Fig. 4.

Stomatal development and movement in MKKK18 knockouts and the MKKK18-overexpressing line. (A) Stomatal development is enhanced in the MKKK18-overexpressing lines. Representative line drawings show the abaxial surface of cotyledons at day 10. Change in stomatal index and the number of guard cells (GCs) and pavement cells (PCs) per cotyledon in WT Col-0, MKKK18oe and MKKK18 knockouts. Data represent the mean ± SD (n = 300) of three independent experiments. Scale bar = 50 µm. (B) Increased stomatal aperture of mkkk18-1 and mkkk18-2 knockouts compared with the WT in standard conditions (three independent experiments, 60–80 stomatal apertures at each data point). (C) The mkkk18-1 and mkkk18-2 knockouts are insensitive to ABA- and H₂O₂-induced stomatal closure (two independent experiments, 80 stomatal apertures at each data point). MKKK18oe lines were hypersensitive to ABA-, CaCl₂- and H₂O₂-induced stomatal closure (two independent experiments, 100 stomatal apertures at each data point).