Figure 1.

Stomatal responses of tdt plants following different stimuli. A to C, Stomatal opening and closing kinetics in response to light and CO₂ concentrations. g_s was evaluated in tdt-1 and tdt-2 and the wild type (WT) in response to light (A), dark (B), and CO₂ levels (C). Data presented are means ± se (n = 10). D, Stomatal aperture after incubation with ABA, malate, fumarate, and citrate. The totally expanded fifth leaf of 4-week-old plants was floated on stomatal opening buffer containing 10 mm KCl, 50 μm CaCl₂, and 5 mm MES-Tris (pH 6.15) for 2 h in the light (150 μmol m^–2 s^–1) to preopen stomata. Afterward, ABA, malate, fumarate, citrate, or ethanol (solvent control) was added to the opening buffer. After more than 2 h of incubation, the stomatal aperture was examined in the isolated epidermal fragments. Six leaves from different plants were evaluated, and the apertures of at least 20 stomata per leaf were measured, totaling at least 120 stomata per genotype. Data are means ± se (n = 6) obtained in two independent experiments with comparable results. The asterisk indicates a value that was determined by Student’s t test to be significantly different (P < 0.05) from the wild type.