Changes in the cell wall of the pear during ripening

Abstract

The cell-wall material of the Conference pear that is insoluble in ethanol was divided into fractions by extraction with boiling water and cold alkali. Each fraction was hydrolysed and the mixture of sugars separated on a paper chromatogram and estimated colorimetrically. It is assumed that each sugar in the hydrolysis mixtures corresponded to a single polysaccharide without regard to the fraction from which it was derived, and the results were interpreted in terms of the constituent polysaccharides of the cell wall. Changes that occur in the amounts of these single-sugar polysaccharides (xylan, araban, polygalacturonic acid, galactan and cellulose) were followed during storage of the pear fruit at +15[degree] and +5[degree]. Changes in the amount of the total cell wall and the fractions into which it is conveniently divided, "pectin", "hemicellulose", "cellulose", are a reflection of separate changes in amounts of individual polysaccharides. The results indicate that the cell wall of the pear appears to be in dynamic equilibrium with the cytoplasm, and polysaccharides are both broken down and synthesized during the physiological changes which take place during ripening.