Effects of Water Deficit on Water Fluxes and Sugar Content in Grape Berries

This article summarizes key physiological and molecular processes that regulate water and sugar transport in grape berries and analyzes the effects of water stress on these mechanisms. Water deficit reduces yield by limiting both berry number and size, with floral initiation in year N–1 and flowering/fruit set in year N governing these outcomes. Pre-veraison berries show marked diurnal shrinking under drought, whereas post-veraison berries, largely disconnected from the mother plant, contract only slightly. The duration and timing of stress further modulate sugar accumulation, influencing berry quality under climate change.