Allelopathic potential of Juglans nigra L. to control the invasive tree-of-heaven (Ailanthus altissima (Mill.) Swingle)

摘要

Tree-of-heaven (Ailanthus altissima (Mill.) Swingle), native to China, is one of the worst invasive tree in Europe due to its large impact on ecosystem functioning and an enormous eradication cost. However, limited information is available about the allelopathy-based inhibitory plant against this tree species. Therefore, effect of 1 % leaf aqueous extracts from black walnut (Juglans nigra L.), common hackberry (Celt's occidentalis L.), false indigo bush (Amorpha fruticosa L.) or Chinese toon (Cedrela sinensis Juss.) on its seed germination and seedling growth were examined. Black walnut extract caused maximum 44 % reduction in its germination, but other 3 species caused only 25-30 % decrease. The extract from black walnut and Chinese toon adversely affected the leaf dry matter of the A. altissima seedlings. However, the black walnut and common hackberry extracts significantly increased their root-to-shoot ratio. Black walnut extract increased the leaf soluble sugars (37 %), but reduce the leaf hydrogen peroxide (-27 %) and leaf chlorophyll a+b contents (-20-25%). Thus, the black walnut extract strongly allelopathically suppressed the tree-of-heaven by reducing the germination and seedlings growth. However, the pure juglone (an allelopathically active black walnut flavonoid) at the same concentration that found in leaf extract markedly suppressed the seed germination (-70 %), decreased the leaf hydrogen peroxide concentration (-50 %) but stimulated the seedling roots growth (25 %). The effects of juglone were lower than black walnut extracts on young tree-of heaven plants and synergy with other components of extract has been suggested.