Cuticle materials

Upper Surface. All ESCA spectra for the upper surface of the brown leaves show that they are covered by a layer dominated by the hydrocarbon parts of the cuticle material, which is incapable of preventing significant amounts of air-induced oxidation. Although reduced in comparison to the other leaf surfaces, the limited amount of oxygen found by grazing incidence is predominantly on the outermost surface. The waxy esterified parts of the cuticle appear to be dissipated and thus, as previously mentioned, all surfaces exposed to air, even the most non-reactive, are subject to at least some O2- and H20-induced oxidation. Thus, what we call natural passivation is indicative of extensive oxidation, which prevents further corrosive oxidation [33, 202]. Hence, in the case of the brown leaf we observe the botanical equivalent of metal corrosion. 

Wool fibers have a very complex morphological stmcture. They can be considered as biological composite materials, in which the various regions are both chemically and physically different (87). Fine wool fibers contain two types of cell those of the internal cortex and those of the external cuticle. 

The major site of occurrence of polyesters in plants is the cuticle where the insoluble polymer constitutes a major barrier. This material present in the skin of fruit constitutes a significant part of the waste produced in fruit processing. The very large quantities of the cutin-rich agricultural wastes that are produced may be a source of high value polyesters. Since the insoluble polymer is relatively re-... 

The aliphatic components of SOM, derived from various sources, tend to persist in soil (Almendros et al. 1998 Lichtfouse et al. 1998a Lichtfouse et al. 1998b Mosle et al. 1999 Poirier et al. 2000). The principal source of aliphatic materials in soil is plant cuticular materials, especially cutin, an insoluble polyester of cross-linked hydroxy-fatty acids and hydroxy epoxy-fatty acids (Kolattukudy 2001). Some plant cuticles also contain an acid and base hydrolysis-resistant biopolymer, comprised of aliphatic chains attached to aromatic cores known as cutan (Tegelaar et al. 1989 McKinney et al. 1996 Chefetz 2003 Sachleben et al. 2004). 

Liptinites were made up of hydrogen-rich hydrocarbons derived from spores, pollens, cuticles, and resins in the original plant material. Vitrinites were made up of wood, bark, and roots and contained less hydrogen than the liptinites. Inertinites are mainly oxidation products of the other macerals and are consequently richer in carbon. The inertinite group includes fusinite, most of which is fossil charcoal, derived from ancient peat fires. 

Note These (maceral) constituents can be identified and quantitatively measured by examining thin sections or polished surfaces under a microscope, and reflect the nature of the primordial source material as well as the conditions under which it was deposited. Vitrinites derive from humic gels, wood, bark and cortical tissues eoi lnites are the remains of fungal spores, leaf cuticles, algae, resins and waxes and inertinites comprise unspecified detrital matter, "carbonized" woody tissues and fungal sclerotia and mycelia. 

High-resolution 13C NMR studies have been conducted on intact cuticles from limes, suberized cell walls from potatoes, and insoluble residues that remain after chemical depolymerization treatments of these materials. Identification and quantitation of the major functional moieties in cutin and suberin have been accomplished with cross-polarization magic-angle spinning as well as direct polarization methods. Evidence for polyester crosslinks and details of the interactions among polyester, wax, and cell-wall components have come from a variety of spin-relaxation measurements. Structural models for these protective plant biopolymers have been evaluated in light of the NMR results. 

These results demonstrated the usefulness of 13C NMR in studies of molecular structure and dynamics for the polymeric constituents of plant cuticle. Although these materials are insoluble and sometimes present as interpenetrating phases, CPMAS and spin relaxation techniques helped identify important carbon types and provided structural clues to the protective functions of cutin and suberin in terrestrial plants. 

Cuticle. The cuticle of adult nematodes is relatively impermeable and is composed primarily of a complex of several proteins. These proteins include collagens, fibroids, elastoids, and keratoids, possibly hardened by tanning with pol3rphenols or quinones. Sometimes lipide materials are also present (8, 10y 52). When such lipide materials are present on the adult cuticle, they probably take the form of hydroxy fatty acids or esters of fatty acids with monohydroxy alcohols. Such materials may form ring compounds. Regardless of the exact chemical nature, the lipides are unquestionably one of the chief barriers to permeability. These materials are commonly difficult to demon-... 

Method. Whether to use stomatal density or stomatal index from leaf fossils for paleoelevation reconstruction depends on the availability of modern reference material and the quality of the fossil cuticle. Ideally both should be used on the same material to increase the confidence in the provided estimates. In cases, however, when the quality of the fossil cuticle does not allow epidermal cells to be recognized with the necessary accuracy, and stomatal index can not be determined, stomatal density measurements are the only available option. To use stomatal index, a training set of modem and herbarium material grown under different C02 pressure provides the necessary calibration. Because stomatal density is influenced by more factors than just the C02 partial pressure, the actual response of stomatal density of the chosen fossil taxon has to be confirmed by analyzing leaves from actual elevation transects. Stomatal density is physiologically more informative than stomatal index as SD is strongly related to maximum stomatal conductance. 

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