Changes in cell wall polysaccharides and monosaccharides during development and ripening of Japanese pear fruit1

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Abstract
Changes in polysaccharide and monosaccharide components in the cell wall were studied during cell division, cell enlargmement and softening in Japanese pear fruit. Wall polysaccharides were fractionated into water soluble carbohydrate, NaClO2 soluble carbohydrate, EDTA soluble carbohydrate, acid soluble hemicellulose, alkali soluble hemicellulose and cellulose. These polysaccharides were composed of glucose, uronic acid, xylose, arabinose, galactose, rhamnose, mannose and fucose. The total polysaccharide content of the cell wall per cell (DNA content basis) remained constant during the cell division period (S1). But during the pre-enlargement period (S2) it began to increase rapidly in spite of the slightness of cell enlargement. Thereafter, during the enlargement period (S3) the polysaccharides remained almost constant although the fruits enlarged dramatically, and the polysaccharides increased somewhat with ripening. The quality of the polysaccharides, however, seemed to change actively at each stage. This suggested that the extensive fruit enlargement did not require an increase in polysaccharide content, and was rather accompanied by the partial breakdown or partial interconversion of polysaccharide components already present. The loss of arabinose and galactose in acid soluble hemicellulose was prominant in fruit softening occurring in the ripening stage. The cellulose component decreased with overripening. Water soluble pectin increased parallel to the increase in total pectin with ripening. On the other hand, xylose and non-cellulosic glucose residues did not alter with ripening or overripening. Non-cellulosic glucose continued to accumulate during cell enlargement.