Some Problems of the Determination of Stomatal Aperture by the Microrelief Method

The applicability of the microrelief (or reprint) method for stomatal aperture determinations was studied in middle-aged sugar beet leaves. It was found that the picture of the central aperture (CA) of stomata on the reprints could be observed only if their eisoiial aperture (EA) was sufficiently wide. If the width of EA was small (about 1–3 μ), it was impossible to determine the width of CA by means of the reprint method, in view of the proportional dimensions of the upper closing flaps. A lower concentration of the chlorophorm solution of methylmethacrylate used for taking reprints had a favourable influence on the amount of stomata whose width of central aperture was reproduced on the reprints. Simultaneous measurements of the EA-width and of the diffusibility of leaves (determined porometrically) in the course of a day showed, on the whole, fairly corresponding changes. During the wilting of detached leaves their diffusibility fell to zero, where it remained. The width of EA also decreased at first, but at higher water deficits it partly again increased.