Abstract
Flooding the intercellular air spaces of leaves with water was shown to cause rapid closure of stomata in Tradescantia pallida, Lactuca serriola, Helianthus annuus, and Oenothera caespitosa. The response occurred when water was injected into the intercellular spaces, vacuum infiltrated into the intercellular spaces, or forced into the intercellular spaces by pressurizing the xylem. Injecting 50 mm KCl or silicone oil into the intercellular spaces also caused stomata to close, but the response was slower than with distilled water. Epidermis-mesophyll grafts for T. pallida were created by placing the epidermis of one leaf onto the exposed mesophyll of another leaf. Stomata in these grafts opened under light but closed rapidly when water was allowed to wick between epidermis and the mesophyll. When epidermis-mesophyll grafts were constructed with a thin hydrophobic filter between the mesophyll and epidermis stomata responded normally to light and CO(2). These data, when taken together, suggest that the effect of water on stomata is caused partly by dilution of K(+) in the guard cell and partly by the existence of a vapor-phase signal that originates in the mesophyll and causes stomata to open in the light.
Highlights
IntroductionHelianthus annuus, and Oenothera caespitosa. The response occurred when water was injected into the intercellular spaces, vacuum infiltrated into the intercellular spaces, or forced into the intercellular spaces by pressurizing the xylem
Lactuca serriola, Helianthus annuus, and Oenothera caespitosa
To verify the original observation that stomata do not open in the presence of free water in epidermismesophyll grafts from Tradescantia pallida, we constructed grafts and allowed stomata to open until apertures were stable
Summary
Helianthus annuus, and Oenothera caespitosa. The response occurred when water was injected into the intercellular spaces, vacuum infiltrated into the intercellular spaces, or forced into the intercellular spaces by pressurizing the xylem. There are two assumptions about stomata that are implicit in much of the recent literature: (1) that stomatal responses result from sensory mechanisms that reside within the guard cells, and (2) that stomata in isolated epidermes respond to those in a leaf. A third study has shown that isolated epidermes are much more sensitive to light and CO2 when placed in close contact with an exposed mesophyll from a leaf from the same or a different species (Mott et al, 2008) These epidermis-mesophyll grafts showed stomatal responses to light and CO2 that were indistinguishable from those in an intact leaf—a sharp contrast to the behavior of stomata in isolated epidermes that are. This study was initiated to test these three hypotheses by examining the effect of free water and other liquids on stomatal functioning
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