Experiments and observations on the aftereffect of wilting on stomata of Rumex sanguineus

Abstract

Stomata of Rumex sanguineus showed an aftereffect of wilting, those of previously wilted plants failing to open as widely as usual. The water content of previously wilted leaves recovered rapidly after watering. The wilting treatment killed about 2% of the guard cells, and was followed by a persistent 5.5 to 7% increase in the carbon dioxide compensation point of leaves. Replacing the air in the intercellular spaces with carbon-dioxide-free air did not remove the aftereffect of wilting on the stomata. Detached leaves also showed the aftereffect, although it was apparently smaller than in leaves attached to the plant. Neither persistent water deficits, nor killing of guard cells, nor increased intercellular space carbon dioxide concentration could explain the aftereffect of wilting on stomata. The results are, however, consistent with the view that an inhibitor of stomatal opening accumulates in leaves after a period of water stress or, alternatively, that there is a deficiency of a substance which promotes opening.