Ammonium and nitrate as nitrogen sources in two Eriophorum species

We compared ammonium and nitrate nutrition in Eriophorum scheuchzeri and E. vaginatum, two Alaskan sedges that are native to high- and low-fertility sites, respectively. When grown in solution culture, the two species were similar in their kinetics of NH _inf4^sup+ NO _inf3^sup- absorption: at nitrogen concentrations below 50 μM, net NH _inf4^sup+ and NO _inf3^sup- were absorbed at similar rates, but at higher concentrations, net uptake of NO _inf3^sup- was significantly faster than that of NH _inf4^sup+ . The two species also showed similar abilities to assimilate NO _inf3^sup- . Growth of E. vaginatum under NO _inf3^sup- nutrition was only slightly less than that under NH _inf4^sup+ . The observed similarities between these species from contrasting edaphic habitats indicate that factors other than tissue-specific rates of nitrogen acquisition and assimilation may underlie local adaptation to soil N fertility. Moreover, the capacity of these species to exploit NO _inf3^sup- as a N source supports the view that NO _inf3^sup- availability may be significant even in wet, acidic, arctic soils.