How water capacitance works in trees

Forests in western Europe are particularly vulnerable to drought events and heat waves, which are becoming more frequent and severe. Trees can, however, defend against extreme water scarcities using hydraulic capacitance within xylem (vessels that transport water from the roots through the rest of the plant).

The precise physical and genetic mechanisms of this hydraulic capacitance process have remained unclear, but the EU-funded TREE CAPACITANCE project gained new insights. Using several hybrid and control poplars, researchers were able to unravel the physical mechanisms of capacitance during water deprivation and normal conditions.

They also determined that two genes, aquaporins (AQPs) and wall-associated kinases (WAKs), are differentially regulated under changing plant water status. AQPs code for water channel proteins, while WAKs code for proteins that are bound to the cell wall and to the plasma membrane.

These findings support the hypothesis that WAKs can sense dehydration and then regulate the activity of aquaporins accordingly.

TREE CAPACITANCE researchers thus shed new light on how the hydraulic capacity of xylem water reservoirs buffers the effects of drought stress in trees. This research will support European forest production and environmental protection efforts in the face of climate change.