Background

The epidermis of all leaves has specialized cells, the guard cells, surrounding microscopic pores. The guard cells and pores are called stomata, and they permit gas exchange and diffusion of water vapor between the atmosphere and the interior of the leaf. Stomata are products of an intracellular program, which generates the specific stomatal patterns during their development (Kagan et al., 1992). Stomata are found both in the abaxial and adaxial sides of the leaf, although the stomatal density (and starch accumulation) is higher on the abaxial side of the leaf sheath in Arabidopsis thaliana (Schlüler et al., 2003; Tsai et al., 2009). The stomatal density is controlled by endogenous and exogenous factors in Arabidopsis thaliana (Berger and Altmann, 2000; von Groll et al., 2002). Stomatal aperture actively responds to changes in the environment and regulates leaf transpiration rates (Santelia and Lawson, 2016). An accurate estimation of the stomatal aperture provides insight into the impact of environmental stress on plants.