The stomatal response to CO2 is linked to changes in guard cell zeaxanthin
1998
Zhu, J. | Talbott, L.D. | Jin, X. | Zeiger, E.
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 micromole m(-2) s(-1)) and temperature, guard cell zeaxanthin content tracked ambient [CO2] and stomatal apertures. Increases in (CO2] from 400 to 1200 cm(3) m(-3) decreased zeaxanthin content from 180 to 80 mmol mol(-1) Chl and decreased stomatal apertures by 7(.)0 micrometer. 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.
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