Effects of silicon on tolerance to water deficit in peach trees

Young fruit trees are not irrigated during tree establishment (first two years after planting) in subtropical humid regions such as the southeastern US. However, drought periods often cause tree water deficits that may lead to reductions in tree growth and affect the long-term productivity of orchards. The objective of this study was to evaluate the effect of foliar applications of silicon (Si) on water status and gas exchange of young peach trees. Sixty two-year-old peach trees grown in pots were either well-irrigated (100% evapotranspirative needs; ETc) or water-stressed (50% ETc). One week after tree water status of these irrigation treatments were clearly differentiated, three concentrations of Si were applied to ten trees per treatment: Control (no Si), 10 mg L^‑1 Si, and 20 mg L^‑1 Si. Foliar applications (0.42 L tree^‑1) were performed weekly over a period of six weeks, and leaf Si concentration, tree water status (midday stem water potential), and gas exchange parameters (stomatal conductance, leaf transpiration) were measured weekly. Foliar applications of Si significantly increased the leaf Si concentration compared to control trees. Results showed that Si applications at both rates significantly improved water status of drought-stressed trees and helped trees recover faster from the stress upon rewatering.