Ways of adaptation the secondary xylem of woody plants to the extreme environment of the Arctic region

Woody plants of the Arctic floristic region can be considered as an anomalous phenomenon, but on the other hand - as an usual biomorphs adapted to the extreme environment of high latitudes. Their formation with advancement toward the North is assotiated with a certain trend of morphological and microstructural changes and in particular wood which has some common features with anomalous structures: reduction the length of cambial initials, increase the volume of parenchyma (especially of radial rays), wavy growth of elements and so on. However, the secondary xylem of such dwarf shrubs has its own specific features: small cells and thin walls in all the elements, high level of their structural and functional correlation, a diversity of tracheal structures. Study of regularities of definitive xylem formation of the researched species convinces us that in the extreme environment conditions of the Arctic the abnormal growth of dwarf shrubs and prostrate dwarf shrubs becoming the norm and represent one of the ways of adaptation.