Physiological Thresholds for Efficient Regulated Deficit Irrigation Management in Winegrapes under Semiarid Conditions: Soil-Plant-Water Relationships and Berry Composition

This work shows that Regulated Deficit Irrigation (RDI) applied during pre-and post-veraison periods offers a great potential to improve phenolic composition and increase water use efficiency in vineyards under semiarid conditions. However, an efficient irrigation scheduling of RDI requires also that soil and vine water status to be maintained accurately within a defined tolerance range in order to avoid deleterious effects in the vines and in the berry composition. In this study we have identified different thresholds values and optimum ranges of some important physiological parameters, such as, stem water potential, Psi(s) (between -1.3 and -1.4 MPa, never Psi(s)<=-1.4 MPa), photosynthesis rate (between 10 and 12 mu mol m(-2) s(-1)), stomatal conductance (between 0.12 and 0.15 mol m(-2) s(-1)) and gas exchange efficiency (A/g(s) around 85-90 mu mol mol(-1)). According to the relationships found between the physiological status of the vine and berry composition at harvest, to maintain during pre-and post-veraison periods the levels of these parameters within these ranges of threshold values proposed, could be used as physiological tool to improve berry quality (mainly phenolic composition) and irrigation management in RDI 'Monastrell' grapevines under semiarid conditions.