نمونه متن انگلیسی مقاله
Polysaccharide-rich plant cell walls are important biomaterials that underpin plant growth, are major repositories for photosynthetically accumulated carbon, and, in addition, impact greatly on the human use of plants. Land plant cell walls contain in the region of a dozen major polysaccharide structures that are mostly encompassed by cellulose, hemicelluloses, and pectic polysaccharides. During the evolution of land plants, polysaccharide diversification appears to have largely involved structural elaboration and diversification within these polysaccharide groups. Cell wall chemistry is well advanced and a current phase of cell wall science is aimed at placing the complex polysaccharide chemistry in cellular contexts and developing a detailed understanding of cell wall biology. Imaging cell wall glycomes is a challenging area but recent developments in the establishment of cell wall molecular probe panels and their use in high throughput procedures are leading to rapid advances in the molecular understanding of the spatial heterogeneity of individual cell walls and also cell wall differences at taxonomic levels. The challenge now is to integrate this knowledge of cell wall heterogeneity with an understanding of the molecular and physiological mechanisms that underpin cell wall properties and functions.
Growing plant organs have the strength and flexibility to resist the impacts of rain and intense gusts of winds and also the capability of penetrating compacted soils. The mechanical robustness of plant organs is due to the presence of tough cell walls at cell surfaces. Cell walls do not only impart cell shapes and mechanical properties for extension growth in variable environments, but are also responsible for cell-to-cell adhesion that is a core attribute of the mechanical robustness of growing plants. The importance of plant cell walls extends into many areas of human activity and endeavor. Cell walls are an important set of biomaterials in that they are not only crucial for the properties of plant organs and hence crop growth, but they are in addition the major repository for the Earth’s photosynthetically fixed carbon and a crucial resource in carbon recycling. Cell walls are therefore critical to plant and microbial growth, herbivore nutrition, and to the maintenance of terrestrial and marine ecosystems. Moreover, cell walls are widely exploited in diverse human activities relating to food, food additives, industrial enzymology, fibers, textiles, paper, lumber, and biofuels. This wide reach of issues pertaining to cell walls and their components places them with a central importance in biology (Albersheim et al., 2010). Cell walls have long been classed as primary or secondary, depending upon whether they are, respectively, extendable or non-extendable during organ growth. Primary cell walls generate turgor pressure (thus resisting tensile forces), accommodate cell expansion, mediate cell adhesion, and occur at the surface of most plant cells. Secondary cell walls are restricted to specific sets of differentiated cells, tend to be thicker than primary walls, and resist compressive forces. As we learn about the microstructures of cell walls, we can see that there is a great variety of both primary and secondary cell walls in molecular terms and also that there may not be clear boundaries between the architectures and properties of the two types of wall, but more of a continuum (Albersheim et al., 2010; Knox, 2008).