Environmental factors affecting basic nitrogen metabolism and seasonal levels of various nitrogen fractions in tissues of bilberry, Vaccinium myrtillus

Bilberry tissues accumulated nitrogen for the winter in the form of reduced low-molecular weight amino compounds. The storage organ was principally the underground stem and the oldest parts of the aerial shoot. Most of the nitrogen was stored in arginine and ammonium compounds, and less in glutamine and other amino acids. Proteins did not accumulate during the winter. The soluble nitrogenous compounds were discharged from storage in May, when nitrogen was translocated from the lower parts of the stem to the growing leaves and buds. Amino acid compositions and concentrations in winter were almost identical under the snow and in snowless areas, only the concentration of glutamine being lower and that of glutathione higher in the snowless area. The level of total protein, particularly in the leaves and buds was much higher in a nitrogen-polluted industrial area than in unpolluted urban forests. The same difference was observed in total amino compounds, but among individual substances it only appeared in ammonium compounds. Certain species differences in the amino acid pool were recorded between V. myrtillus and V. vitis-idaea.