Epicuticular wax layer

Beneath the epicuticular wax layer is the cuticle which bounds the epidermal cells and lines the sub-stomatal cavities. Structurally, it is noncellular and often multi-layered, comprising an inner region which merges with cellulose fibrils of the epidermal cell wall (cuticular layer, fibrillar in organization) (2). The chemical component of the cuticle proper is an... 

Singh, G.J.P. and Thornhill, R.A., Pharmacokinetics of dieldrin with special reference to its metabolism in the epicuticular wax layer in Calliphorn erythrocephahi, Gen. Pharmacol., 11, 283,1980. 

The outer-most layer of leaf tissue exposed to pollutants is the epicuticular wax layer. Purnell and Preece and Martin and Juniperdescribed by scanning electron microscopy the changes in structure of epicuticular waxes on the surfaces of plants as a result of weathering agents (rain, wind, dust, abrasion with foreign objects). Rentschler(20) reported that the degree to which leaves are coated with epicuticular waxes is important in the deposition and retention of solid and liquid aerosols on leaf surfaces, and in... 

The evidence above suggests that another of the means by which plants may be affected by acid rains in nature is through effects on the submicroscopic structure of the epicuticular wax layer. Such effects could in turn influence functions of the wax relating to plant water relations, protection against stress and radiation balance. 

Epidermal cells Tabular are layered sheets on surfaces of leaves and young roots, stems, flowers, fruits, seeds, ovules Secrete the fatty substance, cutin, which forms a protective layer, the cuticle cuticle covered by an epicuticular wax... 

Chen, X., and B. R. T. Simoneit, Epicuticular Waxes from Vascular Plants and Particles in the Lower Troposphere Analysis of Lipid Classes by Iatroscan Thin-Layer Chromatography with Flame Ionization Detection, . /. Atmos. Chem., 18, 17-31 (1994). 

Buschhaus, C. Herz, H. Jetter, R. (2007a). Chemical composition of the epicuticular and intracuticular wax layers on the adaxial side of Ligustrum vulgare leaves. New Phytologist, Vol.176, No.2, (October 2007), pp. 311-316, ISSN 1469-8137... 

The waxy material on the surface of the above-ground parts of plants, such as the skins of fruit and leaves of vegetables, seeds and poUen grains, is called surface or epicuticular wax. The next hydrophobic layer of the cuticle is cutin, which is a polymeric material built from hydroxy fatty acids. Wax and cutin together constitute the epicuticular lipids. In most plants, wax is not associated with cutin at all. On the surface of the underground... 

All aerial organs of higher plants are covered primarily with a thin continuous wax layer. These surface or epicuticular waxes consist of a very complex mixture of different components. In most cases these very long chained lipids are found in form of homologous series. The composition of the wax lipids shows species specific and also organ specific patterns. But numerous plants in addition contain triterpenoids,mostly pentacyclic compounds. The composition of triterpenoids from two Euphorbia species and from the leaf waxes of the trees Citrus halimii, Tilia tomentosa and Tilia x europaea will be summarized in this paper (Table 1). 

The ability of insects to withstand desiccation was recognized in the 1930s to be due to the epicuticular layer of the cuticle. Wigglesworth (1933) described a complex fatty or waxy substance in the upper layers of the cuticle which he called cuticulin . The presence of hydrocarbons in this wax of insects was suggested by Chibnall et al. (1934) and Blount et al. (1937), and over the next few decades the importance of hydrocarbons in the cuticular wax of insects was established (Baker et al., 1963 and references therein). The first relatively complete chemical analyses of the hydrocarbons from any insect, the American cockroach, Periplaneta americana (Baker et al., 1963), occurred after the development of gas-liquid chromatography (GLC). The three major components of the hydrocarbons of this insect, //-pen taco sane, 3-methylpentacosane and (Z,Z)-6,9-heptacosadiene, represent the three major classes of hydrocarbons on insects, n-alkanes, methyl-branched alkanes and alkenes. Baker and co-workers (1963) were able to identify n-pentacosane by its elution time on GLC to a standard and its inclusion in a 5-angstrom molecular sieve. 3-Methylpentacosane... 

Important solvent properties are volatility, viscosity, surface tension, and lipid solubility. The first three determine the area over which a given volume of solvent spreads the larger the area of contact between insecticide and outer cuticle layers, the larger its total penetration rate will be. Acetone does not spread very far from the site of application, because it is so volatile. Lipid solubility affects the dissolution of the wax components of the epicuticle. By disrupting this layer, e.g., depositing a drop of acetone, the insecticide could bypass the epicuticular barrier. All these effects together may explain why an optimal balance of solvent properties is necessary to obtain maximal penetration rates (Welling and Patterson, 1985). 

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