Spiny emex (Emex australis Steinh. Family: Polygonaceae) is an annual weed in wheat crop, which adversely affects the growth and yield. We determined the phytotoxic effects of E. australis on germination and early seedling growth of wheat (Triticum aestivum L.) at 15 and 20°C. E australis infested soil significantly reduced the root/shoot length, dry weight and biomass of wheat seedlings than control. A particular high degree of inhibition occurred with E. australis infested soil at 15°C except for seedling emergence. This adverse effect on wheat seedling growth indicates the presence of some growth-retardatory substances possibly released by the residues into the soil medium. Hence, we prepared aqueous extracts from E. australis root, stem, leaf and seed. The stem extract at 15°C inhibited the seedling emergence (15%), root dry weight (23.96%) and biomass of wheat seedlings (34.86%). Leaf extract at 20°C inhibited the root and shoot length (42.96 and 42.03%, respectively) and shoot dry weight (42.86%) of wheat seedlings. Stem extract was most inhibitory to germination at 15°C, however, the germination of wheat seeds was delayed at 20°C, indicating the presence of water-soluble inhibitory substances. The study concluded that E. australis residual soil and aqueous extracts adversely affected the seed germination and early seedling growth of wheat.
Allelopathy, Emex australis, germination, seedling growth, Triticum aestivum, wheat
