Phytotoxic activity of foliar volatiles and essential oils of Calamintha nepeta (L.) Savi

Foliar volatiles and essential oils of Calamintha nepeta (L.) Savi, a Mediterranean plant species belonging to the Labiatae family, were investigated for their phytotoxic activities on seed germination and root growth of crops (Lactuca sativa L. and Raphanus sativus L.) and weed species (Lolium perenne L. and Amaranthus retroflexus L.). Foliar volatiles of C. nepeta (L.) Savi strongly inhibited both germination and root growth of lettuce, and its essential oils, especially at 125, 250 and 500μL/L, inhibited both processes in lettuce, radish and A. retroflexus L. species, while displaying a little effect on L. perenne L. By GC-MS, 28 chemicals were identified: 17 monoterpenes, 8 sesquiterpenes, 1 diterpene and 2 miscellaneous. Pulegone was the main constituent of the C. nepeta (L.) Savi essential oils. The terpenic components of essentials oils were probably responsible for the phytotoxic activities.