Development of a new chemical method for distinguishing between Betula pendula and Betula pubescens in Sweden
1995
Lundgren, L.N. | Pan, H. | Theander, O. | Eriksson, H. | Johansson, U. | Svenningsson, M.
High performance liquid chromatography (HPLC) analytical studies of inner bark extractives from a large number of silver birch (Betula pendula Roth) and hairy birch (Betula pubescens Ehrh.) trees revealed the diarylheptanoid glucoside platyphylloside to be present at high levels in B. pendula (20-60 mg/g dry bark) and at low levels in B. pubescens (50.5 mg/g dry bark). Based on these observations, a new simple and accurate precipitation method to distinguish between B. pendula and B. pubescens has been developed. In a solution of 2,4-dinitrophenylhydrazine, platyphylloside immediately forms an orange precipitate. A similar precipitate is also produced when a piece of B. pendula inner bark is kept for 1 h at room temperature in the same solution. However, no precipitate forms when a sample from B. pubescens is used. The diagnostic value of morphological characters was assessed by comparing the results of species determinations made on a large number of trees (> 1600), both juvenile and mature, using the morphological and the new chemical method. For birches younger than 20 years there was 100% agreement between the two methods. However, in some mature birch stands with the two species mixed and ages over 40 years, up to 20-30% of the trees were incorrectly identified to species using morphological characters. Results from tests using the precipitation method on birch species, varieties, forms, and hybrids were reported.
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