The stomatal response to CO2 is linked to changes in guard cell zeaxanthin* |
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Authors: | J Zhu L D Talbott X Jin & E Zeiger |
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Institution: | Department of Biology, University of California, Los Angeles, CA 90095–1606, USA |
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Abstract: | 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 μ mol 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 μ m. 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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Keywords: | Vicia faba stomatal response to CO2 xanthophyll cycle zeaxanthin |
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