Allelopathy of Conyza canadensis on Seed Germination and Seedling Growth of Three Types of Weed

Ethyl acetate,butanol and water extracts from Conyza canadensis were used to test their allelopathic effects on the seed germination and seedling growth of three types of weed [Echinochloa crusgalli(L.) Beauv,Bidens pilosa L,and Mimosa pudica L].The results showed that ethyl acetate extract could strongly inhibited the seed germination and seedling growth of E.crusgalli and B.pilosa.The inhibition increased with the increasing concentration of extract.High concentration of the ethyl acetate extract could effectively inhibit the seed germination and seedling growth of M.pudica L.When the concentration of ethyl acetate reached 0.5 mg/mL,significant differences of seedlings of the 3 species emerged on their root length,stem length and fresh weight compared with the control.When the concentration of ethyl acetate reached 2.0 mg/mL,the respond indexes of allelopathy(RI) of the root length of E.crusgalli and B.pilosa were both-1.00;while the RI of the stem length was-0.97 and-0.78 respectively.The average germination rate of two seeds was 3.3% and 2.2% respectively.The butanol extract could inhibit the seed germination and seedling growth of three weeds,but its inhibition was weaker than the ethyl acetate extract.High concentration of the aqueous extract could effectively promote seedling growth of three weeds.It could be concluded that herbicidal active substances from C.canadensis were probably existing in extracts of ethyl acetate.