Ammonium toxicity and nitrate response of axenically grown Dactylorhiza incarnata seedlings

Abstract

SUMMARYThe response to ammonium-and nitrate-nitrogen of seedlings of the calcicole orchid species Dactylorhiza incarnata (L.) Sod was tested in axenic in vitro culture of c. 3-month-old protocorms. A pronounced toxicity of ammonium ions was observed. Seedlings raised from plants of a coastal population (f. dunensis (Druce) Soo) and those from plants of an inland population (f. incarnata) showed a different response to nitrogen form. Although ammonium toxicity was similar for seedlings of hoth sites, those of the coastal population showed a positive response to nitrate ions whereas those of the inland population did not. These differences could not be interpreted unequivocally as population differentiation, .\nnmonium toxicity was reduced in alkaline conditions. Yields increased with increasing pH and reached a maximum at pH 8'0. Calcium concentrations of 1 mM were optimal, but calcium levels did not affect the ammonium response. Seedlings did not respond to potassium concentrations in the range of 0-0-4-0 mM superimposed on a basal level of 0-4 mM. No interaction could be demonstrated between ammonium toxicity and potassium levels. Response to pH and ammonium provides a plausible mechanism for the sensitivity of the species to soil decaicification and decrease in seepage intensity of calcium rich groundwatrer in the field.

Effects of mycorrhizal fungi on in vitro nitrogen response of some Dutch indigenous orchid species

“…itself, presumably through toxicity of ammonium ions (Dijk and Eck 19956). The negative effect of nitrogen in Ceratorhiza symbioses might be due to a change in C/N ratio, enabling a faster degradation by the endophyte of the insoluble carbon sources.…”

Window of opportunity of Liparis loeselii populations during vegetation succession on the Wadden Sea islands

“…However, the ecological mechanism that leads to the decline of L. loeselii populations during acidification is still unknown. Dijk and Eck (1995), while studying another orchid species of partly the same habitat, Dactylorhiza incarnata, suggested that ammonium (NH 4 + ) toxicity was responsible for the decline of that species. Van den Berg et al (2005) reported a similar result for the decline of species sensitive to acidity, such as Antennaria dioica and Succisa pratensis.…”

Fontes de nitrogênio no crescimento <em>in vitro</em> de plântulas de <em>Cattleya loddigesii</em> Lindl. (Orchidaceae)

“…A interação entre cálcio e amônio na produção de massa fresca em plântulas de Dactylorhiza incarnata, cultivadas in vitro e provenientes de sementes, foi pesquisada por Dijk e Eck (1995a de carvão ativado, solidificado com 6 g L -1 de ágar e pH ajustado para 5,7 ± 0,1, antes da autoclavagem a 121ºC e 1,5 atm, por 20 min.…”