Biochemical characterization of early and late bud flushing in common ash ( Fraxinus excelsior L.)

Abstract

Ash is a fast growing hardwood tree producing crops of high quality timber. Young trees are susceptible to forking, caused by late spring frosts, which result in necrosis of the apical bud. The physiology of flushing buds has been investigated by quantifying variations of 14 different endogenous metabolites during progressive stages of bud development, from winter buds, swelling buds and flushing buds in the period March–June 2003. Oxidative products such as malondialdehyde or lipid peroxides, as well as polyamines, carbohydrates (hexoses, disaccharides, raffinose family of oligosaccharides) and sugar alcohols, presented variations directly related to the stages in bud development. An oxidative burst, and a polyamine transitory increase have been measured during bud development. The major feature of bud break and further bud development was a global decrease in the endogenous non-structural carbohydrates. In further studies, the bud-breaking responses of ash provenances with early and late flushing behaviour were recorded in shoots grown in controlled conditions and five metabolites (putrescine, mannitol, trehalose, sucrose and raffinose) showed significant differences between the provenances. Reduced levels of putrescine and increased levels of carbohydrates were recorded in late flushing provenances. Specifically, the content of mannitol, sucrose, trehalose and raffinose was significantly higher.