Plant cell walls constitute the key structural components of plants and many plant‐based foods. They are well known for contributing to a range of “quality” characteristics, from organoleptic texture to the properties of dietary fiber. Much of the research on cell walls has focused on the physiological aspects of plant growth and development with the belief that this route holds the key to controlling quality characteristics. In addition, consideration of quality has often been determined by what is easily measurable. This review assesses critically the role of plant cell walls in relation to the ultimate determinant of quality – the consumer, but within a whole food‐chain context. We conclude that effective exploitation of cell‐wall research in relation to optimizing quality requires an integrated approach taking into account the multi‐functional roles of plant cell walls, and the diversity of consumer‐related quality dimensions.
The mechanical properties of plant organs depend upon anatomical structure, cell-cell adhesion, cell turgidity, and the mechanical properties of their cell walls. By testing the mechanical responses of Arabidopsis mutants, it is possible to deduce the contribution that polymers of the cell wall make to organ strength. We developed a method to measure the tensile parameters of the expanded regions of turgid or plasmolyzed dark-grown Arabidopsis hypocotyls and applied it to the fucose biosynthesis mutant mur1, the xyloglucan glycosyltransferase mutants mur2 and mur3, and the katanin mutant bot1. Hypocotyls from plants grown in the presence of increasing concentrations of dichlorobenzonitrile, an inhibitor of cellulose synthesis, were considerably weakened, indicating the validity of our approach. In order of decreasing strength, the hypocotyls of mur2 Ͼ bot1 and mur1 Ͼ mur3 were each found to have reduced strength and a proportionate reduction in modulus compared with wild type. The tensile properties of the hypocotyls and of the inflorescence stems of mur1 were rescued by growth in the presence of high concentrations of borate, which is known to cross-link the pectic component rhamnogalacturonan II. From comparison of the mechanical responses of mur2 and mur3, we deduce that galactosecontaining side chains of xyloglucan make a major contribution to overall wall strength, whereas xyloglucan fucosylation plays a comparatively minor role. We conclude that borate-complexed rhamnogalacturonan II and galactosylated xyloglucan contribute to the tensile strength of cell walls.Cell walls constrain the rate of plant cell expansion during growth and limit the final size that plant cells achieve by resisting tensile stresses generated within the wall as a consequence of turgor pressure within the cell (Carpita, 1985; Cosgrove, 2000; Darley et al., 2001). There are two major polysaccharidic structural networks in the walls of dicotyledonous plants: the cellulose network tethered by cross-linking glycans and the pectin network (McCann and Roberts, 1991; Carpita and Gibeaut, 1993). The cellulose network dominates the mechanical response of isolated cell walls in small deformation rheology measurements (Whitney et al., 1999), but the manner in which the cellulose is deposited is conditioned by the presence of other molecules, leading to gross mechanical differences (Whitney et al., 1995(Whitney et al., , 1999 Chanliaud and Gidley, 1999; Chanliaud et al., 2002). In work with onion (Allium cepa), a non-graminaceous monocot with a cell wall composition typical of a dicotyledon (Redgwell and Selvendran, 1986), Wilson et al. (2000) obtained evidence for the independence of the cellulose and pectin networks in the epidermis and showed that pectin is mechanically important in its own right as well as affecting the viscoelastic properties of the cell wall through its modification of cellulose hydration. However, the specific structural features of cell wall polysaccharides that influence mechanical properties have not been identified...
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