Figure 9.

The level of DHAR expression determines guard cell responsiveness in response to a chronic exposure to ozone. The stomatal aperture (width/length), percent of stomata that were open (defined as having a width greater than 1 μm), and the total stomatal area per 100 stomata were determined from the abaxial epidermis of fully expanded control (C), DHAR-OX (OX), and DHAR-KD (KD) tobacco leaves prior to and after 30 d of exposure to 100 ppb ozone for 4 h/d. The width and length of at least 30 stomatal apertures were measured and used to determine the stomatal aperture (width/length) with the sd indicated. The total stomatal open area was calculated from the average stomatal aperture area and percent of stomata that were open, and reported as the total area (μm²) per 100 stomata.