We determined the chemical composition of the essential oils from flowers, stems and leaves of E. maculatum and their phytotoxicities on germination and seedling growth of Lolium perenne L. and Echinochloa crusgalli (L.) Beauv. A total of 31 compounds (accounting for 95.19 %-98.29 % of the whole oil composition) were identified by GC/MS. The ß-cubebene was most abundant compound in flower (52.89 %), leaf (21.86 %) and stem oils (12.97 %). Other major constituents were : a-caryophyllene (9.02 %) in flower oil, a-calacorene (12.84 %) in stem oil and a-cadinol (12.14 %) in leaf oil. These three oils inhibited the seed germination and seedling growth of L. perenne and E. crusgalli, however, the flower oil was most phytotoxic to both weed species. A principal component analysis indicated that minor and major constituents were mostly hydrocarbonated sesquiterpenes, causing the inhibitory activity of flower oil. More research is needed to characterize the reproducibility of the composition of flower oil of E. maculatum to standardize its phytotoxicity for herbicidal use. Its effects in-vivo on the weed species in pot and field assays should also be explored.
Wang† et al. (Wed,) studied this question.