Effects of salinity on growth and patterns of ions and organic solutes in five sedges (Carex spp.) with different ecological demands

The present study examines whether halophilous Carex distans, which is adapted to saline habitats, excludes salt ions under controlled conditions and whether the salt exclusion is also effective in non-halophilous Carex species from oligo- (C. limosa. C. rostrata), meso- (C. pilosa) and eutrophic (C. acutiformis) habitats. For C. limosa and C. rostrata, especially from oligotrophic sites, salt is never an ecological factor; therefore, this comparison is regarded rather as a heuristic model to characterize the solute pattern of genus Carex. The five species were grown in 2 different concentrations of Na-salt (control, 10 mM and 40 mM). Salt-tolerant C. distans exhibited no visible injury symptoms, but non-halophilous species showed reduced growth, especially at 40 mM salt, and less NaCl excluding capacity. In conclusion, in moderate salinity (40 mM) the investigated Carex species showed considerable salt resistance associated with the ability to exclude Na⁺ (esp. C. distans) and to maintain high leaf K⁺ levels. Particularly, proline, betaines and sugar alcohols, known to act as 'compatible solutes', were not synthesized as a response to salinity. Although nonhalophilous Carex species showed less salt exclusion capacity than C. distans, the investigated Carex species generally belong to the 'monocot physiotype', characterized by high K⁺ contents, high exclusion capacity for soil ballast ions such as Na⁺, Ca²⁺ and heavy metals and an effective overall regulation of ion absorption.