Cessation of cytoplasmic streaming of Chara internodes during action potential

Cytoplasmic streaming of the Chara internode stops temporarily at the peak of the action potential. Use of the technique of vacuolar perfusion established that the sudden cessation of cytoplasmic streaming is caused mainly by a temporary disappearance of its motive force. Recovery of the rate of cytoplasmic streaming occurs in parallel with that of the motive force. The ‘viscosity’ of the cytoplasm remains almost unchanged during the whole period of excitation except at the peak of the action potential.