Plant and leaf responses to cycles of water stress and re-watering of 'Sangiovese' grapevine

The complex relationship between water and grapevine has been examined in several studies. The aim of this study was to understand the impact of water stress on photosynthesis, carbon-13 discrimination in leaves in different positions on the shoot, and the capacity of vines to recover from different levels of water stress intensity. The vine physiological responses to a water stress regimen followed by re-watering for two consecutive cycles was evaluated using potted 'Sangiovese' grapevines. The intensity and the duration of the water limitation affected the emergence and development of new leaves, but did not significantly affect leaf water potential. Leaf stomatal conductance and carbon assimilation during the first water-stress phase were reduced respectively by about 61% and 20%, while after the second water stress cycle both were lower than the initial values by 77% and 21%, respectively. After 1 day of re-watering, only the leaves located in the medial positions on the shoot showed a partial recovery of photosynthesis. After at least 2 days post-re-watering, the leaves located in the distal portion of the shoot showed a recovery of photosynthetic capacity. The results indicated that leaf position along the shoot, i.e., an indicator of leaf age, is an important variable in developing grapevine strategies in response to conditions of limited water availability.