Allelopathic potential of stoneworts

We investigated growth inhibitory effects of the stoneworts (Characeae) Chara aspera, C. globularis, C. rudis and C. tomentosa on the target organisms Chlorella vulgaris, Acutodesmus acuminatus (Chlorophyta), Synechococcus elongatus, S. leopoliensis (Cyanobacteria) and Aliivibrio fischeri (Proteobateria). Besides fresh Chara shoots, we tested dichloromethane, n-butanol and methanol extracts from dried algae and condensed ice from the lyophilisation process. The study revealed a high potential of allelochemicals of stoneworts for antibiotic treatments, which could be applied in several application fields. We found minor growth inhibition of eukaryotes, but strong effects on Cyanobacteria and A. fischeri with both life algae and extracts. HPLC-analyses of the extracts revealed neither intra-, nor interspecific differences of the composition, only quantitative differences were observed. Cyanobacteria were strongly affected by polar ice extracts indicating the presence of volatile allelochemicals. Application of allelopathically active extracts caused a strong decline of maximum fluorescence yield, a measure of physiological fitness, within the first few minutes and a partial recovery after 60 to 90 minutes. A comparison of active and non-active ice extracts based on GC-MS screening revealed complex patterns for active ones, however an identification of individual compounds was beyond the scope of this study.