Effects of an experimentally applied increase in ammonium on growth and amino‐acid metabolism of Sphagnum cuspidatum Ehrh. ex. Hoffm. from differently polluted areas

Abstract

Sphagnum cuspidatum Ehrh. ex. Hoffm. was removed from a relatively remote moorland site at the Migneint, N. Wales and from Holme Moss, S. Pennines — a site that has been subjected to atmospheric pollution deposition for a period of at least the last 200 yr. When exposed to elevated ammonium (NH4+) concentrations (0·1 and 1·0 mM) under laboratory conditions for a period of 30 d, S. cuspidatum from N. Wales showed a marked reduction in growth, whereas in the S. Pennine population, growth was stimulated above that of the untreated control tissue at both 0·1 and 1·0 mM NH4+. The largest growth stimulation, however, was seen at 0·1 mM. The effects of increased NH4+ in the growth medium on tissue total chlorophyll concentration after 30 d exposure were similar in moss from both study sites. There was a small linear decline in chlorophyll concentration with increasing ammonium concentration. Moss from both sites was exposed to 0·1 mM NH4+ for a period of 20 d. There was a marked difference in the response of the different moss populations as indicated by changes in the concentrations of the individual amino acids; notably a dramatic transient increase in glutamine (three‐fold), arginine (19‐fold), and asparagine (fourfold) in the moss from N. Wales. In contrast, in the S. Pennine moss, changes in tissue amino‐N concentration were very much smaller. Possible mechanisms to account for the intraspecific differences in response of the moss from the two study sites to increased ammonium concentrations are discussed. Copyright © 1992, Wiley Blackwell. All rights reserved