Seed germination on filtrates from soil sampled beneath trees of Eucalyptus globulus, E. nitens and their F1 hybrid

The effect of filtrates from soil sampled from beneath E. globulus, E. nitens and their F₁ hybrid trees was tested on the laboratory germination and root (radicle) growth of linseed, E. globulus and E. nitens seeds. Two Tasmanian field trials were studied: one where E. globulus, E. nitens and their F₁ hybrids were grown inter-mixed as single-tree family plots; the second where E. globulus and E. nitens were grown in replicated blocks. The trees had been growing on each site for 10 and 15 years respectively. No significant differences were detected between filtrates from soils beneath E. nitens and E. globulus for pH, proportion of seeds germinated and root radicle length in either experiment. There was also no difference between the distilled water controls and filtrates from the soils beneath the standing eucalypt trees. There was thus no evidence to suggest a major difference between any of the genetic treatments tested with this plant-based bioassay, although we cannot dismiss the possibility that concentration of the filtrates may reveal differences in bioactivity.