The Interaction Between ABA and Sugar Signalling Regulates Stomatal Production in Systemic Leaves by Controlling Sucrose Transport

ABSTRACT A key feature of stress responses [closely relative to the phytohormone abscisic acid (ABA)] and associated acclimation in plants is the dynamic adjustments and related optimisation of carbohydrate content between sink and source organs. The production of stomata, which consist of a pore between two adjacent guard cells, are central to plant adaptation to changing environment conditions. In this context, ABA is a core modulator of environmentally determined stomatal development. It is well established that ABA reduces stomatal aperture but in addition, this hormone also enhances stomatal production. For example, when grown at very high CO 2 levels, Arabidopsis lines with defects in ABA biosynthesis have reduced stomatal production. By contrast, under standard conditions, these ABA biosynthetic mutants show increased stomatal production. However, the molecular mechanism(s) underpinning this regulation remain largely unknown. In this review, we summarise the current knowledge concerning sucrose transport and ABA signalling relating to stomatal production. Further, we provide fresh insights into the possible function of photosynthetic product induced‐ABA as a balancer of carbohydrate accumulation between sink and source organs, to control stomatal production and thereby to adjust stress responses and acclimation in plants, by controlling sucrose transport systems.