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The high pH state of Chara plasmalemma (Bisson, M.A., Walker, N.A. 1980. J. Membrane Biol. 56:1–7) was investigated to obtain detailed current-voltage (I/V) and conductance-voltage (G/V) characteristics in the pH range 7.5 to 12. The resting conductance started to increase at a pH as low as 8.5, doubling at pH 9.5, but the most notable increases occurred(More)
Salinity, together with light, temperature, and nutrients, is one of the abiotic factors affecting algal growth and distribution. Changes in salinity result in immediate water fluxes according to the osmotic gradients. This rapid response is followed by osmotic acclimation through adjustment of the cellular solute concentrations. As a result of these(More)
Removal of Ca2+ from the medium results in depolarization of theChara internodal cell and an increase in membrane conductance (G m). The increase in conductance is associated with an increase in K+ conductance, as judged by Ca2+ effects on the K+ dependence of clamp current. The voltage dependence ofG m is also affected by Ca2+, as is the time course of the(More)
Codium decorticatum maintains its internal osmotic pressure 2.3 bar above the osmotic pressure of the external medium, which results in a hydrostatic pressure difference (turgor) of 2.3 bar. During hypoosmotic stress the primary mechanism for decreasing the internal osmotic pressure is a decrease in active Cl− influx. The decreased Cl− influx is accompanied(More)
Ventricaria ventricosa and its relatives have intrigued cell biologists and electrophysiologists for over a hundred years. Historically, electrophysiologists have regarded V. ventricosa as a large single plant cell with unusual characteristics including a small and positive vacuole-to-outside membrane potential difference. However, V. ventricosa has a(More)
Above a critical external pH (about 10.5), theChara membrane acquires new propertes. In this state the membrane potential is close to the equilibrium potentials for H+ and OH−, hyperpolarizing as external pH increases with a slope of −59 mV/pH unit. The membrane conductance increases by an average factor of 2.4 above the critical pH. These changes are(More)
The time course of hypertonic and hypotonic turgor regulation was studied in Ventricaria (Valonia) using pressure probe and I/V(current-voltage) analysis. Of 11 cells, 9 exhibited hypertonic turgor regulation, ranging from 100% regulation in 150 min to 14% regulation (14% recovery of the decrease in turgor) in 314 min. Some cells began regulating(More)
Reported inhibitors of the Characean plasmalemma proton pump were tested for their ability to inhibit the passive H(+) conductance which develops in Chara corallina Klein ex Willd. at high pH. Diethylstilbestrol inhibits the proton pump and the passive H(+) conductance with about the same time course, at concentrations that have no effect on cytoplasmic(More)
The current-voltage (I/V) profiles of Ventricaria (formerly Valonia) membranes were measured at a range of external potassium concentrations, [K+] o , from 0.1 to 100 mm. The conductance-voltage (G/V) characteristics were computed to facilitate better resolution of the profile change with time after exposure to different [K+] o . The resistance-voltage(More)