Comparison of allelopathic effects of some brassica species in two growth stages on germination and growth of sunflower

Members of Brassicaceae have been frequently cited as allelopathic crop. The toxic effect of Brassica spp. may be caused by hydrolysis products of glucosinolates that occur in substantial amounts in the vegetative parts of Brassica spp. This study investigated the allelopathic potential of Brassica napus, B. rapa and B. juncea on the sunflower seed germination and seedling growth. Aqueous extracts of three species from two stages (full flowering and straw) of sampling were separately made with 0 (distilled water), 10, 20, 30 and 40% concentrations. This experiment was conducted in 2 × 3 × 5 factorial arrangement based on completely randomized design with five replications. There was a highly significant difference among different concentrations of extracts and also between two stages of extraction. All aqueous extracts significantly affected sunflower germination, germination rate, seedling root and hypocotyl length, fresh and dry matter weight when compared with distilled water control. The greatest concentration showed a stronger inhibitory effect. Root length was more sensitive to extracts than hypocotyl length.