Changes in the composition of cotton fibre cell walls during development.

Purified cell walls, prepared from cotton fibres (Gossypium arboreum L.) at different growth stages, were subjected to successive extractions to give pectic, hemicellulosic, and α-cellulosic fractions. The protein content and sugars obtained after hydrolysis of the total cell walls and of the various fractions were quantitatively estimated. The amount of protein in the fibre cell walls from one ovule reached a maximum value at the end of the elongation growth, decreased, and then reached a second maximum at the end of the secondary wall deposition. The absolute amounts of fucose, galactose, mannose, rhamnose, arabinose, uronic acid, and non-cellulosic glucose residues all reached a maximum at the end of the primary wall formation or at the beginning of the secondary wall formation. Only the absolute amounts of xylose and of the cellulosic glucose residues increased until the end of the fibre development. Most conspicuous was the decrease in the absolute amounts of non-cellulosic glucose and of arabinose residues during the secondary wall formation, possibly indicating a turnover of at least some of the hemicellulosic wall material.