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Abstract
Helianthus tuberosus L. (Jerusalem artichoke), a perennial plant native to North America, is one of the most dangerous invasive species in Europe. The fast spread of the plant may be enhanced by its allelopathic effects, through the release of chemical compounds into the environment. The goal of this work was to determine the allelopathic effect of different plant parts of H. tuberosus and to study the temporal changes of allelopathic factors throughout the vegetation period, based on germination bioassays, chemical analysis of allelochemicals, and greenhouse experiments. Bioassay results demonstrated differences in the effect of H. tuberosus extracts, depending on the concentration, the test species, the plant part used for extraction, and the time of the treatment. From the bioactive compounds salicylic acid, 2-OH-cinnamic acid and 4-OH-benzaldehyde showed characteristic distribution patterns throughout the vegetation period. In the competition experiment, the presence of H. tuberosus exerted a strong negative effect on all tested species, independently of their treatment with activated carbon. Based on our results, we concluded that H. tuberosus can interfere with other species through allelochemical interactions. Moreover, seasonal dynamics of allelochemicals could be more important than suspected in plant competition and is likely to play an important role in the spread of the invasive H. tuberosus into new areas.