Phytohormones as indicators of the degree of damage in birch (Betula pendula)

In the study of, the cyclophysis of birch (Betula pendula Roth.) a higher e thylene production and decrease of ethane production were found during budb reak and growth of one-year-shoots. After the beginning of endogenous dorma ncy in August, ethylene production was decreased while ethane production an d the level of abscisic acid increased. One-year-shoots from heavily damaged birch stands produced significantly mo re ethylene, simultaneously with lower ethane production and revealed lower content of abscisic acid in buds at the dormancy onset compared to one-yea r-shoots from the stands which were not exposed to stress load. The stresse d birches according to the degree of damage produce lower amounts of ABA in response to stress (cold stress in April) and during dormancy onset. In co ntrary, at the end of the dormancy the level of ABA in undamaged birches de creased to the lowest level. One-year-shoots from stressed stands showed si gnificantly lower redox potential than those from the undamaged control sta nds.