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The Response of Some Ecologically Distinct Plant Species to Nitrate- and to Ammonium-Nitrogen
A. Gigon and I. H. Rorison
Journal of Ecology
Vol. 60, No. 1 (Mar., 1972), pp. 93-102
Published by: British Ecological Society
Stable URL: http://www.jstor.org/stable/2258043
Page Count: 10
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Five herbaceous species, Deschampsia flexuosa, Nardus stricta, Rumex acetosa, Sesleria albicans and Scabiosa columbaria (including two populations of S. columbaria) were chosen on the basis of their ecological distribution and for their range of relative growth rates. They were grown for 38 days in solution culture whose source of nitrogen was either the nitrate or the ammonium form and whose pH values were maintained at 4.2, 5.8 and 7.2. Their growth response supported the hypothesis that some calcifuge species grow better when nitrogen is available in the NH4-N form, that some calcicoles grow better when it is available in the NO3-N form and that the growth of widely-distributed species shows more tolerance to either form. Both populations of S. columbaria responded as predicted from their field distribution. The Swiss population was more tolerant of NH4-N and had a growth optimum at the intermediate pH 5.8 (NO3-N) while the more strict calcicole population from Lathkilldale, G.B., had its optimum growth at pH 7.2 (NO3-N) and was less tolerant of NH4-N. There was no indication of nitrogen deficiency in adversely affected plants or of lack of nitrate reductase systems in the calcifuge species. There was no apparent antagonism for uptake between nitrate and phosphate ions but there were strong indications of antagonism between ammonium and potassium ions in all species except Deschampsia flexuosa. In D. flexuosa potassium concentrations were approximately the same with either source of nitrogen and its ability to take up potassium in the presence of NH4-N could be one factor explaining its tolerance of acidic soils.
Journal of Ecology © 1972 British Ecological Society