When plants are exposed to unfavorable environmental conditions, stomatal movement is one of the immediate plant responses. To facilitate stomatal movement, a pairs of guard cells that comprise the stomata have evolved robust mechanisms to sense and respond to various endogenous and environmental stimuli. The “Ca2+-sensitivity priming” model has been recently appreciated as an important mechanism for driving stomatal movements under multiple stimuli (Hubbard et al., 2012 and Laanemets et al., 2013).