Figure 5.

Voltage-dependent single-channel anion currents across the plasma membrane of DTZ-derived protoplasts as measured in the whole-cell configuration. Anion channels were activated by Al treatment of roots from the Al-resistant cv ATP-Y prior to protoplast preparation. The pipette solution contained 100 mm TEACl, 2 mm MgCl₂, 2 mm MgATP, 2 mm EGTA, and 10 mm HEPES/Tris (pH 7.2), and the bath solution contained 20 mm TEACl, 1 mm CaCl₂, 0.05 mm AlCl₃, and 5 mm MES/Tris (pH 4.3). a, Steady-state channel fluctuations at voltages indicated. o_i indicates open states, and c the closed state or open state for additional active channels. b, Corresponding current-voltage curves in the presence of standard solutions (n = 7). The straight line represents a linear fit to inward current amplitudes between −132 and −52 mV. The voltage-dependent rectification of the current-voltage curve reverses direction near the Nernst potential for chloride (arrow).