The cell walls ofEragrostis tef: variations in chemical composition and digestibility

Abstract

SUMMARYTeff(Eragrostis tef)was cut at various stages of growth and divided into leaf, stem (including leaf sheath) and inflorescence. Cell walls were isolated from the leaf and stem fractions and their composition determined. Acetyl groups and individual sugars were determined by gas-liquid chromatography.Recoveries of cell walls from the same fresh weight of leaves or stems were similar at each stage of growth, but increased with maturity.Throughout the growing season the leaf cell walls differed in composition from those of the stem. At the start of growth the leaves had a lower content of xylose and acetyl groups but were otherwise similar to the stems. However, with increasing maturity and the production of a flowering stem the stem cell wall composition changed much more than that of the leaf cell walls, with a marked decrease in the content of arabinose and an increase in the content of lignin and acetyl. Over the same period the leaf cell walls showed a smaller increase in acetyl content and decrease in arabinose and uronic acid, but were otherwise unchanged.Digestion of the cell walls with a fungal cellulase preparation showed that although the two cell wall types were equally degradable while the grass was in the vegetative state, the digestibility of the stem cell walls decreased well below that of the leaves with the onset of maturity and the production of a flowering stem. This was confirmed byin vivoincubations of the cell walls in nylon bags.