Cell Wall Metabolism in Growing and Ripening Stone Fruits

The time-course changes of the composition of the cold watersoluble, the hot water soluble, the ammonium oxalate soluble,the 4% KOH soluble, the 24% KOH soluble and the 24% KOH insolublecell wall fractions, as well as of the activities of ß-D-xylosidase,-D-mannosidase, ß-D-galactosidase and ß-D-glucosidase,were monitored during growth and ripening of the fleshy pericarpof wild plums, peaches and apricots. All fractions increased up to a peak, which occurred beforethe onset of ripening. During ripening the pectic fractionswere extensively decreased, the hemicellulosic fractions wererestrictively decreased, while the crude cellulosic fractionwas not affected, being always present in greater amounts incomparison to the previous mentioned fractions during all phasesof fruit development. The relative changes of the two pecticfractions and the two hemicellulosic ones indicate conversionof the more soluble fractions to the less soluble ones duringgrowth and the reverse conversion during ripening. The coldwater soluble fraction appeared only during ripening and itschanges were closely related to the extensive breakdown of pecticfractions during ripening. The enzymic activities were not foundduring growth. They appeared at the begining of ripening (apricots)or a little earlier and followed a concrete pattern of changes. (Received November 30, 1991; Accepted August 3, 1992)