The stomatal response to CO2 is linked to changes in guard cell zeaxanthin.
by Zhu J., Talbott L. D., Jin X., Zeiger E. (1998)
J. Zhu, L. D. Talbott, X. Jin, E. Zeiger
in Plant Cell Environ. 21: 813–820. –
The mechanisms mediating CO2 sensing and light–CO2 interactions in guard cells are unknown. In growth chamber-grown Vicia faba leaves kept under constant light (500 μmol m–2 s–1) and temperature, guard cell zeaxanthin content tracked ambient [CO2] and stomatal apertures.
Increases in [CO2] from 400 to 1200 cm3 m–3 decreased zeaxanthin content from 180 to 80 mmol mol–1 Chl and decreased stomatal apertures by 7·0 μm. Changes in zeaxanthin and aperture were reversed when [CO2] was lowered.
Guard cell zeaxanthin content was linearly correlated with stomatal apertures. In the dark, the CO2-induced changes in stomatal aperture were much smaller, and guard cell zeaxanthin content did not change with chamber [CO2].
Guard cell zeaxanthin also tracked [CO2] and stomatal aperture in illuminated stomata from epidermal peels. Dithiothreitol (DTT), an inhibitor of zeaxanthin formation, eliminated CO2-induced zeaxanthin changes in guard cells from illuminated epidermal peels and reduced the stomatal CO2 response to the level observed in the dark.
These data suggest that CO2-dependent changes in the zeaxanthin content of guard cells could modulate CO2-dependent changes of stomatal apertures in the light while a zeaxanthin-independent CO2 sensing mechanism would modulate the CO2 response in the dark.