Figure 3.

Possible up-regulation of slowly activating vacuolar currents by cytosolic Mg²⁺ in fava bean guard cells. Whole-vacuole currents measured from one vacuole at different Mg²⁺ concentrations in the bath solution. The holding potential was −40 mV with an interval time between pulses of 1 s. Standard bath and pipette solutions (see “Materials and Methods”) were used with varying Mg²⁺ concentrations (0, 1, and 5 mm) in the bath. Note that 10 μm CaCl was added to the bath solution. A, Current recordings started in a bath solution containing no added Mg²⁺. B and C, Bath solutions containing 1 mm (B) and 5 mm Mg²⁺ (C) were subsequently added by local perfusion (see “Materials and Methods”). D and E, The vacuole was then perfused with a bath solution containing no added Mg²⁺. Similar experiments were repeated on eight vacuoles.