Ontogeny and environment as determinants of the secondary chemistry of three species of white birch.

This study investigates variation in the secondary chemistry of the bark of three closely related, winter-dormant species of white birch (Betula resinifera, B. pendula, and B. platyphylla) at different ontogenetic stages by using different plant parts (top and base). The experimental birches were grown for 4 years in two growing conditions (pot and field) at different nutrient levels. There was considerable species-specific quantitative and qualitative variation in the secondary chemicals in bark, but this was also affected by fertilization and the age of the plant. In general, there was greater chemical diversity in saplings than in seedlings. The study revealed three new components, secoisolariciresinol 9-O-beta-glucopyranoside and two of its derivatives, that have not been reported previously for the bark of white birches. Principal component analysis showed that the species studied had a similar chemical composition at the juvenile stage, but as the plants grew, they became more clearly differentiated, which indicates that the species of older plants can be identified by chemotaxonomy. Evidently, the secondary chemistry of birches is under genetic control, but it is affected by properties of growing conditions and ontogeny.