Is autotoxicity responsible for inhibition growth of new conspecific seedlings under the canopy of the invasive Acacia dealbata Link?

Abstract

Autotoxicity is a particular form of allelopathy and is suspected to be responsible for regulating intraspecific competition under the Acacia dealbata Link (Fabaceae) canopy. Was established a bioassay with controlled conditions following the natural patterns of plant material accumulation under the A. dealbata canopy to determine the effects of chemical compounds released by leaves, bark, flowers and pods of the invasive species on germination and early growth of conspecific seedlings. Morphological changes caused by A. dealbata plant parts in roots of A. dealbata seedlings grown in natural and controlled conditions were evaluated with scanning electron microscopy. The composition and behavior of the phytotoxicity of litter under the A. dealbata canopy throughout its phenological cycle were studied. The main chemical compounds in the soil under the canopy were identified. Most of the tested plant parts inhibited the germination and early seedling growth, prevented the root hair formation, destroyed the rhizodermis and altered the parenchyma tissue of radicles. The pods caused the greatest autotoxicity in seedlings from both study conditions and dominated the plant material accumulated under the canopy for almost all of the phenological cycle. Soil analysis by GC-MS revealed the abundance of fatty acids and the presence of steroids. These results suggest that A. dealbata can control the growth of new conspecific seedlings under its own canopy, and improves the interspecific competitive performance of its adult plants in its non-native range.