The influence of drought on stomatal conductance and water potential of peach trees growing in the field

Abstract

Stomatal conductance and leaf and stem water potentials were measured on peach trees irrigated at 50 and 100% of calculated maximum evapotranspiration (MET) in order to determine the influence of soil drying on these indicators of plant water stress. In addition, the relationship between stomatal conductance and air vapor pressure deficit was examined. Stomatal conductance and daily leaf and stem water potentials have been shown to decrease linearly with decreasing soil water content averaged over the upper 60 cm of soil. Pre-dawn water potential was insensitive to the drying of the soil over a wide range of soil water contents, and decreased sharply after a threshold value was reached. A multiple regression analysis showed that the leaf water potential and the air vapor pressure deficit explained 49% of the stomatal conductance variance. However, our data did not allow us to show whether the influence of soil drying on stomatal conductance was direct or mediated by the leaf water potential.