## 4 Discussion
### Clones Show Different Hydraulic Behavior, Stomatal Regulation, and Vine Water Use
However, it is also noticed that for the same value of \(g_{s}\), (overall at high \(g_{s}\)), maintaining a lower \(A\) and a higher \(Ci\) (clone 4), compared to higher \(A\) and lower \(Ci\) (e.g., clones 276, 372) (Figure 8), would indicate a higher photosynthetic efficiency in low-vigor clones (276, 372) than in clone 4, which can adapt their photosynthetic machinery to maintain high and fairly constant CO\({}_{2}\) partial pressure inside the leaf. A decreased \(g_{s}\) as a consequence of water stress increased \(A\)/\(g_{s}\) differently depending on the clone (Figure 8D). This \(g_{s}\) vs. \(A\)/\(g_{s}\) relationship may provide the sensibility of each clone to water deficit according to the slope of the linear regression obtained from this relationship; thus, a lower slope means a lower sensibility of the clone to water deficit [12]. Therefore, clone 4 had a lower slope (\(-\)200.87, data not shown) and was less sensitive to water deficit than clones 276 (\(-\)437.63) or 372 (\(-\)383.08), which were the most sensitive clones to water deficit (Figure 8D). This was also supported by a higher berry \(\xi^{13}\)C (less negative) and transpiration use efficiency (\(A\)/\(E\)) (assimilation per unit water transpired) in low-vigor clones (Table 3). Consequently, it appears that the low-moderate vigor genotypes may improve transpiration use efficiency as well as the expected reduction in total transpiration due to the lower canopy size [71]. Interestingly, Monastrell clones also differed in their response to atmospheric VPD (Figure 7). Therefore, \(E\) became more responsive to VPD as the water stress intensified. This led to a progressive change in the response of \(E\) to VPD, from a greater increase of \(E\) at a high VPD in control plants (higher VPD drove \(E\) when stomata were open) to a lower increase in \(E\) at a high VPD in water stressed plants, mainly in clone 276, followed by 372 (the most drought-stress responsive clones) (Figure 7), as previously found in other grapevine varieties [72; 73]. Low-Vigor/Productive Clones Enhance Berry and Wine Quality and Aromatic/Nutraceutical Potential Compared to High-Vigor/Productive Clones  
It has been reported that, traditionally, high vine vigor and yields are associated with grapes and wines of low quality [74]. In this way, high-vigor and productive clones 4 and 94 gave the highest berry weight, but a poorer final berry technological and phenolic quality (lower QI scores), mineral content, and color intensity in the must and wine compared to other clones, and this may, in part, have been due to a greater dilution phenomenon (lower skin/pulp ratio and higher % juice and H\({}_{2}\)O in 2021). In addition, a higher acid malic concentration in the berries from high-vigor clones (specially in clone 4, Table 6) could be due to a higher leaf area development and lower cluster exposure to direct solar radiation and, as a consequence, lower berry temperature, decreasing malic acid degradation [75]. In contrast, the most water stressed clone was the least productive and vigorous one (clone 360) and showed the highest SM index, concentration of YAN, mineral content, and tannins, in addition to higher QIs (berry quality indices) in the must (Tables 6-11) than the rest of clones. This was probably due to a greater concentration effect as a consequence of a significantly lower berry weight/size (higher skin/pulp ratio), lower must and H\({}_{2}\)O percentages, and modifications in grape microclimate [20] (Tables 5, 6 and 10). Despite a greater WS, clone 360 had a higher concentration of YAN, above 180 mg L\({}^{-1}\), which may be positive for aromatic precursor concentrations in must and in aromas in wines [69]. Nevertheless, a greater tannins concentration and SM index (that measures the contribution of seeds to the total amount of polyphenols, mainly tannins from seeds), as also observed in clone 360, would indicate a higher risk of a negative effect on the flavour of the wine (e.g., a greater sensation of astringency or bitterness) [30].