TY - JOUR T1 - Aspects of Water Relations of the Grapevine (Vitis Vinifera) JF - American Journal of Enology and Viticulture JO - Am J Enol Vitic. SP - 84 LP - 91 DO - 10.5344/ajev.1974.25.2.84 VL - 25 IS - 2 AU - R. E. Smart Y1 - 1974/01/01 UR - http://www.ajevonline.org/content/25/2/84.abstract N2 - Diurnal patterns of leaf water potential (ψ) and stomatal resistance (rs) were investigated under different irrigation treatments and evaporative conditions. The ambient environment, especially solar radiation, had a dominating effect on leaf ψ. Water-stress-induced stomatal closure was observed at ψ of —13 bars, though shoot growth rate was inhibited before negative tensions became that large. Trunk diameter was very sensitive to water stress, even to hourly changes. Demonstrated as a simple yet effective indicator of water stress was the angle between the petiole and the lamina midrib. ER -