Morphology and Chemical Composition of Barley Endosperm Cell Walls

Cell walls have been isolated from barley endosperm and found to contain a microfibrillar phase which is embedded in an amorphous matrix. The microfibrillar phase probably consists of cellulose, together with tightly bound arabinoxylan and polysaccharides rich in mannose. The matrix material is arabinoxylan (approx. 25%) and β-glucan (approx. 75%). Pectic polysaccharides are absent from the isolated cell walls. After successive removal of the matrix polysaccharides with water and 1-M NaOH, only 6% of the wall remains. The intra-cellular surfaces of the wall fragments are extensively pitted, probably as a result of adpression of starch granules into the cell wall material during endosperm development. Although polysaccharides are the major components of the cell walls, some nitrogen (less than 1%) is present. Phenolic compounds may also be wall constituents, but hydroxyproline could not be detected.