Dudai, N., Aromatic, Medicinal and Spice Crops, ARO, Newe Ya'ar Research Center, P.O. Box 1021, Ramat Yishay 30095, Israel
Chaimovitsh, D., Aromatic, Medicinal and Spice Crops, ARO, Newe Ya'ar Research Center, P.O. Box 1021, Ramat Yishay 30095, Israel
Larkov, O., Aromatic, Medicinal and Spice Crops, ARO, Newe Ya'ar Research Center, P.O. Box 1021, Ramat Yishay 30095, Israel
Fischer, R., Aromatic, Medicinal and Spice Crops, ARO, Newe Ya'ar Research Center, P.O. Box 1021, Ramat Yishay 30095, Israel
Blaicher, Y., Aromatic, Medicinal and Spice Crops, ARO, Newe Ya'ar Research Center, P.O. Box 1021, Ramat Yishay 30095, Israel
Mayer, A.M., Department of Plant and Environmental Sciences, Hebrew University of Jerusalem, Jerusalem 91904, Israel

The allelopathic effect of white micromeria (Micromeria fruticosa) leaves on germinating wheat (Triticum aestivum L.) was examined in sterilized and non-sterilized clay and sandy soils. Seed germination and seedling development were evaluated and the volatile compounds in the soil and in the seeds analyzed. The germination of the seeds and subsequent development of the seedlings were inhibited by addition of the leaves to the soil. The degree of inhibition was found to be concentration dependent, and the extent of inhibition was higher in the sandy soil than the clay. Volatile components from M. fruticosa and their derivatives were found in the soil and in the seeds. Soil sterilization inhibited the degradation of the volatiles but its effect on seedling emergence was not significant. We suggest that the active compounds pulegone and isomenthol are the probable cause of the inhibitory effects. The results demonstrate that leaf residues in soil systems can cause allelopathic effects by releasing volatiles. The compounds are metabolized in the seeds and are able to lead to inhibition of germination. © 2008 Springer Science+Business Media B.V.