INFLUENCE OF DIFFERENT NUTRIENT REGIMES ON THE REGULATION OF CARBON METABOLISM IN NORWAY SPRUCE [PICEA-ABIES (L) KARST] SEEDLINGS

Phosphoenolpyruvate carboxylase (PEPC) activity, fructose 2,6-bisphosphate (F26BP), starch and soluble sugar contents were determined in needles and roots of Norway spruce seedlings grown in a semi-hydroponic cultivation system under different nutrient regimes. In needles, a surplus of nitrogen caused an increase in specific PEPC activity (up to six times control activity) and F26BP content (up to three times control level) while starch content was reduced. Sucrose contents were not affected. Basically, the responses in root samples were similar. Here, PEPC was highest at an imbalance in nutrition (+N/-P). F26BP, with root contents being 3- to Ii-times higher than those in needles, significantly exceeded control values at +N/+P. The results show that alteration of nitrogen supply leads to marked changes in allocation of carbon between pathways, which is also influenced by P-nutrition. Pool sizes of F26BP and activity of PEPC are indicators for these changes in leaf as well as in root tissues of Norway spruce.