The relation of cycling of intracellular pH to mitosis in the acellular slime mould Physarum polycephalum.

The relation between intracellular pH and the mitotic cycle of Physarum polycephalum was studied by two-independent techniques. Both techniques revealed a long term cycling of intracellular pH which has the same period as the mitotic cycle, Qualitative detection of the changes in intracellular pH was made by measuring the changes in fluorescence of 4-methylesculetin which had been absorbed by the plasmodium. Quantitative measurements of intracellular pH were made throughout the mitotic cycle with antimony micro pH electrodes. The cycle of intracellular pH is sinusoidal in appearance. The maximum intracellular pH (pH 6.6) occurred at, or very near to, mitosis, and was approximately 0.6 pH units higher than the minimum pH, which occurred near the middle of the mitotic cycle.