Studies on wheat endosperm i. Chemical composition and ultrastructure of the cell walls

Abstract

A method is described for the isolation of wheat endosperm cell walls free from non-endospermic cell walls in a 70 % ethanol medium which prevents the loss of watersoluble polymeric components. The isolated walls have been fractionated by successive extractions with water, 0-05M EDTA, 4-27M KOH, and4.38MNaOH containingO.81M H3B03-The cell walls, as isolated, contain 14-15% protein and 75% polysaccharide, 85 % of which is arabinoxylan, whilst the remainder consists of equal amounts of fJglucan and fJ-glucomannan. Walls prepared from Insignia, Olympic, and Wren wheat flours were very similar, both with respect to the proportions of the polymeric components and to the monosaccharide composition of the walls and wall fractions. The appearance of endosperm cell walls in situ and in wall isolates was examined by light microscopy, scanning and transmission electron microscopy, and a technique is described for the scanning electron microscopy of walls in endosperm sections. Scanning electron micrographs show the apparent moulding of the walls on the cell contents and the different fracture patterns of prismatic and central cells. The cell walls have a microfibrillar skeleton embedded in the amorphous matrix components. © 1973, CSIRO. All rights reserved.