The varied nature of rhythmic fluctuations in the potentials of the cytoplasm and the membrane of plant cells

1. (1) The rhythmic fluctuations in potentials in the cells of Nitella flexilis and N. mucronata may be accompanied by alternation of action potentials and local potentials, The rhythm of alternation is usually 1 a.p.:11.p. or 1 a.p.:21.p. 2. (2) The cell membrane has a potential of the order 30-50 mV which rises under the influence of calcium ions. 3. (3) In the Response, rhythmic fluctuations in potentials may appear simultaneously in the cytoplasm and membrane. 4. (4) The value of the amplitude of the rhythmic series of a.p. of the cytoplasm reaches 50-70 mV while the value of the amplitudes of the variations in potentials of the membrane is about 5-15 mV. The number of rhythms in the cytoplasm and the membrane is for the most part identical and a fluctuation in the membrane potential corresponds to each a.p. of the cytoplasm. 5. (5) A fundamental difference in the rhythmic response of the cytoplasm and the membrane is that the variations in the potentials in the response are of opposite direction. On appearance of rhythm in the cytoplasm during the generation of an a.p. pike, the value of the potentials sharply and briefly falls on average from 109 ± 12 to 37 ± 2·5 mV. In the membrane with the onset of rhythm the value of the potentials sharply and briefly increases from 43 ± 3 to 52·5 ± 5 mV. 6. (6) The changes in the membrane potential have little influence on the direction and character of the rhytm of the potential in the cytoplasm but the diffusion and electrochemical properties of the membranes must be taken into account in analysing the electrophysiological properties of the plant cell. © 1969.