Abstract (eng)
Stoneworts (Characeae) are commonly known for their almost epiphyte free appearance, nevertheless studies dealing with their potential of allelopathic activity are scarce.
In this study four stonewort species, two sampling sites each, were collected between May and July 2014 from different aquatic habitats in Austria and tested. Some shoots of the collected stonewort material were used for experiments with living Chara and the other material was prepared for the extractions with dichloromethane and methanol. For detecting growth-inhibiting effects caused by Chara species on microalgae, two photoautotrophic green algae species and two Cyanobacteria as well as one heterotrophic Proteobacterium were chosen as target organisms. In contrast to Cyanobacteria, the green algae were much more resistant to allelochemicals. Compared to the photoautotrophic organisms, which were mainly affected by polar methanol extracts, the heterotrophic Proteobacterium showed a very variable inhibition pattern. Additionally, this Proteobacterium was inhibited by the non-polar dichloromethane extract, which did not show any inhibition of the photoautotrophic target organisms.
Furthermore the extracts were analysed by means of HPLC (high performance liquid chromatography) and GC-MS-analyses (gas chromatography and mass spectrometry).
Additionally two drying methods, air drying at 30 °C and lyophilisation at -100 °C, were compared. Only small differences between the inhibitory activity of these Chara extracts were observable. HPLC-analyses provided similar results.
Besides that, the condensed ice of the lyophilisation was collected and extracted with dichloromethane and N-butanol to test the allelopathic activity of volatile substances.