Study of the Allelopathic Potential of Extracts of Azadirachta Indica (Neem)

The allelopathic potential of extracts of Azadirachta indica L., which is one of the most dominant weeds in tropical regions of South-west Asia, was investigated under laboratory conditions. The n-hexane-soluble, acetone-soluble and water-soluble fractions obtained from the acetone extract of A. indica shoots inhibited the germination and the growth of roots and shoots of six test plant species. The inhibitory activity of the water-soluble fraction was greatest, followed by that of the n-hexanesoluble and acetone-soluble fractions in all bioassays. Significant reductions in the germination and growth of the roots and hypocotyls were observed as the extract concentration increased. The concentration-dependent responses of the test plants to the fractions suggested that all three fractions might contain allelochemicals, but that the greatest potential was in the water-soluble fraction. These results indicate that A. indica may produce potent allelochemicals, which should be investigated further in the laboratory and the field.