Chemical composition and allelopathic activity of essential oils from Geranium wilfordii Maxim.

Essential oils from fresh roots and leaves of G. wilfordii were analysed by Gas chromatography coupled to mass spectrometry (GC-MS). A total of 43 and 33 compounds were identified from roots and leaves, respectively. Germacrone was the most abundant compound in oils of both root (45.27%) and leaf (20.22%). Besides, cyclohexanone (24.14%) and beta-eudesmol (4.18%) were the main components of root oil, while ledol (18.82%) and beta-elemenone (14.65%) were the major compounds in leaf oil. The allelopathic potential of these oils was tested on seed germination of 9-plants [Brassica campestris L. ssp. chinensis Makino var. communis Tsen et Lee, Brassica rapa pekinensis, Brassica campestris L., Cucumis sativus L., Scrophularia ningpoensis Hemsl., Eruca sativa Mill., Lolium perenne L., Clitoria ternatea L. and Portulaca oleracea L]. The seeds of Brassica campestris were the most susceptible to both oils of root and leaf, with RI values lower than -0.93. Furthermore, root oil led to RI values -0.97 for the root length of B. campestris and -0.88 for the shoot length of Lolium perenne. The seedling growth of B. campestris L. and Clitoria ternatea L. exposed to leaf oil showed RI values of about -1. These results suggested that essential oils of G. wilfordii can be used as plant growth regulators.