Plant and Leaf Physiological Responses to Water Stress in Potted ‘Vignoles’ Grapevine

Several studies have investigated water relationships in grapevines, but the responses to water limitation on individual leaves developed in different shoot positions are scarce in the literature. To begin to fill-in this gap, we examined the adaptive responses of vines at the leaf level to varying amounts of water stress using young hybrid ‘Vignoles’ in a controlled growth chamber. We found that the reduction in water availability to 40% of daily evapotranspiration limited shoot and leaf growth, affecting leaf number, shoot elongation, and leaf area. After 2 days of water stress we observed young developing leaves (nodes six to eight from the shoot apex) to have drastically reduced stomatal conductance ( g S , about 20 mmol H 2 O/m 2 /s) and net photosynthesis (P n , 2 μmol CO 2 /m 2 /s). On the 4th day P n in mature leaves (nodes 9 to 12 from the shoot apex) fell to values below 2 μmol CO 2 /m 2 /s. After 6 days, both P n and g S stabilized at lower values with fluctuations related only to leaf position along the shoot axis. Young leaves revealed substantial enrichment of carbon-13 ( 13 C) and high water-use efficiency suggesting a higher and faster adaptive capacity to water shortage conditions as compared with mature leaves.