Effects of aqueous extractions of Conyza canadensis on germination and seedling growth of four weeds

Effects of aqueous extract from different parts of Conyza canadensis on weeds Digitaria sanguinalis, Echinochloa crusgalli, Abutilon theophrasti and Amaranthus retroflexus were tested in Petri dishes. The results showed that aqueous extract from root, stem, leaf, flower and whole plant had inhibated effect on the seed germination and seedling growth of the 4 tested weeds. The aqueous extract from flower, leaf and stem, especially flower had higher inhibiting on the seed germination and seedling growth of all tested weeds than the extract from root and whole plant. At 100 g·L-1 concentration, the synthetic effect(SE) of the aqueous extract from C. canadensis flower, leaf, stem, root and whole plant were 87.64%, 80.65%, 72.19%, 48.24% and 64.08%, respectively. At 100 g·L-1 concentration, the inhibition of the aqueous extract from C. canadensis leaf on D. sanguinalis, A. retroflexus, A. theophrast and E. crusgalli germination were 100.00%, 100.00%, 75.00% and 16.67%, respectively, which suggested that A. retroflexus, A. theophrast and D. sanguinalis were more sensitive to the extract than E. crusgalli. These results showed the aboveground parts of C. canadensis had strong inhibition effects on weeds.