Allelopathic Effects of Invasive Woody Plant Species in Hungary

Allelopathy may play an important role in the invasion success of adventive plant species.The aim of this study was to determine the allelopathic potential of invasive woody plant species occurringin Hungary. Juglone index of fourteen invasive woody plant species in Hungary was determined by themethod of Szabó (1997), comparing the effects of juglone and substance extracted of plant species withunknown allelopathic potential on the germination rate, shoot length and rooth length of white mustard(Sinapis alba L.) used as receiver species. Results have proven a more or less expressed allelopathicpotential in case of all species. The juglone index at higher concentration extracts (5 g dry plant materialextracted with 100 ml distilled water) of almost every studied species approaches to 1 or is above 1, thismeans the effect of the extracts is similar to juglone or surpasses it. In terms of juglone index, theallelopathic potential of false indigo (Amorpha fruticosa L.), tree-of-heaven (Ailanthus altissima (Mill.)Swingle) and hackberry (Celtis occidentalis L.) were the highest. Besides these species the treatment withthe extracts of black walnut (Juglans nigra L.), black cherry (Prunus serotina Ehrh.) and green ash(Fraxinus pennsylvanica MARSH. var. subintegerrima (Vahl) Fern.) reduced extremely significantly thegermination rate, shoot and root length, compared to the control.