Phytotoxicity variation throughout the development of Heracleum sosnowskyi Manden

Abstract

The invasive Heracleum sosnowskyi spread across most Europe countries. The giant forb species supress and outcompete native species in natural and semi-natural plant communities changing local biodiversity and landscape in total. Moreover, the species is specific with phototoxic effects by means of photoactive furanocoumarins injurious for human and animal health. In modern ecology the secondary metabolites are considered as significant regulators-mediators in both a plant and an ecosystem. Therefore the study aimed at (i) evaluation of secondary metabolites content, phytotoxicity, and (ii) its accumulation in different parts of H. sosnowskyi throughout the vegetation. The phytotxicity of both invasive species was evaluated in terms of the total phenols content (TPC). Additionally, the biochemical impact on perennial ryegrass (monocots) and winter rapeseed (dicots) seed germination was assessed in aqueous leachates ex situ. Aqueous extracts of 2-yr old H. sosnowskyi exhibited higher phytotoxicity than 1-yr. old plant extracts. The phytotoxic effects of H. sosnowskyi aqueous extracts on the germination depended extract concentration (0.02-0.2%), plant age (1-year, 2-year), plant parts (shoot: stem, leaf, blossom, seed; root) and growth stage (rosette-ripening). The phytotoxicity of H. sosnowskyi determined extract was most strong at flowering stage due to highest TPC (30.42 mg ml-1). All parts of H. sosnowskyi produced phenolics, which inhibited the acceptor-species seed germination.The results suggested that invasive plant species may acquire spreading advantage in new territories through use of their allelochemicals to inhibit germination. Therefore, it is not only H. sosnowskyi giant size, vigorous uptake of nutrients, and reproduction of high seed yield but also biochemical activity that substantially contributes to the success of this invasive plant. [...]