Abstract: To investigate the potential role of allelopathy in plant
interference and in the successful invasion of alien species Solidago
canadensis, aqueous and ethanolic extracts from rhizomes, stems and leaves of
S. canadensis were prepared and used as treatment solutions to assess their
effects on seed germination and seedling growth in four target species,
mulberry (Morus alba); morning glory (Pharbitis nil), wheat (Triticum aestivum)
and rape (Brassica campestris). Reduction and/or growth in germination and
growth of the target plant species in the presence of both aqueous and
ethanolic extracts at different concentrations indicated that the responses
were species-specific and concentration-dependent. Generally, ethanolic
extracts (especially from leaves) imposed stronger effects on both seed
germination and seedling growth. Extracts with lower concentration at 0.001
g/ml dw could stimulate the seedling growth of rape and morning glory, whereas
extracts at any given concentrations have inhibitory effects on wheat and
mulberry. It is suggested that the aqueous and ethanolic extracts of all the
three parts of S. canadensis have significant allelopathic effects. Although
both inhibition and stimulation occurred in the germination and growth of the
target species, extracts with higher concentrations definitely inhibit seed
germination and seedling growth of all target plants. We suggest that
allelopathy plays a more important role than other mechanisms do in the
out-competition of S. canadensis over other plants, and make it invasive in new
habitats.
