Effect of previous water conditions on vine response to rewatering

A comparative study of stomatal responses to rewatering was conducted on grapevines previously subjected to conditions of water stress and no water stress. Two cultivars were grown in 35 L lysimeters: 'Airén', from the dry zone of La Mancha, and 'Chardonnay', from the humid zone of Burgundy. The day after rewatering no significant differences in soil water content were found between water treatments or cultivars. However, predawn leaf water potential was significantly higher under non-stress than under stressed conditions, differences between cultivars were also found. Water consumption during the 5 d after rewatering was directly related to vine leaf area development. Vines grown under water stress conditions showed more uniform stomatal behaviour after rewatering. One day after rewatering rates of leaf conductance, transpiration and net photosynthesis were significantly higher in non-stressed vines, while 3 d after rewatering leaf conductance and transpiration were significantly higher in vines previously subjected to water stress. Net photosynthesis was significantly higher in water-stressed vines 5 d after rewatering. No differences were found between cultivars with regard to leaf conductance. The differences in the relationship between net photosynthesis and leaf conductance between stressed and non-stressed vines before rewatering were not found after rewatering. The only permanent adaptation mechanism to water stress was a lowering of leaf area development, which allowed water-stressed vines to consume less water to maintain a higher water availability and high or constant stomatal conductance.