Membrane potential and resistance, each of which was the sum of those of the plasmalemma and tonoplast, measured in the coenocytic thallus ofBoergesenia forbesiiwere 6.7 mv inside positive and 2.8 kΩ.cm2, respectively.Protoplasm squeezed from the thallus into artificial sea water (ASW) formed numerous spherical bodies, which are termed aplanospore-like cells (simply“spores”). The following electrical properties of the“spores”20–40 hr after squeezing were obtained: potential difference (p.d.) across plasmalemma (Eco) was−66 mv (−means inside negative), plasmalemma resistance 665Ωcm2, p.d. across the tonoplast (Evc)+73 mv, and tonoplast resistance 2.6 kΩ.cm2. Tenfold increase in external K+ caused+45 mv change inEcoand+17 mv inEvc. The plasmalemma was entirely depolarized in Ca++-free ASW or ASW containing Triton X-100.When the“spore”was immersed in potassium-rich (277 mil) ASW,Ecowas almost zero and the tonoplast showed two states (I and II,Eveabout+70 mv and+20 mv, respectively).Evcwent back and forth between the two states spontaneously or when a small current was applied. In most cases oscillatory changes inEvcoccurred after the lapse of a long time in the K+-rich sea water. Membrane resistances in states I and II were 5 and 9
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