Regulation of Bud Rest in Tubers of Potato, Solanum tuberosum L: VIII. Early Effects of Gibberellin A(3) and Abscisic Acid on Ultrastructure.

Using the electron microscope, we compared the effects of abscisic acid and gibberellin A(3) on excised buds from resting potato (Solanum tuberosum L.) tubers. Cells of abscisic acid-treated buds became progressively more vacuolated during a 12-hour time course study as compared with control (water) and gibberellin A(3)-treated buds. Concentric configurations of endoplasmic reticulum were present in apical cells of freshly excised buds. After about 6 hours these configurations began to open and disperse, and after 12 hours, intact concentric configurations were no longer evident. Both abscisic acid and gibberellin A(3) induced opening and dispersal of the concentric configurations, sometimes as early as 0.5 hour after excision and treatment with hormones.