Changes in nitrogen and polyamines during breaking bud dormancy in “Anna” apple trees with foliar application of some compounds

The capacity of hydrogen cyanamide (Dormex), potassium nitrate (KNO3) and mineral oil for breaking of dormancy in buds of “Anna” apple (Malus sylvestris, Mill) trees, and their effects on metabolic changes of nitrogen (N) and polyamines (PAs) in buds during bud break were determined. Our results showed that the capacity to release of buds from dormancy was noticed in varying degrees with these compounds. Breaking bud dormancy was correlated with the early date of bud break, the short duration of flowering, the high percentages of bud break and fruit-set, and the high contents of soluble N and PAs. The best results were obtained with Dormex; therefore we recommend using this compound for reaching the bud break as early as possible, the short period of flowering and the high percentages of bud break and fruit-set by regulating the contents of N and PAs in buds.

► Anna apple bud break maximized with Dormex foliar application.
► Dormex minimized flowering duration under Egyptian winters.
► Polyamines significantly improved in buds treated with Dormex.
► Polyamines play an important role in bud release from dormancy.