title: The ability of several high arctic plant species to utilize nitrate nitrogen under field conditions.
abstract: The ability to utilize NOinf3sup-in seven high arctic plant species from Truelove Lowland, Devon Island, Canada was investigated, using an in vivo assay of maximum potential nitrate reductase (NR) activity and applications of15N. Plant species were selected on the basis of being characteristic of nutrient-poor and nutrient-rich habitats. In all species leaves were the dominant site of NR activity. Root NR activity was negligible in all species except Saxifraga cernua. NOinf3sup-availability per se did not appear to limit NR activity of the species typically found on nutrient-poor sites (Dryas integrifolia, Saxifraga oppositifolia, and Salix arctica), or in Cerastium alpinum, as leaf NR activities remained low, even after NOinf3sup-addition.15NOinf3sup-uptake was limited in D. integrifolia and Salix arctica. However, the lack of field induction of NR activity in C. alpinum and Saxifraga oppositifolia was not due to restricted nitrate uptake, as15NOinf3sup-labelled NOinf3sup-entered the roots and shoots of both species. Leaf NR activity rates were low in three of the species typical of nutrient-rich habitats (O. digyna, P. radicatum and Saxifraga cernua), sampled from a site containing low soil NOinf3sup-. Additions of NOinf3sup-significantly increased leaf NR activity in these latter species, suggesting that potential NR activity was limited by the availability of NOinf3sup-.15N labelled NOinf3sup-was taken up by O. digyna. P. radicatum and Saxifraga cernua. Although two species (D. integrifolia and Salix arctica) showed little utilization of NOinf3sup-, we concluded that five of the seven selected high arctic plant species (C. alpinum, O. digyna, P. radicatum, Saxifraga cernua and Saxifraga oppositifolia) do have the potential to utilize NOinf3sup-as a nitrogen source under field conditions, with the highest potential to utilize NOinf3sup-occurring in three of the species typically found on fertile habitats.
authors.affiliation: Department of Botany, University of Toronto, L5L 1C6, Mississauga, Ontario, Canada.
authors.forename: Owen K
authors.initials: OK
authors.lastname: Atkin
authors.affiliation: Dept de Ecologia Facultad de Biologia, Apartado 1095, E-4180, Sevilla, Spain.
authors.forename: Rafael
authors.initials: R
authors.lastname: Villar
authors.affiliation: Department of Botany, University of Toronto, L5L 1C6, Mississauga, Ontario, Canada.
authors.forename: W Raymond
authors.initials: WR
authors.lastname: Cummins
keywords: 15N; Ammonium; Arctic plants; Nitrate; Nitrate reductase