Stomata as an important hub for the ecophysiology of leaves and nonfoliar tissues

The epidermis of leaves and nonfoliar tissues (eg, stems, flowers, and fruits) can contain microscopic structures named stomata, formed by 2 guard cells surrounding a pore. Stomatal opening allows the exchange of CO2 and H2O between the organ and the atmosphere. Stomatal development and movement are regulated by the integration of endogenous and environmental signals and are tightly connected to plant hydraulics, photosynthesis (A), and transpiration (E). Stomata are therefore at the intersection of the perception of environmental cues and the regulation of water use efficiency (WUE-A/E). Here, we review how environmental and endogenous signals influence stomatal density and conductance (gs) and how this is connected to A, WUE, and plant hydraulic safety. We also provide an update on the importance of stomata for foliar water uptake and how sucrose integrates A and gs thereby WUE by regulating both stomatal opening and closure. We highlight the need to consider stomatal responses in a wider spatiotemporal context and to increase the interdisciplinarity among stomatal physiologists to establish studies and models better representing the modularity and the nonlinearity of gs in leaves and non-leaf tissues.