Figure 3.

The SV-type channels from Arabidopsis mesophyll cells discriminate poorly between K⁺ and Na⁺. Slowly activating outward currents were recorded from isolated tonoplast patches in response to 2.5-s voltage pulses ranging from +120 mV to −100 mV. Holding voltage between the test pulses was 0 mV. A, Current recordings from an isolated tonoplast patch with the vacuolar side of the membrane exposed to the bath solution. Replacement of the bath (vacuolar) KCl with 100 mm NaCl had only little effect on current amplitude, activation kinetics, and rectification. B, Steady-state current-voltage curves corresponding to the data in A. C, Current recordings from an isolated tonoplast patch with the inverse geometry (cytosolic side exposed to the bath). As above, current amplitudes, activation kinetics, and current-voltage characteristic (D) were largely unaffected by replacement of cytosolic KCl by NaCl. Data were filtered at 400 Hz and sampled at 1kHz. Steady-state currents were determined by averaging the last 250 ms of each current trace.