Midday measurements of leaf water potential and stomatal conductance are highly correlated with daily water use of Thompson Seedless grapevines |
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Authors: | Email author" target="_blank">L?E?WilliamsEmail author P?Baeza P?Vaughn |
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Institution: | 1.Department of Viticulture and Enology,University of California,Davis,USA;2.Kearney Agricultural Center,Parlier,USA;3.Departamento de Producción Vegetal: Fitotecnia,Universidad Politécnica de Madrid,Madrid,Spain;4.Water Management Research Laboratory,USDA-ARS,Parlier,USA |
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Abstract: | A study was conducted to determine the relationship between midday measurements of vine water status and daily water use of
grapevines measured with a weighing lysimeter. Water applications to the vines were terminated on August 24th for 9 days and
again on September 14th for 22 days. Daily water use of the vines in the lysimeter (ETLYS) was approximately 40 L vine−1 (5.3 mm) prior to turning the pump off, and it decreased to 22.3 L vine−1 by September 2nd. Pre-dawn leaf water potential (ΨPD) and midday Ψl on August 24th were −0.075 and −0.76 MPa, respectively, with midday Ψl decreasing to −1.28 MPa on September 2nd. Leaf g
s decreased from ~500 to ~200 mmol m−2 s−1 during the two dry-down periods. Midday measurements of g
s and Ψl were significantly correlated with one another (r = 0.96) and both with ETLYS/ETo (r = ~0.9). The decreases in Ψl, g
s, and ETLYS/ETo in this study were also a linear function of the decrease in volumetric soil water content. The results indicate that even
modest water stress can greatly reduce grapevine water use and that short-term measures of vine water status taken at midday
are a reflection of daily grapevine water use. |
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