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This paper investigates the impact of increased salinity on touch-induced receptor and action potentials of Chara internodal cells. We resolved underlying changes in ion transport by current/voltage analysis. In a saline medium with a low Ca(2+) ion concentration [(Ca(2+))(ext)], the cell background conductance significantly increased and proton pump(More)
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)
The electrophysiological properties of cytoplasm-rich fragments (single membrane samples) prepared from internodal cells of Chara corallina were explored in conjunction with K(+)-sensitive microelectrode and current-voltage (I-V) measurements. This system eliminated the problem of the inaccessible cytoplasmic layer, while preserving many of the electrical(More)
We have obtained and modeled the electrical characteristics of the plasma membrane of Chara internodal cells: intact, without turgor and perfused with and without ATP. The cells were voltage and space-clamped to obtain the I/V (current-voltage) and G/V (conductance-voltage) profiles of the cell membrane. The intact cells yielded similar I/V characteristics(More)
Lamprothamnium is a salt-tolerant charophyte that inhabits a broad range of saline environments. The electrical characteristics of Lamprothamnium cell membranes were modeled in environments of different salinity: full seawater (SW), 0.5 SW, 0.4 SW, and 0.2 SW. The cells were voltage-clamped to obtain the I/V (current-voltage) and G/V (conductance-voltage)(More)
The dependence of the Ca++-activated Cl- channels on potential difference (PD) was extracted from current-voltage (I/V) profiles recorded at the time of hypotonic regulation while the large conductance (G) K+ channels were blocked by tetraethylammonium (TEA). The total clamp current (I) was dominated by the Cl- I, i(Cl), with small contribution from the(More)
It is generally agreed that solute transport across the Chara plasma membrane is energized by a proton electrochemical gradient maintained by an H(+)-extruding ATPase. Nonetheless, as deduced from steady-state current-voltage (I-V) measurements, the kinetic and thermodynamic constraints on H(+)-ATPase function remain in dispute. Uncertainties necessarily(More)
We have studied fluctuations in membrane PD in Chara australis at frequencies between 1 and 500 mHz, by classical noise analysis and by inspection of the PD time-course. The former shows (1) a quasi-Lorentzian (1/f (2)) rise of noise power as frequency falls, and (2) a marked increase in noise power when the cell is exposed to high salinity (Chara australis(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)