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-bisphosp hate (F26BP), starch and soluble sugar contents were determined in nee dles and roots of Norway spruce seedlings grown in a semi-hydroponic c ultivation system under different nutrient regimes. In needles, a surp lus of nitrogen caused an increase in specific PEPC activity (up to si x times control activity) and F26BP content (up to three times control level) while starch content was reduced. Sucrose contents were not af fected. Basically, the responses in root samples were similar. Here, P EPC was highest at an imbalance in nutrition (+N/-P). F26BP, with root contents being 3- to Ii-times higher than those in needles, significa ntly exceeded control values at +N/+P. The results show that alteratio n of nitrogen supply leads to marked changes in allocation of carbon b etween pathways, which is also influenced by P-nutrition. Pool sizes o f F26BP and activity of PEPC are indicators for these changes in leaf as well as in root tissues of Norway spruce.