Aspects of Water Relations of the Grapevine (Vitis Vinifera)

Abstract

Diurnal patterns of leaf water potential (ψ) and stomatal resistance (r_s) 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.