DIFFERENTIAL-EFFECTS OF POTASSIUM AND MOLYBDENUM DEFICIENCY AND FERTILIZATION ON NITROGEN-METABOLISM IN NORWAY SPRUCE (PICEA-ABIES)

A field study on mineral nutrition of 12 year old Norway spruce (Picea abies (L.) Karst.) was carried out on a Lower Triassic region in the Eifel mountains in a plantation where the juvenile trees exhibited mar ked visual differences on adjacent plots, thus indicating a patchy pat tern concerning the fertility status of the soil. This was confirmed b y geological, pedological and chemical analyses, including X-ray diffr action analyses of the clay minerals and soil water as well as needle element analyses. A combined K and N deficiency was diagnosed for thos e trees, which exhibited growth retardation and small, rigid, and yell owish-green needles. Chlorophyll and protein content and glutamine syn thetase activity were reduced while triphenyltetrazoliumchloride (TTC) reduction was enhanced in the sick trees as compared to adjacent heal thy looking trees of the same age and provenance. A diagnostic fertili sation treatment with K and Mo, respectively, yielded the following re sults. One year after administration of Mo a marked increase in total N content of the needles was observed, due to an increase of the stora ge pools for soluble (nonprotein) nitrogen, namely the basic amino aci ds arginine, histidine and lysine and also of ornithine. Yet, no visua l recovery of the trees was observed. On the other hand, K fertilizati on caused an improvement of all biochemical parameters, except protein content and soluble N storage pools. The relationships between Mo dep endent nitrate reduction, potassium content and nitrogen metabolism ar e discussed.