Leaf hydraulic capacitance is key determinant of grapevine drought control.

The grapevine is used as model plant to understand plant strategies to avoid/tolerate water stress. Two Vitis vinifera L. varieties have been described to represent them. ‘Grenache’ points to stress avoidance, acting abscisic acid (ABA)-driven stomatal closure and maintaining high levels of leaf water potential during water stress (isohydric response). On the contrary, ‘Syrah’ does not strictly control stomatal closure upon drought and tolerates a water potential decrease through osmoregulation (anisohydric behavior). By following stress/recovery routines we found a strategic contribution of leaf hydraulic capacitance in isohydric leaves, that allows water retaining in leaves during drought. In isohydric plants, a rehydration after a water shortage period causes a transient decrease in leaf turgor, by restoring stomatal opening and following transpiration. On the contrary, rehydrated water droughted anisohydric plants recover leaf turgor and water potential through a hydraulic, non-hormonal control of stomatal behaviour.