Young “Riesling” grapevines were induced to produce second shoots by water stress before summer pruning. The vines, field-grown and established in isolated soil beds were subjected to water stress by disconnecting irrigation for 15 and 23 days. Water stress enhanced budbreak and cluster formation. In the early stage of water stress, abscisic acid (ABA) content increased in the canes and trunks, while it decreased in the roots. As the stress persisted, ABA content dropped in the canes and trunks, but increased in the roots. The levels of nitrogen, amino acids, and soluble sugars in the canes, trunks, and roots increased during water stress, while the levels of starch decreased. The results were discussed in relation to interactions of ABA with metabolism of amino acids and sugars. A high level of ABA during water stress was proposed to play a role in stimulating nutrient accumulation. A high reserve of nutrients, being available upon resumption of watering, was proposed to stimulate budbreak and subsequently to improve flower formation.