The Effect of Nitrogen Source on Growth, Nitrogen Economy and Respiration of Two High Arctic Plant Species Differing in Relative Growth Rate

Abstract

The effect of NH 4 + and NO 3 − on growth, nitrogen economy and respiration rates in two high arctic plant species differing in relative growth rate (RGR; Oxyria digyna and Dryas integrifolia), were investigated under controlled conditions. Dryas integrifolia, which is typically found in exposed, nutrient-poor habitats in the field, exhibited similarly low RGR values on the two nitrogen sources, with nitrogen treatment having no effect on its partitioning of biomass. In contrast, the species characteristic of more sheltered, fertile habitats, O. digyna, grew faster on NO 3 − than NH 4 + over much of the experimental period, due a greater net assimilation rate (NAR) and nitrogen productivity (NP). Nitrogen treatment had no effect on the leaf area ratio (or its components) of either species (...)