Abstract
The stimulation by KCl of stomatal opening in isolated epidermal strips of Vicia faba was examined. In dark + normal air the opening response was maximal at 100 mm KCl while in light + CO2-free air it was maximal at about 10 mm KCl. CO2-free air was more influential than light in reducing the KCl concentration required for maximal opening. K+ was essential while Cl− seemed to be of secondary importance in these processes.
The use of 86Rb+ as a tracer for K+ showed that the increase in stomatal aperture under various conditions was well correlated with K+ uptake. The estimated amount of K+ taken up by guard cells, along with a counter ion, was sufficient to account for the changes in solute potential associated with opening. It is suggested that the absorption of extracellular solutes, such as K+, may be the primary mechanism of stomatal opening. Both opening and K+ absorption are stimulated by light + CO2-free air.
The increase in stomatal aperture was also well correlated with the decrease in stainable starch in guard cells under all conditions. It is suggested that this is a secondary change, although perhaps closely linked to K+ absorption.
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Selected References
These references are in PubMed. This may not be the complete list of references from this article.
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