Calcium Signals in the Control of Stomatal Movements

The stomatal guard cell regulates gas exchange between the plant and the environment. The movements of the stomata are regulated by a myriad of signals. The signalling pathways regulating stomatal movements have been intensely investigated due to their importance in plant responses to environmental stresses and because transpiration from the stomatal pore is the major route for water flux from the soil to the atmosphere, having consequence for climate models. The ubiquitous second messenger, calcium, is an important regulator of stomatal movements. The role of calcium as a second messenger in abscisic acid-induced stomatal closure is described. The importance of repetitive oscillations in the concentration of cytosolic free Ca2+ is discussed. The use of network reconstruction tools and systems approaches to understanding the relationship between calcium signalling and the recently discovered kinase/phosphatase-based ABA signalling cascade is considered.