Role of aquaporins in maintenance of xylem hydraulic capacity

Terrestrial plants’ wellbeing depends upon an uninterrupted supply of water from roots to leaves. Water stress or high transpirational demand results in an increase of water tension in the xylem, followed by an increased likelihood of embolism formation and reduction of xylem capacity to conduct water. The prolonged presence of xylem hydraulic dysfunction caused by embolism can have dramatic short- and long-term effects on plant function including the decrease of photosynthetic capacity, reduced vitality, or plant death. As presence of embolisms is a negative trait, plants have evolved several strategies to prevent and/or mitigate the effects of hydraulic failure and restore xylem transport capacity. Recovery process requires a set of physiological activities that promote water flow into embolized conduits to restore its transport function. As hydraulic repair necessitates movement of water across xylem parenchyma cell membranes, an understanding of xylem specific aquaporin expression patterns, their localization and activity is essential for development of biological models describing embolism recovery process in woody plants. In this chapter, we provide an overview of aquaporin distributions and activity during development of drought stress, formation of embolism and subsequent recovery from stress that result in restoration of xylem hydraulic capacity.