Tissue permeability and membrane lipid composition of ripening banana fruits.

Abstract

Carbon dioxide and ethylene evolution began to increase rapidly after 10 and 21 h respectively when banana fruit were induced to ripen by treatment with propylene. At 36 h the soluble solids content of pulp tissue and the proportion of linolenic acid esterified to phospholipids extracted from pulp tissue increased. From 44 h onwards there was a progressive increase in pulp tissue permeability, as measured by leakage of electrolytes. The causes of the increased electrolyte leakage are discussed, with reference to the change in the proportion of linolenic acid and the increase in pulp soluble solids. INTRODUCTION Experimental evidence that the apparent permeability of banana fruit tissues increases during ripening (Sacher, 1962, 1966, 1967; Baur and Workman, 1964; Brady, O'Connell, Smydzuk, and Wade, 1970) has been criticized on the grounds that some of the measurements were affected by artefacts (Burg, Burg, and Marks, 1964; Simon, 1977). The proportion of linolenic acid esterified to membrane phospholipids increases during ripening of banana fruit (Wade and Bishop, 1978) and changes in tissue permeability might be causally associated with changes in membrane composition. This paper examines whether the change in lipid composition can be correlated with other ripening phenomena, including tissue permeability. Ripening was induced in banana fruit by applied propylene, which enables the rates of both endogenous ethylene evolution and respiration to be measured (McMurchie, McGlasson, and Eaks, 1972). Measurements were made of respiration rate, ethylene evolution, soluble solids content, tissue permeability, and fatty acid This content downloaded from 157.55.39.10 on Mon, 08 Aug 2016 04:35:33 UTC All use subject to http://about.jstor.org/terms 976 Wade, Campbell, and Bishop—Permeability of Ripening Bananas composition of extracted phospholipids. The times at which each of these parameters changed significantly were determined. This method measures only gross changes in the bulk tissue and success in detecting the beginning of a particular change depends upon the proportion of cells in which the change occurs simultaneously and the sensitivity of the measurements made. MATERIALS AND METHODS