Effects and identification of chemical compounds released from the invasive Acacia dealbata Link

The invasion process of Acacia dealbata is partially mediated by releasing allelochemicals that affect native plants and soil microbes. However, non-volatile chemical compounds responsible for the allelopathic effect remain unknown, even though the allelopathic potential of this species has been studied under Europe conditions. We examined the allelopathic potential of aqueous extracts obtained from different plant materials of A. dealbata: litter from leaf, flowers, pods and seeds and fresh leaves and also litter extract's phytotoxicity evolution on germination and early seedling growth of Lactuca sativa L. Bioassays based on aqueous extracts and direct effect of plant materials showed that radicle length (RL), degree of root necrosis and germination percentage were the variables that gave the best prediction for assessing the inhibitory allelopathic effect. Chemical compounds present in all types of litter significantly reduced the hypocotyl and RL of L. sativa. GC-MS analysis reveals the presence predominantly of resorcinol, maculosin and moretenone in leaves; stigmasterol, d-alpha-tocopherol quinone, and lupanin in pods; and methyl p-anisate, p-anisyl alcohol, stigmasterol and anisal were identified in flowers. The inhibitory effect induced on L. sativa by the different plant parts supports the hypothesis that A. dealbata exerts its allelopathic potential throughout its phenological cycle.