Allelopathic potential impact of <i>Senecio angulatus</i> L.F. on native plants

Urban greening had a significant effect on enhancing the distribution of alien plants, which pose a threat to the native species in new areas. <i>Senecio angulatus</i> L.f. (cape ivy) is one of the naturalized species dominant in urban ecosystems in many regions. This study was conducted to evaluate the allelopathic interference of this alien species on the native plants in these habitats in Iran. The allelopathy impact of aqueous extract of stem, leaf and root of cape ivy was estimated on germination and seedling´s growth of five native plants (<i>Agropyron elongatum</i>, <i>Medicago sativa</i>, <i>Portulaca oleracea</i>, <i>Silybum marianum</i>, and <i>Lactuca sativa</i> as indicator plant). The tested species differed in their susceptibility to allelopathy of cape ivy, in which <i>M. sativa</i>, <i>P. oleracea</i>, and <i>L. sativa</i> were significantly sensitive than other species. The inhibitory effect of aqueous extracts from leaves and stems was stronger than those from belowground parts and it revealed that the presence of higher concentrations of natural substances (phenols, flavonoids and antioxidant activity) gave it its efficiency in inhibiting the early growth of native plant. Our results imply that reducing the allelopathic impact of this species during habitat restoration requires the removal of the aboveground parts, including fallen leaves. Furthermore, the information obtained helps score cape ivy risk and impact assessment in the introduced regions.