Allelopathic potential of Trifolium resupinatum and T. alexandrium on seed germination of four weed species

Laboratory studies were conducted to determine the seed germination of Amaranthus retroflexus, Convolvulus arvensis, Secale cereale and Sinapis arvensis as affected by water-and methanol-soluble constituents of Persian and Berseem clovers. Aboveground tissues of the clovers were collected during flowering stage and dried. Three concentrations of aqueous and methanolic extracts were used: full-strength (33.3 g L(-1)), half-strength (16.7 g L(-1)) and quarter-strength (8.3 g L(-1)). The weed seeds were placed in petri dishes contained the legume extract, or distilled water (control). Percent seed germination was taken after a week. In general, seed germination of the weed species declined progressively with increasing concentration of the clover extracts. It was found that wild mustard exhibited the greatest sensitivity to both the legume extracts. Compared with aqueous extract, methanolic extract caused more decline in seed germination of the weeds. In addition, compared to Persian clover, Berseem clover was stronger inhibitor of seed germination. Therefore, the amounts of allelochemicals may be different in these clovers. Field bindweed showed the least sensitivity to both the legume extracts. Therefore, field bindweed had probably more tolerance to the allelochemicals produced by the clover species.