Mineral nutrition of Arnica montana L. and Arnica chamissonis ssp. foliosa maguire: Differences in the cation acquisition

The cultivation of the calcifuge Arnica montana naturally found on poor soils is important because of its pharmaceutical use. Influences of nutrient availability on the cation acquisition by the two Arnica species Arnica montana (Europe) and Arnica chamissonis (North America) were investigated in hydroponic culture. The contents of the divalent cations calcium and magnesium were higher on a dry matter basis in Arnica montana, while the quantities of the monovalent potassium were higher in Arnica chamissonis. High calcium concentrations in the medium lowered the accumulation of other cations in Arnica montana, but Arnica chamissonis was less affected. Arnica chamissonis was more susceptible to increased phosphate concentrations in the medium than Arnica montana. With 0.6 mM phosphate necrotic spots appeared on leaves of Arnica chamissonis. Arnica montana was not affected by this phosphate concentration, but the same symptoms became visible at higher phosphate levels. In both species, no major effect of the chemical form of the N-source on cation accumulation was observed. According to these results, the two Arnica species differ in the discrimination between the monovalent (K+) and the divalent (Ca++, Mg++) cations. Arnica montana and Arnica chamissonis (two species of the same genus) should be considered as an interesting model system for the investigation of cation acquisition and discrimination.