Dependence of Sap Flow and Stem Diameter Fluctuation of Grapevines on Reference Evapotranspiration: An Event Coincidence Analysis

The use of plant-based water status indicators is today very common because the plant itself is the best indicator of its water status, the data acquisition at a high resolution across larger temporal scale and its analysis is now more affordable, and plant water status controls many physiological processes and crop productivity, thus this information has great practical interest for crop management, in particular the water management. Grapes are widely cultivated worldwide but they are concentrated in Mediterranean type climates where water is scarce and face increased competition with other stakeholders. For these reasons but also because water influence vegetative growth and reproductive growth, yield and berry composition through their effects on berry size and on photosynthetic activity, vineyard water management has received great attention [1,2]. Vineyards managers try to maximize the water use efficiency at the cost of some reduction in crop yield that is not detrimental for the wine makers as the highest crop loads are linked to low grape quality, in fact, limitations to grape yield are a common practice for a market standard wine production and premium wines [3]. To determine the influence of environmental and cultural conditions on vine water use and the grapevine water status, and to manage water in the vineyard, one must use both a physiological indicator that integrates environmental conditions and tools to evaluate water use [4].