Allelopathic effect of the invasive Acacia dealbata Link (Fabaceae) on two native plant species in south-central Chile

Abstract

Plant species that growth close to or under the canopy of Acacia dealbata Link (Fabaceae, subfamily: Mimosoideae) within
its non-native range, survive with difficulty or not at all, especially if they are native. This phenomenon has been attributed
to allelopathy; one of the strategies used by A. dealbata to trigger an invasion process. Native species Quillaja saponaria
Molina (tree) and Helenium aromaticum (Hook.) H.L. Bailey (herb), share A. dealbata’s range in South-central Chile. This
study was performed on the Mediterranean Biobío Region of Chile. We evaluated the effect of leaves, flowers, pods and
seeds of A. dealbata on the germination and early growth of these native species. Biological assays were carried out under
laboratory conditions, based on aqueous extracts and the direct effect of plant material. Leaf litter prevented the germination
of both species and seeds of the invasive species impeded the germination of Q. saponaria. Other plant parts from A.
dealbata also induced reductions of hypocotyl and radicle lengths in the native species, reaching over 50 % in some treatment
values. All plant parts caused radicle necrosis, preventing the formation of root hairs and, consequently, jeopardizing the
survival possibility of the recipient species. The results show that A. dealbata can interfere with the establishment of pioneer
herbaceous species in ecological succession and can also affect trees if they are reached by the invasion front.