Gramineae hemicelluloses

There have been many articles on the hemicelluloses,1-17 and this one, on the hemicelluloses of the Gramineae (grasses and cereals), is written in the knowledge that, when it is completed, Norman s state-... 

The malleable term hemicellulose in the title of this Chapter refers to all of the types of polysaccharide in the Gramineae, other than celluloses, starches, and fructans. The term implies nothing concerning the nature of the polysaccharides, their biological role, or their location in the plants. 

The Chapter by Wilkie (Aberdeen) on the hemicelluloses of the Gramineae serves to illustrate that not all areas of complex carbohydrates are yet amenable to neat and clear-cut structural interpretations as a result of modern technology. The article emphasizes the need for continued caution in attribution of precise structures to this enigmatic class of polysaccharides, and final answers can not yet be written on their structures and roles. 

Chemically, about 35-55% of the dry material is the glucose polymer cellulose, much of which is in a crystalline structure while another 25—35% is hemicellulose, an amorphous polymer. The remainder is mostly lignin plus less amounts of minerals, waxes, and other compounds [3]. Cellulose is formed by beta-[l, 4] glucosyl linkages in a linear backbone, whereas hemicelluloses are branched polymers composed of several monosaccharides [5]. Fig. 1 shows the schematic illustration of the cellulose chain, while Fig. 2 shows the schematic illustration of xylans from Gramineae [5, 6]. 

---