Reversible inhibition of cytoplasmic streaming by intracellular Ca2+ in tonoplast-free cells ofChara australis

Summary The effect of the intracellular concentration of Ca²⁺ on the cytoplasmic streaming of tonoplast-free cells ofChara australis was studied by intracellular perfusion. The perfusion media contained 1 mM Mg · ATP. Both cell ends were cut and left open. Media of different Ca²⁺ concentrations were perfused through the cell and the rate of the cytoplasmic streaming just after perfusion was measured. The critical concentration of Ca²⁺ for inhibiting the streaming was 5 × 10^–4M, which was substantially higher than that found earlier byWilliamson (1975) andHayama et al. (1979). Recovery from the inhibition occurred, though not completely, by removing Ca²⁺.In tonoplast-free cells the Ca²⁺ sensitivity differed according to the culture conditions. Cells cultured indoors exhibited a higher sensitivity than those cultured outdoors. Theformer cells contained granule-rich endoplasm aggregates after loss of the tonoplast, while the latter cells did no such aggregates. The aggregates were fixed to the cortical gel with a high dosage of Ca²⁺ and freed by removing it.