ALLELOPATHIC IMPACT OF LEAF AND ROOT EXTRACTS FROM RYEGRASS HYBRID TYPE AND WHEAT

Secondary metabolites that are phytotoxic to some degree are in essence chemicals from nature which may be exploited for weed management. The objective of this dose-response study was to examine the effects from both roots and above-ground plant parts of wheat and ryegrass hybrid type. Thin Layer chromatography (TLC) was utilised to determine whether phytotoxic effects on lettuce seed germination, radicle and cotyledon development could be traced to a particular allelopathic compound. Activity on TLC plates was spread across different zones which all fluoresced under ultra violet (UV) light. Significant inhibition of lettuce germination was observed at zone 5 for the ethyl acetate extract from fresh, immature wheat leaves, while this extract also produced significant germination stimulation at zones 7 and 8. The concentration-dependent responses of lettuce to the extracts, suggest that fractions might contain allelochemicals, with the greatest potential shown by ethyl acetate. Positive and negative effects of wheat and ryegrass hybrid type extracts on lettuce seedling development were noted. The presence of allelochemicals in leaf and root tissues demonstrated that wheat plants are able to synthesise and may exude phytotoxic allelopathic compounds through its root system that could inhibit the root growth of ryegrass hybrid type.