Figure 2.

The pattern of ABA-induced oscillations in [Ca²⁺]_cyt correlates with the final stomatal aperture. (A) Isolated epidermis of C. communis was incubated in Mes/KCl for 3 h under conditions promoting stomatal opening and then transferred to Mes/KCl containing 10 nM ABA (hatched bar). After 1 h, the ABA concentration was increased to 1 μM (solid bar). Stomatal apertures were recorded every 5 min throughout the experiment. Values are the means of 120 measurements ± SEM. (Bar = 10 min.) (B) Fura-2-loaded guard cells of open (>6 μm) stomata of C. communis were perfused with Mes/KCl, and the resting [Ca²⁺]_cyt was determined (open bar). Subsequently, guard cells were perfused with Mes/KCl containing 10 nM ABA (hatched bar). After the characteristic oscillations in [Ca²⁺]_cyt were established, the concentration of ABA was increased to 1 μm (solid bar). A representative trace is shown. (Bar = 15 min.)