Figure 8.

Whole-cell plasma membrane currents in protoplasts derived from Arabidopsis leaf mesophyll tissue in control (Na⁺-free) conditions (A–D) and in 50 mm extracellular Na⁺ solution (E–H). A, Typical currents (recorded from the same protoplast) in 10 mm (top) and 0.1 mm (bottom) extracellular Ca²⁺ in control solution. B to D, Mean ± se I-V relationships (n = 4–11) for total (B), instantaneous (C), and time-dependent (D) currents measured at 0.1, 1, and 10 mm extracellular Ca²⁺ in Na⁺-free solution. E, Typical currents (recorded from the same protoplast) in 10 mm (top) and 0.1 mm (bottom) extracellular Ca²⁺ with 50 mm Na⁺ present in the bath. F to H, Mean I-V relationships (n = 5–6) for total (F), instantaneous (G), and time-dependent (H) currents measured at 0.1, 1, and 10 mm extracellular Ca²⁺ in the presence of 50 mm Na⁺ in the bath. Time-dependent currents were calculated as described in “Materials and Methods.” PS contained 50 mm potassium gluconate and 30 mm KCl. Extracellular K⁺ was 0.1 mm throughout. All concentrations are given in mm.