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

Authors

  • R. BAXTER,

    1. Departments of 1Environmental Biology and 2 Cell & Structural Biology, University of Manchester, Manchester, M13 9PL, UK
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    • *

      Present address: Institute of Terrestrial Ecology, Bangor Research Unit, University College North Wales, Deiniol Road, Bangor, Gwynedd LL57 2UW, UK and where correspondence should be addressed.

  • M. J. EMES,

    1. Departments of 1Environmental Biology and 2 Cell & Structural Biology, University of Manchester, Manchester, M13 9PL, UK
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  • J. A. LEE

    1. Departments of 1Environmental Biology and 2 Cell & Structural Biology, University of Manchester, Manchester, M13 9PL, UK
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SUMMARY

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.

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