Induction of nitrate uptake and nitrate reductase activity in trembling aspen and lodgepole pine

Abstract

13NO3- influx into the roots and in vivo nitrate reductase activity (NRA) in the roots and leaves have been measured in trembling aspen (Populus tremuloides Michx.) and lodgepole pine (Pinus contorta Dougl.) seedlings after exposure to either 0.1 or 1.5 tool m-3 NO3- for varying periods up to 20 d. Both NO3- influx and NRA were inducible in these species and, in trembling aspen, peak induction of nitrate influx and NRA were achieved within 12 h, compared to 2-4 d for influx and 4-12 d for NRA in lodgepole pine. In trembling aspen, ≃ 30% of the total 13N absorbed during a 10 rain influx period followed by 2 min of desorption was translocated to the shoot. In lodgepole pine, by contrast, trans..