Abstract: Allelopathic effects of different concentrations of water extracts of different above-ground organs of the invasive plant Acacia mearnsii on the seed germination of Callicarpa formosana, Lagerstroemia indica, Patrinia villosa and Corchoropsis tomentosa were studied. The main results were as follows: (1)The allelopathic effects of water extracts from stem, leaf and pod on the seed germination of four native species varied much, leaf>stem>pod according to the intensity of allelopathic effects on Callicarpa formosana, Patrinia villosa and Corchoropsis tomentosa. The allelopathic effect on Lagerstroemia indica was concentration-dependent, i.e. at a low concentration, stem>leaf>pod, while at a high concentration, pod>stem>leaf. (2)The allelopathic effects of water extracts from the same organ also varied, the pod water extract showing a strong inhibition on the seed germination of Callicarpa formosana, Lagerstroemia indica and Patrinia villosa, but no significant effect on that of Corchoropsis tomentosa. (3)At high concentrations of stem water extract, the allelopathic strength on seed germination was Corchoropsis tomentosa>Callicarpa formosana>Lagerstroemia indica>Patrinia villosa. (4)The allelopathic strength on Callicarpa formosana, Patrinia villosa and Corchoropsis tomentosa was enhanced with the increase of the water extract concentration of A.mearnsii. (5) The invasion of A.mearnsii was possibly related to the allelopathy inhibiting on the seed germination of accompanied species and has negative impact on the species diversity of the invaded forests.

Key words: Acacia mearnsii De Willd., allelopathy, seed germination, allelopathic effect