## 4 Discussion
### Consequences of Water Deficit on Pinot Noir Physiology and Berry Skin Anthocyanin Content
The maintenance of an adequate Kplant may have allowed SWE leaf to prevent stomatal closure and, consequently, an excessive restriction in carbon gain [71]. In addition, since the decline in Kplant is associated with hydraulic dysfunction, our results suggest that SWE leaf are less vulnerable to conduit embolism and collapse [56; 72; 73]. This effect could be particularly important in Pinot noir cv. which adopts an anisohydric strategy to cope with water stress, since anisohydric species are usually reported as more vulnerable to hydraulic failure [74]. The typical anisohydric behavior is evident from the slope (0.902) of the linear correlation between predawn and midday leaf water potential, which is close to 1 for extreme anisohydricspecies [75]. Our result suggests that _A. nodosum_ treatment could help maintaining a better water status of the plant preventing excessive stomatal closure without affecting the plant hydraulic strategy. The strong anisohydric behavior with great variations in leaf gas exchange and water relations during water stress progression could have been exacerbated by pot conditions, which imply the impossibility to access deeper soil water as in field conditions, where minor reductions in \(\Psi_{\text{leaf}}\) are usually observed [76]. However, controlled water stress conditions allowed us to validate the effect of _A. nodosum_ treatments on vine physiology previously documented in the field trial [46] and to highlight a timing of action of these treatments. Indeed, the effects of _A. nodosum_ treatments resulted particularly effective over the last part of the growing season, allowing treated plants to cope better with prolonged stress and leaf senescence. We hypothesize that the amino acids of the _A. nodosum_ extract, in particular proline, which is involved in drought tolerance acting both as cytoplasmic osmolyte and as ROS-scavenging compound [36; 37], may have played a key role in the enhancement of physiological performances and the maintenance of optimal water status. This mechanism could be particularly important under atmospheric stress conditions in adult leaves, which, differently from apical young tissues, are less able to accumulate actively solutes during the day and are subjected to oscillations of RWC [77]. These changes induced by _A. nodosum_ treatments on plant physiology did not have relevant consequences on berry ripening, indeed the evolution of total sugars, titratable acidity, and pH were unaffected by _A. nodosum_ treatments. This observation is in agreement with the results obtained by [PERSON] et al. [49; 50], but it is somewhat contrasting with the previous observations conducted in field conditions [46]. This discrepancy could be related to multiple factors, such as biological (cultivar, rootstock), methodological (pot or field studies), and environmental (season) factors, which may influence grape ripening pattern [78]. In addition, berry weight and vine productivity (data not shown) were not affected by medium-late _A. nodosum_ extract applications. Conversely, biostimulant applications during early stages of berry development could lead to an improvement in berry weight and vine yield, as formerly mentioned for table grape [41; 42; 43; 44]. A. nodosum Treatments Influenced the Biosynthesis of Berry Skin Anthocyanins Irrespective of Irrigation Regime  
The _A. nodosum_ treatment induced higher content of delphinidin, petunidin, cyanidin, and peonidin derivatives under both irrigation regimes both at t\({}_{1}\) and at t\({}_{2}\). This treatment-induced increment of anthocyanins in _Vitis vinifera_ is consistent in both pot and field conditions [46; 50] and is reported also in other species [79; 80; 81]. In addition, we observed a reduction of the methoxylated to nonmethodoxylated anthocyanin ratio and of the percentage of methoxylated anthocyanins on total anthocyanins in berry skin induced by _A. nodosum_ treatments.