Stem water potential is a sensitive indicator of grapevine water status

Dawn leaf water potential (dawn Psi), leaf water potential (leaf Psi) and stem water potential (stem Psi) were measured on mature leaves to determine non-irrigated vine water status in vineyards during the growing season. Stem Psi was the most discriminating indicator for both moderate and severe water deficits. The difference between stem Psi and leaf Psi (Delta Psi) provided an indirect measurement of mean leaf transpiration which varied with soil moisture conditions and vapour pressure deficit in the atmosphere. The use of stem Psi as an indicator for grapevine management in both nonirrigated and irrigated vineyards is discussed. (C) 2001 Annals of Botany Company.