Xylem and stomata, coordinated through time and space

Land plants exhibit a degree of homeostasis in leaf water content to protect against damage to photosynthetic and xylem tissues, and to maintain an efficient allocation of resources. This is achieved by a strong coordination between the systems regulating water delivery (xylem) and water loss (stomata). This review discusses evolution in xylem and stomatal function, specifically focussing on the interactions between them. Vascular plants incur penalties for allowing leaf hydration to range outside strict limits of hydration. Xylem and stomatal tissues regulate the acquisition and loss of water in leaves, and they must work together to maintain a safe level of leaf hydration. This review examines how xylem and stomatal tissues are coordinated to achieve this important role.