Study of Bioassay the Allelopathical Effect of Neem (Azadirachta indica) n-hexane, Acetone and Water-soluble Extracts on Six Weeds

Abstract

Azadirachta indica, or Neem Tree, is an evergreen tree native to Southeast Asia. All parts of the tree have been usedmedicinally for centuries. The allelopathic potential of extracts of Azadirachta indica L., which is one of the mostdominant weeds in tropical regions of South-west Asia, was investigated under laboratory conditions. The n-hexanesoluble,acetone-soluble and water-soluble fractions obtained from the acetone extract of A. indica shoots inhibited thegermination and the growth of roots and shoots of six test plant species. The inhibitory activity of the water-solublefraction was greatest, followed by that of the n-hexane-soluble and acetone-soluble fractions in all bioassays.Significant reductions in the germination and growth of the roots and hypocotyls were observed as the extractconcentration increased. The concentration-dependent responses of the test plants to the fractions suggested that allthree fractions might contain allelochemicals, but that the greatest potential was in the water-soluble fraction. Theseresults indicate that A. indica may produce potent allelochemicals, which should be investigated further in thelaboratory and the field.