Engineering stomata for enhanced carbon capture and water-use efficiency

Stomatal pores facilitate gaseous exchange between the inner air spaces of the leaf and the atmosphere. As gatekeepers that balance CO2 entry for photosyn-thesis against transpirational water loss, they are a focal point for efforts to im-prove crop performance, especially in the efficiency of water use, within the changing global environment. Until recently, engineering strategies had fo-cused on stomatal conductance in the steady state. These strategies are lim-ited by the physical constraints of CO2 and water exchange such that gains in water-use efficiency (WUE) commonly come at a cost in carbon assimilation. Attention to stomatal speed and responsiveness circumvents these constraints and offers alternatives to enhancing WUE that also promise increases in carbon assimilation in the field.