Allelopathic effects of Conyza canadesis the germination and growth of wheat, sorghum, cucumber, rape and radish

The allelopathic effects of aqueous extract from Conyza canadesis were tested in Petri dishes in Laboratory and Greenhouse assays. The aqueous extract strongly inhibited the germination, germination speed and seedling growth of sorghum (Sorghum vulgare Pers.), cucumber (Cucumis sativus L.), wheat (Triticum aestivum L.), rape (Brassica campestris L.) and radish (Raphanus sativus L.). Rape and radish were more sensitive than other spp. C. canadesis released the allelochemicals mainly as root exudates. The extract inhibited the hypocotyl and root growth of endosperm-removed wheat and sorghum cultivated in darkness, but the inhibitory effect was drastic in sorghum than in endosperm-removed wheat. The aqueous extract decreased the photosynthesis activity but increased the MDA contents of cucumber and radish. Thus allelopathic effects of C. canadesis affects non-photosynthesis activity and MDA, but may also affect the photosynthesis activity.