Hemicelluloses interconnections

The cell walls are composed of microfibrils interconnected by hemicelluloses. Other polymers such as pectin and lignin fill up the space between cellulosic microfibrils and hemicelluloses. Cells are connected to neighboring cells by middle lamellae, the thin lignin-rich outermost layer of the cell wall (Taherzadeh and Jeihanipour, 2012). The primary cell wall is the outer layer containing cellulose microfibrils arranged in random. The secondary cell wall is differentiated into outer (SI), middle (S2), and inner (S3) layers (Figure 3.1). The thickness of each layer differs, but the S2 layer is the thickest and constitutes the major part of the plant cell wall (Taherzadeh... 

There are four major types of polymers in the primary cell walls of dicots hydroxyproline-rich glycoprotein, cellulose, hemicellulose and pectic polysaccharides. The mole percents of these polymers in suspension-cultured sycamore cell walls is presented in Table 8 (45, 75). The pectic polysaccharides are covalently interconnected. The hemicelluloses are non-covalently bonded to the cellulose fibers. There is no known attachment between the hydroxyproline-rich glycoprotein and the other cell wall polymers. The extent of covalent attachment between the hemicelluloses and the pectic polysaccharides is unknown. The fact that removal of the xyloglucans from the cell walls is enhanced by solubilization of the pectic polysaccharides (31, 75, 123) suggests that... 

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