Variability in water behavior during soil drought of different grapevine cultivars: new approaches to the internal regulation of water potential and stomatal control

Drought is considered to be the main environmental factor limiting crop growth and productivity worldwide; moreover, this problem will worsen in the coming years with the evolution of climate change. Better understanding how grapevine cultivars respond physiologically to water stress, beyond the traditional iso/anisohydry approaches, can be an essential tool to select the most suitable in each scenario. To achieve this objective, the evolution of water potentials (ψ_predawn and ψ_stem) and gas exchange (g_s and vpd_L) in six cultivars was studied during two consecutive summers as soil drought increased. The varieties were grown under the same conditions in an experimental vineyard, located at the Institute of Vine and Wine of Castilla-La Mancha (Tomelloso, Spain). Three different metrics were applied to generate the results: 1) the slope σ (linear relationship between ψ_predawn and ψ_stem); 2) a new 'hydroscape' approach and 3) another one that we have named 'conductance surface' and that we present for the first time in this communication. These new approaches seem to offer more consistent arguments for differentiating the drought response of different grapevine cultivars. Knowing how cultivars behave physiologically under water-limiting conditions, artificial intelligence technologies could be implemented in vineyard management to enable optimal decision making.