water stress is the physiological state of plants, including vines, suffering from a shortage of water. Water stress during the later stages of the viticultural growing season is common, since a considerable proportion of the world’s vines are grown in mediterranean climates, where rain falls principally in the winter months and irrigation is restricted or not used. By the time of ripening, the amount of soil water may well be low. It is commonly held that mild water stress, often referred to as water deficit, is desirable for optimum wine quality, especially for red wines, but there is little agreement about exactly how much. There is, however, almost universal agreement that water deficit should be sufficient before veraison to stop shoot tips actively growing. Otherwise the shoot tips attract assimilates, the products of photosynthesis, away from the ripening fruit, to the detriment of wine quality.
