EFFECT OF CHILLING INJURY ON PHYSICOCHEMICAL PROPERTIES OF PERSIMMON CELL-WALLS

The chemical composition and physical properties of cell wall polysaccharides of persimmon fruit were determined at harvest, and after three weeks at 20-degrees, eight weeks at 0-degrees, and eight weeks at 0-degrees followed by three days at 20-degrees. When fruit ripened normally (three weeks, 20-degrees) cell wall pectic polysaccharides were solubilized and arabinose and galactose were lost from the cell wall material (CWM). Fruit ripened after storage at 0-degrees developed severe chilling injury and underwent many changes similar to those of the ripe fruit. However, these changes occurred more rapidly and were more extensive. In this case, the solubilized pectic polymers possessed a higher M(r) and contained a higher proportion of neutral sugars than those solubilized during normal ripening. Glucose and xylose, sugars normally associated with hemicellulosic polysaccharides, were lost from the CWM of the chilling injured fruit but not from normally ripened fruit. None of the above changes occurred during storage at 0-degrees, but a net increase in the amount of CWM during this time suggested synthesis of cell wall constituents was occurring. The cell walls of chilling injured persimmon fruit therefore underwent dramatic changes, some of which were characteristically different from those displayed by fruit allowed to ripen normally.