enzymatic breakdown by microbes. Free fatty acids, free alcohols, aldehydes, ketones, 13-dike tones, and alkanes are also present in plant surface waxes. Chain lengths are usually C20 - C35.136 Hydrocarbon formation can occur in other parts of a plant as well as in the cuticle. Thus, normal heptane constitutes up to 98% of the volatile portion of the turpentine of Pin us jeffreyi.81... 

There are several natural non-combustion sources of PAHs. A study in 1980 by Wakeham [43] concluded that phenanthrene could be created by the dehydrogenation of steroids, retene could be produced by the diagenesis of abietic acid, and alkyl chrysenes could form from the degradation of the pentacyclic triterpenes alpha- and beta-amyrin, which are components of higher plant waxes. In this section we will look at the natural non-combustion sources of retene and perylene and how these sources might impact the Great Lakes. 

Kolattukudy P. E., Croteau R. and Buckner J. S. (1976) Biochemistry of plant waxes. In Chemistry and Biochemistry of Natural Waxes, ed. P. E. Kolattukudy, pp. 289-347. Elsevier, Amsterdam. 

Carbonaceous aerosols in the atmosphere are complex in nature and are found in both coarse particles (> about 2.5 pm) and fine particles (< about 2.5 pm). Sources of carbon-containing particles are varied and include resuspended soil particles, pollen, plant waxes, etc. in the coarse fraction, and soot particles, sorbed organics including PAHs, and secondary aerosols resulting from... 

Plant waxes are concentrated on leaves and leaf sheaths and on fruit skins, or in some exceptional cases in the seeds of plants. Most vegetable waxes contain predominantly wax esters plus a variety of other lipid materials, which affect the degree of saturation and other properties of the wax derived from different sources. Most use has been made of plant waxes in the cosmetic sector, but there is increasing interest in the use of plant-derived sterols as dietary supplements to reduce cholesterol formation. 

Waxes Waxes were classically defined as esters of a fatty acid with a fatty alcohol (e.g. beeswax), but this no longer holds as many waxes are not covered by that definition [28], Therefore, a definition based on physical properties has been proposed [29], The global market for waxes is relatively small (estimated to be 3.4 million tons/year), comprising mainly natural, fossil paraffin waxes (90%) and synthetic polyolefin and Fischer-Tropsch waxes [28], So-called recent natural waxes (animal and plant waxes) make up a small percentage with only 28,000 tons/year. 

Docosanoic Behenic 80.0 Minor component in some seed triacylglycerols and plant waxes. 

Octacosanoic Montanic 90.9 Major acid in some plant waxes. 

Plant waxes are usually found on leaves or seeds. Thus, cabbage leaf wax consists of the primary alcohols C12 and Cis—C28 esterified with palmitic acid and other acids. The dominant components are stearyl and ceryl alcohol (C26H53OH). In addition to primary alcohols, esters of secondary alcohols, for example, esters of nonacosane-15-ol, are present ... 

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