Carbohydrate Accumulation in Siberian Spruce Needles of Various Ages

The content of mono- and oligosaccharides, hemicelluloses, and water-soluble polysaccharides was studied in Siberian spruce (Picea obovata Ledeb.) needles of various ages. Accumulation of carbohydrates during the growth period and the ratio of their individual fractions were determined by the proportions between the growth rate and assimilate export in developing needles. Throughout the growth period, the content of monosaccharides in needles of all ages was much higher than that of oligosaccharides. Unlike the period of active growth, the dormancy period was characterized by a wider diversity of oligosaccharides and their rather high content. Hemicelluloses that accumulated during the previous growth season and water-soluble polysaccharides of 2- and 3-year-old needles were involved into metabolism at the time of active growth of current-year needles. Analysis of carbohydrate accumulation in 1- to 9-year-old needles showed that the monosaccharide concentration was higher in needles of the first two years. The content of hemicelluloses A and B and water-soluble polysaccharides was higher in older needles. During the growth period, the assimilates of 2- and 3-year-old needles were partly used for the formation of young needles. The increase in relative content of polysaccharides during needle senescence reflects the involvement of photosynthetic products into the secondary pool of carbon metabolites.