Figure 1.
APK1b promoter direct GUS expression to the guard cells.
GUS histochemical localisation of expression directed by the APK1b upstream gene promoter in leaves of 3 week old seedlings. Scale bar = 50 µm.
Figure 2.
Stomatal conductances of apk1b-1 are lower than control plants.
Mean stomatal conductances of apk1b-1 plant leaves compared to Col-0 control leaves. A: Leaves of plants exposed to saturating light for 30 min, then exposed to darkness, arrow indicates when light was switched off. B: Leaves exposed to increasing light intensities ranging from 0 to 2000 µmol photon m−2 s−1. C: Leaves of plants exposed to red light for 60 min, then exposed to blue and red light, arrow indicates when blue light was switched on. Error bars represent the standard error. Values were statistically tested using unpaired t-tests and significant differences from Col-0 control are indicated (* = p<0.05, ** = p<0.01).
Figure 3.
Stomatal density and index of apk1b-1and apk1b-2 are similar to those of control plants.
A: Stomatal density and B: stomatal index were calculated from the abaxial surface of fully expanded leaves. Error bars represent the standard error.
Figure 4.
Stomata of plants lacking APK1b cannot open as wide in response to light but can close in response to ABA or CO2.
The effect of A: light, B: ABA and C: CO2 on stomatal aperture measurements from apk1b-1, apk1b-2 and control plants. Apertures were measured from detached leaf abaxial peels following treatment with stimuli as indicated. For the response to light shown in A. plants were dark-adapted and peels prepared in dim light at the start of the experiment. Significant differences from Col-0 control are indicated (* = p<0.05).
Figure 5.
apk1b-1 and apk1b-2 have reduced levels of transpiration and increased relative water content in comparison to control plants.
A: Temperature of the leaf surface following drought imposition for the time indicated was measured by infra-red thermography. The onset of watering is indicated by an arrow. Significant differences are indicated (* = p<0.05). B: Relative water content was calculated from measurements of well-watered plants and plants subjected to 7 days of drought. Letters indicate significance groups (p<0.05).