Cyclic variations of stomatal aperture observed under the scanning electron microscope

Abstract

Scanning electron micrographs taken from a vertical position revealed the stomatal aperture at the central pore and at the outer ledge. Cyclic variations in leaf temperature of tobacco (Nicotiana tabacum cv. MC) and sunflower (Helianthus annuus cv. Large Russian) after illumination coincided with the aperture at the central pore, but did not always at the outer ledge. The relative turgidity of leaf was inversely proportional to the aperture at the outer ledge. Moreover, the opening at the central pore was an “8”-shaped aperture provided the opening was small. Thus, the present experiments indicated the importance in measurement of the stomatal aperture at the central pore for quantitative and qualitative determination of cyclic variations in the stomatal aperture.