Metabolic Changes in Polyamines, Phenylethylamine, And Arginine During Bud Break in Apple Flower Buds Under Foliar-Applied Dormancy-Breaking Agents

The Environmental and climatic conditions affect the flower bud growth, flowering and yield performance of fruit species. Temperature appears to be important factors for temperate fruit trees in mild climates. The relationships between breaking bud dormancy and climatic influences on flowering, growth and metabolic changes in contents of biogenic amines (spermine, spermidine, putrescine, cadaverine and phenylethylamine), arginine and anthocyanin before and after bud break were evaluated for "Ain Shemer" apple (Malus sylvestris, Mill) trees under exogenously applied hydrogen cyanamide (dormex), calcium nitrate Ca(NO3)2 and thiourea. The studies have shown that breaking bud dormancy (as early date of bud break and percentage of bud break) by the above dormancy breaking agents were correlated with the high content of biogenic amines and arginine in buds. Seasonal variations in biogenic amines, arginine and anthocyanin level were present in buds during the research period (dormancy and dormancy release period). Levels of spermine, spermidine, putrescine, cadaverine, phenylethylamine, arginine and anthocyanin have simultaneously risen with bud burst and new growth. The most abundant polyamines in buds were cadaverine followed by spermine. The best results were obtained with Dormex after exposure the trees to about 274 natural chilling hours ? +7.2oC; therefore, we recommend using this compound to achieve bud break as early as possible in "Ain Shemer" apple variety by regulating the contents of biogenic amines and arginine in buds and subsequently the high percentages of bud break and maximum yield.