SummaryCommercial tree fruit nurseries can promote aggressive tree growth by adding greater amounts of N than is necessary. Although this practice may produce the largest stock possible, it often causes physiological problems such as delays in growth cessation, bud dormancy development, and cold acclimation, especially in late apple cultivars. In this study, abscisic acid (ABA) was applied to Fuji/M.26 apple (Malus domestica Borkh.) nursery plants that had been growing into the late season with a high N supply. We tested the hypothesis that exogenously applied ABA enhances growth cessation and that this is related to the improvement of bud dormancy development and cold acclimation. We also studied the effects on leaf senescence and mobilization of leaf N into perennial woody tissues. In September 1996, ABA at 1000.mg l-1 plus 0.1% Tween 80 was sprayed twice, at 7.d intervals. ABA treatment significantly enhanced shoot growth cessation and advanced the early stages of bud endodormancy development; these effects were closely related. Maximum growth cessation and bud dormancy were attained in mid-December similarly in both control and ABA treatments. In early November, stem cold hardiness measured by the electrolyte leakage method was significantly greater in the ABA-treated plants than in the controls, but was similar in late December. This indicated that cold acclimation was related to the depth of bud endodormancy development. N mobilization from the senescing leaves into perennial woody tissues was significantly enhanced by ABA treatment. Therefore, autumnal increases in total-N and soluble-protein concentrations were significantly higher in the ABA-treated plants (especially in the stem bark), but both control and ABA-treated plants reached similar maximum levels later when plants were completely defoliated.