Stomatal opening quantitatively related to potassium transport: evidence from electron probe analysis.
When stomata of Vicia faba opened (from a stomatal aperture of about 2 micrometers to one of 12 micrometers) the solute content of the guard cells increased by 4.8 x 10(-12) osmoles per stoma. During the same time an average of 4.0 x 10(-12) gram equivalents of K(+) were transported into each pair of guard cells. This amount of K(+), if associated with dibasic anions, is sufficient to produce the changes in guard cell volume and osmotic pressure associated with stomatal opening. Analysis of Cl, P, and S showed that these elements were not transported in significant amounts during stomatal opening. This finding suggests that the anions balancing K(+) were predominantly organic. K(+) was specifically required because no other elements, likely to be present as cations, were found to accumulate in appreciable quantities in guard cells of open stomata.
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Michigan State University-Atomic Energy Commission Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48823.
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