Annual dynamics of the content of non-structural saccharides in the context of structural development of vegetative buds of Norway spruce

Apical buds are very important organs as they determine further growth and development of tree species. Bud physiological state, including saccharide metabolism, determines their growth activity, and thus the development of the whole crown architecture. The present study focused on annual dynamics of the contents of non-structural saccharides (NSS) related to structural development in terminal vegetative buds of Norway spruce (Picea abies L. Karst.) during 1995. Two types of material were analysed: 1) four-year-old nursery-planted trees; and, 2) adult individuals from two mountain sites in the Czech Republic. Sugar and starch contents were determined, and starch was localised histochemically. Generally, the dynamics of the NSS content reflects the major morphogenetic and developmental changes occurring during the annual cycle. The highest content of sugars corresponds with a bud dormant state. Bud break is accompanied by the lowering of sugar content, reflecting the transition of buds to metabolically active sinks. During bud cold hardening in autumn, a massive gradual sugar accumulation takes place. The most pronounced change during the annual cycle is found in the content of raffinose, with the highest values observed during autumn and winter. The possible role of raffinose in bud frost tolerance is discussed. The results obtained from the buds sampled at the mountain sites are both qualitatively and quantitatively similar to the more detailed NSS-dynamics of young trees, thus, giving the justification to generalisation of the above described pattern for vegetative buds of Norway spruce.