Analysis of Cross-Links in the Growing Cell Walls of Higher Plants

Abstract

The growing cell walls of higher plants consist of a rather small number of major polymers (Table 1; for details, see Fry 1988). Most of these are polysaccharides, which fall into three major classes: cellulose [β-(1→4)-glucan, the skeletal frame-work of the wall] hemicelluloses (generally rigid, rod-shaped polysaccharides that hydrogen-bond to the cellulose and can be extracted from the wall with cold NaOH), and pectins (jelly-like, often acidic polysaccharides that are more loosely bound in the wall; a proportion can be extracted with chelating agents). In the growing cell walls of Dicotyledons, these three classes are about equally abundant, whereas grasses possess much less pectin (McNeil et al. 1984). All growing cell walls also contain some glycoproteins (Lamport 1977), and some contain large amounts of additional polymers - e.g., even rapidly growing epidermal walls contain cutin (Lendzian and Schönherr 1983), which is built up of a polyester of long aliphatic chains mixed, meshed or bonded with a network of phenolic rings (Holloway 1982).