Rapid Measurement of Diffusion of Gas Through the Skin of Apple Fruits

A method was devised for measuring the resistance to gaseous diffusion of bulky plant organs, such as apple (Malus domestica Borkh.) fruits, in which the skin is the major barrier to diffusion. An individual fruit was incubated in a sealed container in the presence of a measured concentration of ethane for a certain time (usually 20 min). The fruit was then transferred to another, similar container. The ethane concentration that diffused into the new container was measured after an equal time (usually 20 min). An expression relating resistance to the measured ethane concentrations was derived from Fick's First Law of diffusion. An estimate of the internal volume of the fruit, accessible to ethane, was also necessary. The method was tested on several fruits of various apple cultivars. Longer incubation periods are necessary for apples with high diffusive resistance.