ALT Diagram of open (left) and closed (right) stomata complexes, illustrating the mechanism by which overexpression of ACA11 facilitates the accumulation of Ca2+ in the vacuole, influencing Ca2+ storage and leading to an enhanced Ca2+ elevation in response to ABA. A computer screen is shown, indicating the role of the OnGuard quantitative model, which accurately represents the mechanics and coordination of ion transporters in guard cells.