Repeated measurements of aperture for individual stomates.

Measurements of stomatal aperture in epidermal peels are used in a variety of physiological studies, but variability between stomates often hinders experimentation. We mount epidermal peels of Vicia faba over a microscopic grid that enables us to map the positions of individual stomates and thus measure the same individual stomates repeatedly, using a simple digitizing system. Repeated measurements of the same population of 15 stomates show much lower variability than measurements of different populations either on the same peel or on different peels.