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 t he whole crown architecture. The present study focused on annual dynamics o f the contents of non-structural saccharides (NSS) related to structural de velopment in terminal vegetative buds of Norway spruce (Picea abies L. Kars t.) during 1995. Two types of material were analysed: 1) four-year-old nurs ery-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 refle cts 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, reflectin g the transition of buds to metabolically active sinks. During bud cold har dening in autumn, a massive gradual sugar accumulation takes place. The mos t pronounced change during the annual cycle is found in the content of raff inose, with the highest values observed during autumn and winter. The possi ble role of raffinose in bud frost tolerance is discussed. The results obta ined from the buds sampled at the mountain sites are both qualitatively and quantitatively similar to the more detailed NSS-dynamics of young trees, t hus, giving the justification to generalisation of the above described patt ern for vegetative buds of Norway spruce.