Allelopathic activity of medicinal plants and weeds from Pakistan

The phytotoxicity of 20-medicinal plants and weed species from Pakistan was evaluated. Effects of root exudates and dried leaves of test plant species on Lactuca sativa (lettuce) were examined. The phytotoxicity varied with the mode of release of phytotoxins, whether released by root exudates, volatilization or residues. In Plant box method, the Tagetes minuta showed strongest inhibitory activity followed by Setaria verticillata and Mirabilis jalapa) among the species investigated. In Sandwich method, maximum radical growth inhibition occurred in Pyrus pashia followed by Solanum surattense and Solanum villosum. While in Dish-pack method, maximum radical growth inhibition was in Tagetes minuta followed by Prosopis juliflora and Lantana camara. These results may provide benchmark information for further research on the elucidation of chemicals involved in phytotoxicity and might be helpful to develop new and potent bioactive chemicals from natural products.