抄録
Cyclic changes in the pH of the slime layer on the surface of the Physarum plasmodium (surface pH) were measured, with special reference to the contraction-relaxation cycle. Measurements were made with a specially designed small antimony electrode. The oscillation detected was confirmed by spectrophotometry with a pH indicator dye (bromcresol purple). A clear cor-relation was found between cyclic changes in the surface pH of a plasmodial strand segment and the contraction-relaxation cycle. The surface pH oscillated with the same period but in opposite phase to the cyclic tensile force pro-duction, as does the cytoplasmic pH. The peak-to-peak amplitude of the oscillation usually was of the order of a 0.1 pH unit or less. No stretch acti-vation was found with the pH oscillation.
