Allelopathic potential of Tridax procumbens L. on radish and identification of allelochemicals

The allelopathic effects and potent allelochemicals of the invasive weed Tridax procumbens L. were examined in this study. Methanol extract from whole plant of T. procumbens was fractionated and assayed on germination and growth of radish (Raphanus sativus). The F-1, fraction separated from the ethyl acetate extract was most inhibitory (IC50 = 0.22 mg/mL). This fraction induced physiological changes in radish seedlings, by reducing amounts of chlorophylls (41.06%) and carotenoids (35.44%), but increased activity of malondialdehyde (MDA) (21.28%), a cell-membrane responding mechanism against oxidative stresses. Twenty-six compounds were identified from the F-1 fraction by gas chromatography-mass spectrophotometry (GC-MS), to reveal the presence of 9-principal constituents [guaiacol, benzeneacetic acid, phenol, benzeneacetic acid methyl ester, methyl salicylate, vanillic acid, syringol, vanillic acid methyl ester and benzoic acid]. Phenolics accounted for major quantity (41.15%), followed by fatty acids and their derivatives. We found that T. procumbens had strong allelopathic activity, possess potent plant growth inhibitors, which might play role in the invasiveness of T. procumbens. This plant may be a promising source for weed control in agriculture.