Effects of varied soil nitrogen supply on Norway spruce (Picea abies [L.] Karst.). II. Carbon metabolism in needles and mycorrhizal roots.

摘要

In a pot experiment in a N-poor forest soil, 3-year-old Norway spruce plants were given 0, 300 or 600 mg N/pot. Starch and sucrose contents in needles and roots decreased with increasing N. In addition, the activity and the protein amount of phosphoenolpyruvate carboxylase (PEPC) and the activity of NADP-dependent isocitrate dehydrogenase (IDH) were increased by N application. The activity of sucrose phosphate synthase (SPS) and the pool size of fructose 2,6-bisphosphate were not affected by N application. These data indicate a shift of carbon flow from starch formation towards an enhanced provision of carbon skeletons for N assimilation and shoot growth. In parallel, decreased contents of fungus-specific compounds (ergosterol, mannitol, trehalose) were found in roots, which are indicators of a decreased colonization by ectomycorrhizal fungi, probably as a result of a changed allocation and partitioning of photoassimilates due to an increased N supply.