Molecular associations between wall polymers

The organization of walls can be described as consisting of cellulosic microfibrils and struc­tural proteins inserted into and reinforcing a multicomponent gel matrix, composed of stereo-irregular, non-cellulosic heteropolysaccharides (heteroglucans, heteromannans, het — eroxylans, (1^3,1^4)-p-D-glucans, and pectins). In primary walls these matrix polysac­charides may interact through physical associations with one another and the cellulosic microfibrils and also through covalent associations. In secondary walls the matrix polysac­charides also interact covalently with non-carbohydrate wall components such as lignins, suberin, cutin, cutan, and proteins. The following sections describe the nature of both non-covalent and covalent associations between wall polymers.