THE NITROGEN METABOLISM OF PICEA GLAUCA (MOENCH) VOSS AND PINUS BANKSIANA LAMB. AS INFLUENCED BY MINERAL NUTRITION

Abstract

White spruce (Picea glauca (Moench) Voss) and jack pine (Pinus banksiana Lamb.) seedlings were grown in sand cultures by Swan (who reported on their growth in 1960) and they were irrigated with full nutrient solution high in sodium, or solutions deficient in each of several nutrients. Responses characteristic of the following six treatments were studied: full nutrient but with low sodium; nitrate or ammonium as the sole source of nitrogen; low nitrogen; low phosphorus; and low potassium. When shoot elongation had ceased, extracts of seedling parts (leaves, stems with buds, and roots) were examined by paper-chromatographic methods for free nitrogenous compounds.In leaves, the relative proportions of nitrogenous compounds in spruce and pine differed from those in the stems and roots. Nutrient deficiency and the form of nitrogen available affected both the total amount and relative composition of the soluble nitrogen. Under better mineral nutrient conditions, arginine accumulated while amide (glutamine) remained low. The accumulation of a number of compounds resulting from nutritional deficiency, for example glutamine, with low potassium, indicated that blocks occurred in metabolic pathways. Ammonium nitrogen was shown to foster arginine and amides (especially in spruce) and to lead to a large increase of free guanidino compounds which hitherto have passed unnoticed. By contrast, in leaves nourished by nitrate as the sole source of nitrogen, guanidino compounds were less prominent. Under the conditions of reduced growth and protein synthesis brought about by specified nutrient deficiencies, many unidentified compounds, which were not known intermediates of the ornithine or urea cycle, appeared.The present study dealt with observations made at one season of the year (late summer) and does not preclude the occurrence of somewhat different responses which might have been observed at other times of the year.