In this research we studied the allelopathic activity of 11wild population plants belong to 8 families including (Proveskia abrotanoides, Chrozophora tinctoria, Euphorbia petiolata, Gypsophila aretioides, Heliotropium europaeum, Leptarhabdus parviflora, Euphorbia aellenii, Halimocnemis mollsissima, Karscheninnikovia ceratoides, Calycanthus floridus and Zygophyllum fabago). The plant species were selected from the North-east of Iran on the base of a preliminary survey and examined for their allelopathic potentials. The assay method was dish pack using lettuce (Lactuca sativa L. var Great lake 366) seed germination. The experimental design was Randomized Complete Block Design (RCBD) with 3 replications. The results indicated that 9 species out of 11 tested plant decline lettuce seedling growth (hypocotyle and radicle) in comparison to control. The strongest inhibitory activity was detected in Proveskia abrotanoides which decreased lettuce hypocoyle and radicle growth significantly (95% and 94% respectively) but Leptarhabdus parviflora promoted radicle growth of lettuce (24%). Proveskia abrotanoides might be useful as a natural herbicide. Therefore, further researches need to be conducted on the detection of main volatile constituents that are responsible for this strong allelopathic activity of the mentioned plant by GC/MS and NMR techniques.

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