Ammonium and nitrate as nitrogen sources in two Eriophorum species

Summary 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 M, 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.