Differences in Cell Development in Three Species of Conifers Growing in Equal Exogenous Conditions in Eastern Siberia

To assess the reaction of trees, including conifers, which differ in the physical and mechanical properties of wood, to external factors, it is especially important to study the development of phloem and xylem cells and the deposition of biomass in tree trunks growing in the same exogenous conditions. The phenology of the cambium, the development of phloem and xylem cells and the deposition of biomass in wood annual layers in the trunks of Scots pine, Siberian larch and Siberian spruce, growing under the same exogenous conditions in Eastern Siberia, were studied. It was shown that during ontogenesis each species demonstrated its own seasonal dynamics of cambium activity in the production of phloem and xylem cells and the accumulation of biomass in tracheids walls. Of the three species studied, the largest number of cells produced by the cambium was found in larch. Spruce had the least activity in terms of these growth characteristics. During periods of maximum growth activity, the accumulation of biomass in the walls of larch xylem cells always exceeded these indicators in pine and especially spruce. The differences in xylogenesis of pine, larch and spruce are the consequence of species-specific features of their metabolism and its plasticity in response to changes in the external factors.