Changes in parameters of the plasmalemma ATPase during peach vegetative bud dormancy

Plant dormancy and dormancy breaking depend, at least partially, on close r elationships between buds and tissues underlying bud (bud stands). In Prunu s persica, the dormancy was related to high nutrient absorption in bud stan ds linked to high plasmalemma ATPase (EC 3.6.1.3) activity. Two plasmalemma fractions was isolated fi om peach vegetative buds and bud stands using aq ueous phase partitionning and ultracentrifugation. Results of markers enzym e assays indicated that both plasmalemma enriched fractions obtained were h ighly purified. During the dormancy period plasma membrane ATPase amount an d activity were higher in bud stands than in buds. Moreover, assays perform ed at different temperatures (4, 18, 30 degrees C) indicated modifications of kinetic parameters (K-m, V-m) in both tissues during dormancy release. I n buds, from November to February, K-m, declined at 4 degrees C and increas ed at 30 degrees C whereas no changes was measured at 18 degrees C and V-m increased at all temperature. In bud stands, no changes of K-m was measured at 4 degrees C and 18 degrees C whereas an increase occurred at 30 degrees C and V-m decreased at all temperature. According to the results, it can b e postulated that dormancy release in peach-tree could be related to modifi cations of plasma membrane ATPase properties, in buds and bud stands, durin g winter time.