Plant cell-walls origin

Xylans are the major hemicelluloses of many plant materials, where they often contribute to the rigidity of plant cell walls. Most xylans are heteropolysaccharides with a homopolymeric backbone chain of 1,4-linked j8-D-xylo-pyranose units. The degree and t pe of substitution of the backbone is dependent on the plant origin of a xylan. In addition to xylose, xylans may contain L-arabinose, D-glucuronic acid or its 4-O-methyl ether, and acetic, p-coumaric, and ferulic acids. 

Fusinite maceral distinguished by the well-preserved original form of plant cell wall structure, intact or broken, with open or mineral-filled cell lumens (cavities). 

Plant cell walls are of vital importance to the activity of cells and are also of significance to the texture of foods originating from plant sources. This type of cell wall is mostly composed of cellulose, pectin and hemicellulose, proteins,... 

A number of polysaccharides, of microbial origin, contain nonsugar substituents, such as ketals of pyruvic acid, that are stable under the conditions of methylation analysis but are acid labile. Unless precautions are taken, such groups can easily lead to the misidentification of branchpoint residues. However, most plant cell wall polysaccharides contain noncarbohydrate substituents that are either alkali labile (e.g., 0-acetyl and phenolic esters) or stable to base and acid hydrolysis (e.g., 0-methyl ethers). The detection and location of 0-methyl ethers can be achieved by performing the methylation with deuterated methyl iodide (Ring and Selvendran, 1980 Selvendran, 1983b) or ethyl iodide. 

Darvill and Albershelm (50), Dixon and associates (51), Hadwlger and co-workers (52,53) and West (54) have reviewed the extensive literature on ellcltors responsible for the biosynthesis of phytoalexins (newly-synthesized compounds which Impart resistance). It Is now clear that ellcltors of physiological origin are soluble carbohydrates derived by enzymatic hydrolysis of either plant cell walls... 

Dietary fiber (DF) has taken on a larger meaning than its original definition of plant cell wall material resistant to the digestive process (IJ in animals or man. 

This broad understanding of dietary fiber makes it difficult to describe or characterize chemically and to elucidate its behavior in the gastrointestinal tract. Nevertheless with changing dietary habits and recommendations for food intake for good health and nutrition, it is important that the chemistry of this class of food components be more readily characterized and understood. Since much dietary fiber Is of cell wall origin, some of the approaches that have been successfully used to define and explain the chemistry of plant cell walls (5, 6) should be applicable to research on the characterization and function of dietary fiber (7, 9), To this end we have... 

The formation of cellulose fibrils in plant cell walls is associated with distinct aggregates of spherical structures in the plasmalemma, originally postulated by Preston before they were found. It is now uncertain whether these contain an appreciable part of the required glycosyltransferase, or are simply a kind of organising or spinning mechanisms for bringing cellulose molecules together to form fibrils. 

The macerals are actually identified microscopically by their form and reflectivity and are divisible into three basic groups (1) the vitrinite group—sometimes called huminite in subbituminous coals—is derived from coalified woody tissue, (2) the exinite group—sometime called liptinite—is derived from the resinous and waxy parts of plants, and (3) the inertinite group is derived from charred and biochemically altered plant cell wall material and each group has a characteristic appearance and physical characteristics (Tables 4.7 and 4.8) (ICCP, 1963). The three groups are each further subdivided on the basis of individual maceral form, which is due in no small part to their mode of origin (Table 4.9) (Murchison et al., 1985). 

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