Mineral ion, nitrogen and organic solute pattern in sedges (Carex spp.) - A contribution to the physiotype concept. I. Field samples

Fifty species of Carex from different Austrian habitats have been investigated to elucidate their physiological plasticity with respect to different ecological conditions. The plants were collected in their natural habitats and divided into five ecological groups according to the respective soils (silicate soil, limestone, serpentine, flysch-sandstone, saline soil). Inorganic ions, organic acids, low molecular weight carbohydrates (sugars and sugar alcohols), amino acids, betaines and total N were measured quantitatively together with selected inorganic soil characteristics. No substantial differences could be found in the solute patterns between saline, dry and wet conditions. In particular, proline, betaines and sugar alcohols - known to act as 'compatible solutes' or 'cytoplasmic osmotica' in several salt- or water-stressed plants - were not accumulated in Carex species growing under conditions of low soil water potential. In addition, physiological data were subjected to cluster analysis. With reference to the chosen parameters, the investigated species could not be assigned to the five ecological groups and showed no considerable physiological plasticity. Thus, the genus represents a homogeneous 'physiotype' showing high K/Ca ratios as well as high contents of mono- and disaccharides and γ-aminobutyric acid. K and sugars are the main osmotic solutes in Carex species. Concerning organic acids, mainly citrate, malate and malonate are involved in balancing excess cation uptake. It is concluded that the ecological success of the genus Carex may be largely attributable to an excellent regulation of the ion uptake processes as well as ion balance within cells.