Xylogenesis, photosynthesis and respiration of Scots pine trees growing in Eastern Siberia (Russia)

Abstract Key message The relationships between cambium activity, cell wall biomass accumulation and photosynthesis/ respiration in Scots pine trees, growing in Eastern Siberia (Russia), change during the season in dependence on combination of summer-weather conditions. The wood formation in tree trunks depends on photosynthesis and respiration and the each of the processes are under the effect of external factors. Each factor effects the growth in combination with other factors and the change in any of these factors leads to strengthen or to weaken of the growth processes in tree. We investigated the formation of xylem and phloem cells by cambium, cell wall biomass accumulation in Scots pine trees, growing in Eastern Siberia (Russia), in dependence on the productivity of photosynthesis and energy cost in separate seasonal periods in the years with opposite summer-weather conditions. The cores extracted throughout 10-day from the stems of 10 trees during the seasons were used to determine the number of cells with different development degree and their morphological parameters. Cambium activity and cell wall biomass accumulated on the separate stages of annual ring wood formation and their connections with the photosynthetic productivity of crown and the level of stem respiration photosynthesis were assessed. The activity of cambial cell division into xylem or phloem sides in separate periods depended on the combination of temperature/precipitation and on the connection with photosynthesis and respiration. The dynamics of biomass accumulation was bimodal with the maximums in June (earlywood development) and mainly in August (development of thick-wall late tracheids), what was due to the combination of optimal temperature and the moisture in the stem tissues. The variation in the external factors changed the balance between the incoming of photoassimilates and the energy cost causing a competition for photosynthesis products and, as a consequence, photoassimilates were used not only for cell-wall biomass synthesis and but also for their reservation of spare substances in the form of starch. The data is useful to understanding of internal processes of wood annual ring formation in pine trees.