Ammonium and nitrate as nitrogen sources in two Eriophorum species.

Abstract

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 inf4sup+ NO inf3sup- absorption: at nitrogen concentrations below 50 μM, net NH inf4sup+ and NO inf3sup- were absorbed at similar rates, but at higher concentrations, net uptake of NO inf3sup- was significantly faster than that of NH inf4sup+ . The two species also showed similar abilities to assimilate NO inf3sup- . Growth of E. vaginatum under NO inf3sup- nutrition was only slightly less than that under NH inf4sup+ . 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 inf3sup- as a N source supports the view that NO inf3sup- availability may be significant even in wet, acidic, arctic soils.