Water stress in young fruit trees can reduce tree growth and impair future crop productivity. Silicon (Si) has shown a positive effect in mechanisms related to water relations, specifically water uptake and transport, as well as physiological and anatomical changes in leaves of annual plants. These findings suggest that Si could induce adaptive changes that could help trees cope with water deficit. The objective of this experiment was to evaluate the role of Si on water status, sap flow, and gas exchange of young peach trees under water deficit. Two-year-old ‘Julyprince’ peach trees grown under controlled conditions received either 100% (well-watered trees) or 50% (stressed trees) of their crop evapotranspiration needs three times a week. Once trees in the two treatments displayed a difference in water status, Si was applied weekly by foliar spray (0 or 20 mg L-1). The combination of these two factors resulted into a completely randomized factorial design with four treatments. Results showed an interaction between irrigation regime and Si application. Si increased sap flow in well-watered trees and reduced that of stressed trees, although this effect was more significant the day after irrigation. Furthermore, Si significantly improved the water status of trees under water deficit but did not influence that of well-watered trees. These results seem to indicate that the role of Si in improving tolerance to water deficit is temporary and dependent on the tree water status.
