SUMMARYAdult early maturing peach trees (Prunus persica(L.) Batsch cvar Flordastar) grafted ontoP. persica×Prunus amygdalusGF-677 peach rootstock, were subjected to low water availability (water stress) and recovery periods for 28 and 7 days, respectively, during summer 2009. Control plants were irrigated daily at 1·3 estimated crop reference evapotranspiration (ETC) in order to obtain non-limiting soil water conditions. Active osmotic adjustment was observed at the end of the stress period. However, the magnitude of this osmotic adjustment (0·18 MPa) was not sufficient to modify the leaf water potential at turgor loss point. The observed active osmotic adjustment that maintained turgor was in contrast to other results in potted peach trees, where no osmotic adjustment was observed, and highlights the importance of field studies in which water stress is developed gradually over a prolonged period. Relative apoplastic water content (RWCa) values were high and decreased as a result of water stress. The rapid decrease in leaf conductance from the beginning of the stress period, together with the delay in stomatal reopening after rewatering, indicated that stomatal behaviour was not a simple passive response to water deficit. The results indicate that drought resistance in early maturing peach trees is based both on avoidance mechanisms, such as stomatal control and tolerance mechanisms, including active osmotic adjustment and high RWCa.
Daily sap flow and maximum daily trunk shrinkage measurements for diagnosing water stress in early maturing peach trees during the post-harvest period
