Electron-microprobe analysis of apple fruit tissues affected with bitter pit

The concentrations of the mineral elements K, Ca, Mg, P, S and Cl were compared in pitted and sound tissues of mature fruits of the apple cultivars ‘Akane’, ‘Reine des Reinettes’ and ‘Idared’ using an electron microprobe. Mg, Ca and to a lesser extent S were always present in higher concentrations in pitted areas than in non-pitted ones, in the ratio of 3.0 to 14.4 for Mg and 3.1 to 7.9 for Ca. The K concentration in pitted tissues was variable showing no significant difference in ‘Akane’, and an increase or decrease in ‘Reine des Reinettes’ and ‘Idared’, respectively. P and Cl concentrations were also variable. Serious perturbations were found in the ionic content of the pitted tissues affecting several elements implicated in essential physiological processes.