IntroductionTable grapes are very sensitive to fungal decay and water loss,both causing substantial postharvest losses. Susceptibility to dis-ease and water loss is particularly dependent on the cuticularbarrier and the condition of the underlying epidermal cells inthe skin (Boyer et al., 1997; Comménil et al., 1997). The centralvacuole of grape berry cells plays an important role in main-taining their volume, and in controlling the gradients of vacuolarion concentrations that are essential for acid and sugar balancein the berry. Potassium is perhaps the most important ion ingrapes, playing an important role in controlling the vacuolar ionconcentration