Germination response to phytotoxicity of Impatiens parviflora

Biochemical interactions in ecosystems have revealed the ecophysiological significance of secondary metabolites. Biochemical interaction underlies the novel weapons hypothesis thus presenting one of numerous explanations for the spread of invasive species. The knowledge of how invasive species spread in a new environment might be important for their management control. This study was aimed to determine the total phenolics content in Impatiens parviflora (I parv) and evaluate the germination response of monocot and dicot species to phytotoxicity. Wheat and rapeseed germination response to allelopathic activity of worldwide invasive Impatiens species (Balsaminaceae), namely, I. parviflora (native to Central Asia) was assessed ex situ at Aleksandras Stulginskis University in 2016. Phenolic content ranged between 0.32 and 5.53 mg g–1 in aqueous extracts of donor Impatiens. These allelopathic compounds are phytotoxic and usually reduce the growth of neighbouring plants. The data revealed their inhibition of germination and the seedling growth of both recipient species. However, the germination response was different for each recipient species due to different morphology of the seed coat. Inhibition of Impatiens extracts was recorded stronger for rapeseed (R) germination (mean 51.0%) than that for wheat (W) germination (mean 23.8%), possibly due to different seed coat anatomy and, consequently, its permeability. Therefore the strongest inhibition (93.0%) was recorded for rapeseed germination (4.5%) in 0.2% flower and fruit+seed extract of I. parviflora. Parameters of wheat seedlings also exhibited a weaker response to the extract of I. parviflora than that of rapeseed. The data revealed that Impatiens parviflora might negatively affect the regeneration of neighbouring native species in invaded habitats.