Interactive effects of high temperature and water deficit on Malbec grapevines

Abstract

Background and Aims: Studies of the interactive effects of drought and high temperature on the physiological responses of grapevines (Vitis spp.) are scarce. We tested whether well‐watered, potted vines were able to avoid heat waves through evaporative cooling in comparison to those suffering from water deficit. Methods and Results: A greenhouse experiment was conducted with own‐rooted Malbec grapevines under two water regimes, well‐watered (100% of pot capacity) and water deficit (50% of pot capacity), and two air temperature regimes, high (45/22°C) and Control temperature (35/20°C). Short‐term stomatal and non‐stomatal regulation of photosynthesis was assessed by measuring leaf gas exchange, stomatal conductance (g s) and chlorophyll fluorescence. Whole‐plant transpiration and vegetative growth were also measured. In well‐watered vines, high air temperature increased g s and leaf transpiration (E leaf), which decreased leaf temperature and increased vegetative growth, whole‐vine transpiration and leaf net photosynthesis (P n). Water deficit strongly reduced growth, P n, g s and E leaf. For vines under high temperature, however, reduction in P n, g s and E leaf was smaller than for that under the Control temperature. Conclusions: Evaporative cooling may help well‐watered grapevines withstand heat waves and avoid irreversible reduction in gas exchange and chlorophyll fluorescence.