MEASUREMENTS OF THE INTRACELLULAR pH IN A SINGLE CELL OF NITELLA FLEXILIS BY MEANS OF MICRO-GLASS pH ELECTRODES

Abstract

The authors constructed micro-glass pH electrodes about 60-80 [mu] in diameter and 4-9 mm long, and the electrode characteristics and applicability to intracellular pH measurements were studied. Paired with a KCl-filled micropipette leading to a reference electrode, the micro-glass pH electrode gave an electromotive force per pH unit which closely satisfied the theoretical requirement of the Nernst equation. Tested for a standard buffer of known pH, this micro-glass pH electrode gave pH readings as reproducible as those of a large glass pH electrode; thus the standard deviation of mean 10 consecutive measurements was 0.005 pH for both electrodes. This micro-glass pH electrode was applied to the intracellular pH measurement of the sap of a single cell of N. flexilis, a fresh water alga. Stable intracellular pH recordings were obtained with minute fluctuations less than 2 mV (0.04 pH) for a period of at least 30 minutes, during which a normal plasma streaming continued around the electrode and up to the very edge of the cut end. The mean pH of the sap was 5.6 at 20[degree]C for a lot obtained from a pond in Nov., a good agreement with a previous measurement by Irwin (1923, 1930). From 2 consecutive measurements in the same cell, it was concluded that a single pH measure-, ment in Nitella gave a pH reading which was reproducible with errors of less than 0.1 pH.