SEASONAL DYNAMICS OF ARGININE CONTENT IN PINUS SYLVESTRIS L. NEEDLES DEPENDING ON THE TIM-ING OF NITROGEN AND BORON APPLICATION

Abstract

The annual cycle of arginine content in young and 1-year-old needles of 10-year-old Scots pine (Pinus sylvestris L.) was studied as related to various periods of nitrogen deposition into the soil at a high dose (300 kg/ha) and boron deposition in the optimal dose (3 kg/ha). Fertilizers were applied once, in June, July or August. The amino acid levels in young and 1-year-old needles of control plants remained similar throughout the study period (0.7±0.1 – 1.3±0.1 µmol/g absolute dry matter), with the peak in May. The placement of the fertilizers in the soil at three instances considerably augmented arginine content in young and 1-year-old needles during the first annual cycle following the impact. Nitrogen and boron application to the soil in June had the highest effect on arginine accumulation, primarily in young needles. The maximum amino acid levels were 618 ± 60 and 152 ± 15 μmol/g DM, 256 ± 24 and 154 ± 14 μmol/g DM, 132 ± 13 and 76 ± 7 μmol/g DM at the June, July and August fertilization in the young and 1-year-old needles, respectively. The seasonal patterns of arginine accumulation in coniferous plants, as well as the mechanisms through which nitrogen and boron influence this process are discussed.