## 3 Results
#### 3.1.1 Vine Water Status and Leaf Gas Exchange  
Clones 4, 94, and 188 maintained a better vine water status (measured by \(\Psi_{\mathrm{s}}\)) and a greater gradient of water potential (\(\Delta\)V) in the leaves (4 and 188) than clones 360, 372, and 276 (Table 3). This was also reflected in significantly greater rates of daily leaf gas exchange (\(A\), \(g_{\mathrm{s}}\), and \(E\)) maintained during the growing season, especially in clone 4, followed by clones 94 and 188, compared to clones 360, 372, or 276. These differences were more accentuated during the post-veraison period. In addition, \(Ci\) was also significantly higher in clones 4 and 94 (pre-veraison, 2020) and clones 4, 94, and 188 (post-veraison, 2020) compared to the rest of the clones (especially clones 372 and 360 with lower \(g_{\mathrm{s}}\) and \(Ci\)) (Table 3). Moreover, high-vigor clones (especially clone 4) were significantly more efficient in the photosynthetic nitrogen use (NUEph) than low-vigor clones, and particularly clone 360, which showed the lowest NUEph (Table 3). Clone 4 was the least efficient in water use at the leaf level (lower \(A\)/\(g_{\mathrm{s}}\), \(A\)/\(E\)), especially during the post-veraison period (2020), compared to 94 and 188 and even to the rest of the clones. In contrast, clone 360, the most water-stressed (followed by 372 and 276), showed the highest \(A\)/\(g_{\mathrm{s}}\) and \(A\)/\(E\) (post-veraison, 2020). In addition, carbon isotopic (\(\delta^{13}\)C) in berries, a surrogate parameter that acts as an indicator of long term WUE, was also significantly lower (more negative) in vines from clone 4 than in vines from other clones (Table 3). Conversely, clones 360, 372, and 276 showed the highest values of \(\delta^{13}\)C in berries (in 2019 and 2020). There were significant negative linear relationships between \(A\)/\(g_{\mathrm{s}}\), WUE\({}_{\mathrm{yield}}\), \(A\)/\(g_{\mathrm{s}}\), and yield (Figure 2A-D), between WUE\({}_{\mathrm{yield}}\) and \(\delta^{13}\)C (Figure 2E,G), and between yield and \(\delta^{13}\)C (Figure 2F), and a significant positive linear relationship between \(A\)/\(g_{\mathrm{s}}\) and \(\delta^{13}\)C (Figure 2E). \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c c c c c c} \hline \hline \multicolumn{11}{c}{**Year 2020**} & \multicolumn{1}{c}{**Year 2020**} & \multicolumn{1}{c}{**Post-version period (August-September)**} & \multicolumn{1}{c}{**OGenerally speaking, taking into account the average of two years, \(\gamma\)s was not significantly affected by water stress, except for two clones (4 and 276), which showed a signif  
Figure 2: (**A**) Relationship between average _A/S\({}_{5}\)_ measured from fruit set to harvest in the morning, and productive WUE in 2020. (**B**) Relationship between average _A/S\({}_{5}\)_ measured from fruit set to average in the morning and midday, and yield at harvest in 2020. (**C**) Relationship between average _A/S\({}_{5}\)_ measured in the morning at pre-veraison period, and productive WUE (WUE\({}_{\rm yield}\)) in 2021. (**D**) Relationship between average _A/S\({}_{5}\)_ measured in the morning at pre-veraison period, and yield in 2021. (**E**) Relationship between average _A/S\({}_{5}\)_ measured during the whole season (pre- and post-veraison period, early morning and midday) and carbon isotopic _A/S\({}_{5}\)_ in berries in 2020. (**F**) Relationship between yield at harvest and carbon isotopic _A/S\({}_{5}\)_ in berries in 2020. (**G**) Relationship between WUE\({}_{\rm yield}\) and carbon isotopic _A/S\({}_{5}\)_ in berries in 2020. Each point represents the measurement in a single vine for the different clones and under control and stress conditions. *, indicate significant differences at the 0.1 levels of probability. icantly higher \(\Psi\)s under water stress compared to their controls (Figure 3A). In the other, \(\Psi\)s did not change substantially under water stress compared to the control.