Sandwich method is a very useful tool for screening of the allelopathic effect of leaf litter leacheate under laboratory conditions. This method is a less time-consuming bioassay method and could be used to screen a large number of samples. To investigate the allelopathic activity of different part of 25 wild plants population belong to 12 families which were collected from Iran, an experiment was conducted as a Randomized Complete Block Design (RCBD) with 3 replications in the faculty of Agriculture, Ferdowsi University of Mashhad during 2009-2010. The assay was a new sandwich method using lettuce (Lactuca sativa L. var Great lake 366) seed germination. The results indicated that 18 species showed inhibitory activity upper than 85 percent and declined lettuce seedling growth significantly (hypocotyle and radicle) in comparison to control. The strongest inhibitory activity were detected in Zhumeria majdae, Lavandula angustifolia, Mentha piperita, Achillea bibersteinii, Perovskia abrotanoides, Crocus sativus, Eugenia armoatica, Halimocnemis mollissima, Atriplex canescens, Ziziphora clinopodioides, Althea officinalis, Lycium depressum, Salvia nemorosa, Satureja hortensis, Mellisa officinalis, Krascheninnikovia ceratoides and Ruta graveolen but Juniperus excelsa leaf significantly increased lettuce seedling growth in comparison to control. In conclusion wild plant populations of our country are a valuable potential sources for allelopathy survey and need more attention for the future research especially finding the allelopathic responsible compounds by GC-MS and NMR techniques for using in organic agriculture.

Keywords