Predawn leaf water potential of grapevines is not necessarily a good proxy for soil moisture

Abstract

Background In plant water relations research, predawn leaf water potential (Ψpd) is often used as a proxy for soil water potential (Ψsoil), without testing the underlying assumptions that nighttime transpiration is negligible and that enough time has passed for a hydrostatic equilibrium to be established. The goal of this research was to test the assumption Ψpd = Ψsoil for field-grown grapevines. Results A field trial was conducted with 30 different cultivars of wine grapes grown in a single vineyard in arid southeastern Washington, USA, for two years. The Ψpd and the volumetric soil water content (θv) under each sampled plant were measured multiple times during several dry-down cycles. The results show that in wet soil (Ψsoil > − 0.14 MPa or relative extractable water content, θe > 0.36), Ψpd was significantly lower than Ψsoil for all 30 cultivars. Under dry soil conditions (Ψsoil < − 0.14 MPa or θe < 0.36) Ψpd lined up better with Ψsoil. There were differences between cultivars, but these were not consistent over the years. Conclusion These results suggest that for wet soils Ψpd of grapevines cannot be used as a proxy for Ψsoil, while the Ψpd = Ψsoil assumption may hold for dry soils.

Predicting the canopy conductance to water vapor of grapevines using a biophysical model in a hot and arid climate

“…Several authors have documented a strong correlation between leaf stomatal conductance and soil water content (Dry and Loveys, 1999;Tuzet et al, 2003;Prieto et al, 2010;Costa et al, 2012;Lavoie-Lamoureux et al, 2017), and between soil water content and predawn leaf water potential (Williams and Araujo, 2002;Groenveld et al, 2023). This article emphasizes the role of grapevine water status, in controlling leaf stomatal conductance, and demonstrates a strong correlation between canopy conductance and vine transpiration.…”

Nitric Oxide Mitigates the Deleterious Effects Caused by Infection of Pseudomonas syringae pv. syringae and Modulates the Carbon Assimilation Process in Sweet Cherry under Water Stress

“…In the 2022 season, the assay was maintained for 36 days and pots were covered with a plastic cover to favor a slow substrate desiccation. In this season, instead of the pot weighing, which is highly time consuming, the pre-dawn water potential (Ψ pd ) was used as a proxy for the soil water content [93]. Each treatment was composed of three experimental units, with three plants per unit, giving 9 plants per treatment, i.e., 36 plants in total (Supplementary Figure S2a).…”