Response of Physiological Activities and Vine Performance of Field Grown ‘Sultan 7’ (Vitis Vinifera L.) Variety to Different Water Status in Mediterranean Conditions

This study was carried out to investigate the effects of different irrigation treatments (Ir100, Ir66, Ir33) on physiological activities and vine performance of the field-grown ‘Sultan 7’ variety. Overall, stomatal conductance (gsw) and net CO₂ assimilation (A) values were lower in the veraison–harvest than in the fruit set–veraison period regardless of irrigation treatments. In both periods, Ir33 was the most restrictive treatment on gas exchange parameters. However, gsw values under all treatments varied in the range of mild stress thresholds (150.39–381.01 mmol m² s¹). In this regard, vegetative growth parameters, particularly pruning wood weight and Ravaz index, were not influenced significantly by irrigation regimes, suggesting that gsw is a trustworthy parameter to detect the water stress level of vines. Although ‘Sultan 7’ vines reached severe stress levels according to midday leaf water potential (Ψ_md) values (between −1.51 and −1.64 MPa) under deficit irrigations, the vines remained at mild stress levels according to gsw values. This shows that ‘Sultan 7’ vines might be more resistant to stress conditions because they remained at the mild stress level even under deficit irrigation. Consequently, ‘Sultan 7’ dried grape growing can be achieved without reducing vine performance under deficit irrigation strategies in the experiment and water use efficiency can be increased by saving water.