Phytotoxic effects of a dominant weed Ligularia virgaurea on seed germination of Bromus inermis in an alpine meadow community

Abstract

Background and aims - Ligularia virgaurea is an invasive weed species in the alpine meadow community that contains allelopathic compounds, which may affect seed germination of other co-existent species. Material and methods - In a laboratory study, allelopathic effects of root, stem and leaf aqueous extracts of Ligularia virgaurea, were evaluated on seed germination of Bromus inermis, a native grass species. Key results - Results showed that root, stem and leaf extracts of Ligularia virgaurea significantly decreased the germination percentage, relative germination percentage, germination index and weighted germination index of Bromus inermis. First germination time and mean germination time of Bromus inermis were also delayed. The concentration of the extracts had no significant effects on the germination indices. The type of extract (root, stem or leaf), on the contrary, showed the following trend on the mean relative germination percentage: RGP leaf extract treatment > RGP stem extract treatment > RGP root extract treatment. The response index values of root, stem and leaf aqueous extracts differ as follows: RI root extracts > RI stem extracts > RI leaf extracts. Conclusion - Our results demonstrate that aqueous extracts of Ligularia virgaurea have a significant allelopathic inhibition on seed germination of Bromus inermis. The root extracts of Ligularia virgaurea have a greater inhibition effect on seed germination of Bromus inermis, relative to stern and the leaf extracts.