Differential alkali-extraction of hemicellulose and hydroxyproline from non-delignified cell walls of lupin hypocotyls.

The extraction by alkali of hemicellulose polysaccharides and polymer hydroxyproline from non-delignified, primary cell-walls of lupin hypocotyls has been studied, using sequential extractions at 0 degrees and 18-22 degrees. 10% Aqueous potassium hydroxide at 0 degrees rapidly removed about two-thirds of the hemicellulose normally extracted in 10% KOH at 18-22 degrees and including nearly all of the hemicellulose-A. Little hydroxyproline was released at 0 degrees. When the temperature was subsequently raised to 18-22 degrees, the remaining 10% KOH-soluble hemicellulose, along with most of the hydroxyproline, was released. The monosaccharide composition of these fractions changed markedly with the time of extraction. Arabinose increased from 35% of the polysaccharide extracted during the first hour at 18-22 degrees to similar to 65% of the polysaccharide extracted between 16 and 20 h at 18-22 degrees. Hydroxyproline changed similarly as a proportion of polymer. The implications of these and other results are discussed in relation to polysaccharide and polymer extraction without prior delignification and to models of the primary cell-wall.