Betula resinifera

Triterpenes (C30) are common in birches, especially in bark. Papyriferic acid from paper birch, Betula resinifera, is a feeding deferent for snowshoe hares, Lepus americanus Big. 11.5) (Reichardt etal, 1985). 

However, not all related species or conspecific populations respond similarly under the same UV influence. For example, Betula pendula and B. resinifera, two closely related birch species collected from populations in Europe and Alaska, generally produce a number of flavonoids, hydroxycinnamic acids, and condensed tannins in larger quantity in exposed leaves to artificial UV-B photon fluxes (4.9 kJ m d for 3 hr/day of biologically active radiation) than in non radiated plants (Lavola, 1997). In B. pendula populations the major increase was in flavonoid synthesis but in B. resinifera the bias was towards the hydroxycinnamic acids and condensed tannins. Besides, allopatric (geographically distant) populations of birch reacted differently in the synthesis of specific compounds. For example, chlorogenic acid increased by 22 and 92% in plants from Germany and Alaska, respectively, but in Finnish plants there was no increment at all. 

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