Evaluation of the response of maximum daily shrinkage in young cherry trees submitted to water stress cycles in a greenhouse

In the semiarid zones of the Mediterranean area, such as the eastern coast of the Iberian Peninsula, as in many others in the world, water scarcity and the increase of water use in many socio-economical sectors, suppose an urgent need to improve irrigation management. To assess the feasibility of using maximum daily shrinkage (MDS) of the tree trunk as a plant water stress indicator for irrigation scheduling in cherry trees (Prunus avium), an experiment was carried out in 2009 under greenhouse conditions where the relationship of MDS with several environmental and physiological variables was studied. Two years-old cherry trees planted in plastic pots were submitted to several irrigation withholding cycles. Fully irrigated and stressed trees presented differences in all measured physiological variables: leaf stomatal conductance (gs), midday leaf water potential (Ψmd), and daily sap flow (Qd), as expected; and also in MDS which, among the variables measured in the plant, correlated best with Ψmd (r2 = 0.49***). Also a strong (r2 = 0.65***), two phase relationship was found between MDS and substrate matric potential (Ψs) with a linear response of MDS with some scattering till Ψs reached about −33 kPa, followed by a stationary phase with a MDS value about 0.30 mm, a potential threshold for irrigation scheduling of young cherry trees. This value corresponded to Ψmd of −2.3 MPa and gs of 50 mmol m−2 s−1, indicative of water stress. Finally, MDS (which can be considered an adequate indicator of cherry tree water status given its strong relation with other indicators of plant water status) was the most sensitive and early indicator of water stress (highest signal to noise ratio) of the measured physiological variables. This high sensitivity makes it a potential candidate indicator for irrigation scheduling in young cherry trees, if the threshold obtained in this work can be validated or any other can be established.