The objects of research were silver birch (Betula pendula Roth var. pendula) and Karelian birch (B. pendula var. carelica). The result of our previous studies have led to the conclusion that the cause of the structural abnormalities of Karelian birch is excessive content of sucrose in the conducting phloem and cambial zone. Since only transport sucrose can influence on the morphogenesis it is necessary to form a correct estimate of sucrose pool, its transport and storage components.
The present study has shown that sucrose is the basic transport form of assimilates both in silver birch, and in Karelian birch. Sucrose is present in birch only at the transport form, it doesn't carry out storage function; storage of sugars occurs in the form of fructose.