Light Saturation of Stomatal Opening on the Adaxial and Abaxial Epidermis ofCommelina communis

The responses of adaxial and abaxial stomata to light were examined on detached epidermis of Commelina communis. Stomata on the abaxial epidermis were considerably more sensitive to light than those on the adaxial epidermis, supporting the view that the differences in photosensitivity are inherent rather than the result of differences in the microenvironment within the leaf. The sensitivity of adaxial and abaxial stomata to blue light was also examined. The quantum flux received by a pair of guard cells appears to be sufficient to support a direct effect of blue light on ion transport into the guard cells, but there is no evidence to suggest that blue light is essential for stomatal opening.