Fig. 2.

Malate activation of anion currents in Arabidopsis thaliana wild-type (WT) guard cells occurs at a buffered resting cytosolic free Ca²⁺ concentration of 0.2 μM, and malate activation of S-type anion channel currents is enhanced by 2 μM free Ca²⁺ compared with 0.2 μM free Ca²⁺ in the pipette solution. (a) Typical whole-cell recordings of S-type anion channel currents in guard cell protoplasts of wild type plants with 0.2 μM free Ca²⁺, 2 μM free Ca²⁺, 0.2 μM free Ca²⁺ + 1 mM malate and 2 μM free Ca²⁺+1 mM malate in the pipette solution. (b) Steady state current-voltage relationships recorded as in (a). The number of guard cells was n = 5–7 for each condition. Data are mean ± SE (P < 0.01 for 0.2 μM free Ca²⁺ vs 0.2 μM free Ca²⁺ + 1 mM malate; P < 0.01 for 2 μM free Ca²⁺ vs 2 μM free Ca²⁺ + 1 mM malate at −145 mV).