Preliminary Assessment of Stomatal Regulation in Vitis vinifera L. cv. País from Contrasting Provenances Under Water Deficit

Water scarcity increasingly threatens viticulture, yet the drought-response strategy of patrimonial cultivars such as País remains poorly characterized. This study evaluated intra-cultivar variation in the drought response of three País provenances from northern Chile (Arica, Huasco, and Limarí), using Cabernet Franc as a reference cultivar. The experiment was conducted under semi-controlled pot conditions at the Limarí Campus of the University of La Serena, Ovalle, Chile, using a completely randomized design (n = 5). Plants were subjected to a four-week dry-down followed by rewatering. Relative pot water content, stem water potential, and stomatal conductance were monitored, and stomatal thresholds (Pg12, Pg50, and Pg88) were estimated from nonlinear vulnerability curves. Water deficit reduced plant water status and stomatal conductance. Cabernet Franc maintained the highest maximum stomatal conductance, whereas País showed a more conservative stomatal pattern. Within País, Pg50 differences were weakly supported and model-dependent: Huasco tended to reach 50% stomatal reduction at more negative stem water potentials than Arica and Limarí, while Pg12 and Pg88 largely overlapped. After rewatering, stem water potential recovered faster than stomatal conductance, particularly in Arica and Limarí. These results indicate that drought-response variation in País reflects provenance-specific stomatal regulation and recovery rather than source-site aridity alone.