Grapevine canopy response to a high-temperature event during deficit irrigation

Background and Aims: Despite much anecdotal evidence, there has been little scientific investigation of the potential effects of a high-temperature event on grapevines during deficit irrigation. This study examined the interaction between temperature and water status on leaf physiology. Methods and Results: Two experiments used Cabernet Sauvignon cuttings grown in a glasshouse at approximately 27-30 degrees C before deficit irrigation treatments were imposed. When water stress was apparent, a 2-day high-temperature event with maximum daytime temperatures of approximately 40-45 degrees C was generated. Leaf damage, stomatal conductance and water potential of deficit-irrigated vines were all affected to a greater extent than in the well-watered vines. Conclusions: The negative effects of a high-temperature event on vine physiology were more severe in vines experiencing water stress than in well-watered vines, but recovery was rapid even without re-watering. Significance of the Study: An increase in the use of deficit irrigation will lead to a greater likelihood of vines being water stressed on hot days, and the observed responses indicate that this will result in greater damage to the vine.