Stomatal Response of Three Grapevine Cultivars ( Vitis vinifera L.) to High Temperature

Abstract

Potted Cardinal, Chardonnay, and Chenin blanc vines were subjected to heat stress of 40°C and 20°C (day and night temperatures, respectively) for periods of 0 (control), four, eight, and 12 days before returning the vines to optimal day temperature conditions of 25°C to 29°C in a greenhouse for an eight-day "recovery period". Root temperatures were maintained constant during the heat stress period by holding the pots in a water bath. Stomatal conductance, predawn leaf water potential, air and leaf temperatures, relative humidity, and photosynthetic active radiation were measured throughout the experiment. Heat stress markedly reduced stomatal conductance (Cs) in Chardonnay and Chenin blanc vines. Under optimal temperature conditions (25° to 29°C/15° to 16°C day/night temperatures), Chardonnay vines had the highest Cs, followed by Chenin blanc and Cardinal, whereas under heat stress (40°C), Chenin blanc had the highest Cs, followed by Chardonnay and Cardinal. However, Cardinal was the least affected of the three cultivars. Within one to four days after heat-stressed vines were returned to optimal day temperature conditions, Cs was similar to that of control vines.