Changes in Parameters of the Plasmalemma ATPase during Peach Vegetative Bud Dormancy

Plant dormancy and dormancy breaking depend, at least partially, on close relationships between buds and tissues underlying bud (bud stands). In Prunus persica, the dormancy was related to high nutrient absorption in bud stands linked to high plasmalemma ATPase (EC 3.6.1.3) activity. Two plasmalemma fractions was isolated from peach vegetative buds and bud stands using aqueous phase partitioning and ultracentrifugation. Results of markers enzyme assays indicated that both plasmalemma enriched fractions obtained were highly purified. During the dormancy period plasma membrane ATPase amount and activity were higher in bud stands than in buds. Moreover, assays performed at different temperatures (4, 18, 30 °C) indicated modifications of kinetic parameters (Km, Vm) in both tissues during dormancy release. In buds, from November to February, Km declined at 4°C and increased at 30 °C whereas no changes was measured at 18 °C and Vm increased at all temperature. In bud stands, no changes of Km was measured at 4 °C and 18 °C whereas an increase occurred at 30 °C and Vm decreased at all temperature. According to the results, it can be postulated that dormancy release in peach-tree could be related to modifications of plasma membrane ATPase properties, in buds and bud stands, during winter time.