Changes in leaf hydraulics and stomatal conductance following drought stress and irrigation in Ceratonia siliqua (Carob tree)

Changes in leaf hydraulic conductance (K) were measured using the vacuum chamber technique during dehydration and rehydration of potted plants of Ceratonia siliqua . K of whole, compound leaves as well as that of rachides and leaflets decreased by 20-30% at leaf water potentials (Psi(L)) of -1.5 and -2.0 MPa, i.e. at Psi(L) values commonly recorded in field-growing plants of the species. Higher K losses (up to 50%) were measured for leaves at Psi(L) of -2.5 and -3.0 MPa, i.e. near or beyond the leaf turgor loss point. Leaves of plants rehydrated while in the dark for 30 min, 90 min and 12 h recovered from K loss with characteristic times and to extents inversely proportional to the initial water stress applied. Leaf conductance to water vapour of plants dehydrated to decreasing Psi(L) and rehydrated at low transpiration was inversely related to loss of K, thus suggesting that leaf vein embolism and refilling (and related changes in leaf hydraulics) may play a significant role in the stomatal response.