Germination and growth inhibitory effects of aqueous extracts of different parts of Bidens pilosa L. var Radiata on some vegetable crops

Bidens pilosa L. var radiata is native to Tropical and Central America and a popular medicinal plant in many regions of the world with many biologically active compounds. Experiments were conducted to characterise the germination and growth inhibitory effects of this plant on three vegetables (lettuce, tomato and carrot). Leaf, stem and root aqueous extracts of B. pilosa at 2,4, 6, 8 and 10 mg/mL were applied to examine their effects on the seed germination and seedling growth of the vegetables under laboratory conditions. All the extracts exhibited significant inhibitory effects on the seed germination of the vegetables in a concentration dependent manner. Extract from the leaf was found to be more potent than the other plant parts by completely inhibiting the seed germination, root and shoot growth of tomato at 10 mg/mL. Nevertheless, the stem and the root extracts at low concentrations (mostly 2 mg/mL) had stimulatory effects on the shoots of lettuce and tomato, but with thin seedlings. This medicinal plant could therefore, be a good candidate for the synthesis of eco-friendly herbicide.