Variations in morphology and composition of barley endosperm cell walls

BACKGROUND: The endosperm. cell walls (CWs) impact upon barley grain utilization as well as influence animal and human nutrition. The objective of this study was to examine the morphological and compositional differences in the endosperm CWs derived from barley grain grown in different (uncontrolled) environments in Canada, and differing in grain hardness, protein, and total beta-glucan contents. RESULTS: The endosperm CWs were isolated from barley, cv. Metcalfe, grown in Davidson, SK (sample A), Hythe, AB (sample B), and Hamiota, MB (sample C). The inner wall surfaces of sample A exhibited deep indentations made by large and small starch granules, whereas the CWs of sample B were thicker, had smooth surface, and exhibited a greater degree of binding between the adjoining cells. The CWs of sample A contained the lowest amount of beta-glucans but the highest amount of arabinoxylans and the mannose-containing (glucomannans) polysaccharides. The CWs of sample B contained the highest ratio of ferulic and dehydrodiferulate residues to Xyl residues among the samples, indicating the greatest potential and degree of cross-linking of arabinoxylans in these preparations which might be related to the strength and rigidity of the grain endosperm. The amino acid composition of the proteins detected in the isolated CW indicated the presence of 37-47 g kg(-1) of structural proteins. CONCLUSIONS: Substantial differences in the morphological appearance and chemical composition of the CW preparations were observed and some attempts were made to relate these differences to the variable composition and physical properties of barley grain as affected by the environmental factors. (c) 2008 Crown in the Right of Canada, Canadian Grain Commission. Published by John Wiley and Sons, Ltd.