Response of leaf water potential to estimated transpiration in almond trees

Abstract

SummaryAlmond plants (Amygdalus communis L. cv. Garrigues) were grown in the field under drip irrigated and rainfed conditions. Leaf water potential of sunlit leaves (ψ1) and of non-transpiring leaves close to the sunlit ones (ψs) were measured at three different times in the growing season (spring, summer and autumn). Daily courses of ψ1 and ψs showed a dependence on the absolute humidity difference from leaf to air (ΔH). The calculated difference between ψs and ψ1 (ψs–ψ1 = Δψ), which gives a measure of leaf transpiration, was higher in wet than dry treatments, decreasing in the last case by the effect of accumulated water stress on stornata. The relationships between api and Aap pointed to a progressive decrease in leaf water potential as leaf transpiration increased, suggesting the presence of a substantial internal plant resistance to water flow.Abbreviations: ψ1, leaf water potential; ψs, stem water potential, Δψ = ψs–ψ1; ΔH, absolute humidity difference from leaf to air.