Update: Ion transport at the vacuole during stomatal movement

Gas exchange and transpiration are regulated by the stomatal aperture, which is itself regulated by the changes in volume of the guard cells that overlay the stomatal pore. When triggered to open, solutes such as K⁺ and Cl^– enter the guard cell through ion transporters, followed osmotically by water; as the cells enlarge, the gap between them widens permitting gas and water vapour transit. Ion transporters at the guard cell plasma membrane are more accessible for patch clamping, and in recent years our knowledge of these essential transporters has increased dramatically. However, ultimately it is the movement of ions and water into the vacuole that controls stomatal aperture, and our understanding of the tonoplast (vacuolar membrane) transporters lags behind those of the plasma membrane. Eisenach and De Angeli review ion transport at the guard cell vacuole, drawing on electrophysiological studies and results from Arabidopsis genetics, and discussing the contributions of vacuolar pH and membrane potential to stomatal movement. Plant Physiol. 10.1104/pp.17.00130