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

• Published in: BMC plant biology Vol. 23; no. 1; p. 369
• Main Authors: Groenveld, Thomas, Obiero, Charles, Yu, Yingxue, Flury, Markus, Keller, Markus
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 25.07.2023; BioMed Central; BMC
• Subjects: Analysis; Cultivars; Diseases and pests; Disequilibrium; Droughts; Environmental aspects; Equilibrium; field experimentation; Flowers & plants; Genetic aspects; Grapes; Grapevines; Growth; Hydraulics; Hydrostatics; leaf water potential; Leaves; Moisture content; Moisture effects; Nighttime transpiration; Regression analysis; Retention; Soil conditions; Soil moisture; Soil water; Soil water potential; Transpiration; United States; vineyards; Vitis; volumetric water content; Water content; Water potential; Water relations; Wineries & vineyards; Wines; United States; Model; Disequilibrium; Vitis; Soil water potential; Nighttime transpiration
• ISSN: 1471-2229; 1471-2229
• DOI: 10.1186/s12870-023-04378-6

In plant water relations research, predawn leaf water potential (Ψ ) is often used as a proxy for soil water potential (Ψ ), 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 Ψ  = Ψ for field-grown grapevines. 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 Ψ and the volumetric soil water content (θ ) under each sampled plant were measured multiple times during several dry-down cycles. The results show that in wet soil (Ψ  >  - 0.14 MPa or relative extractable water content, θ  > 0.36), Ψ was significantly lower than Ψ for all 30 cultivars. Under dry soil conditions (Ψ  <  - 0.14 MPa or θ  < 0.36) Ψ lined up better with Ψ . There were differences between cultivars, but these were not consistent over the years. These results suggest that for wet soils Ψ of grapevines cannot be used as a proxy for Ψ , while the Ψ  = Ψ assumption may hold for dry soils.