CHARACTERISTICS OF EIGHTEEN ESSENTIAL OILS ON ECHINOCHLOA CRUS- GALLI AND GALIUMAPARINE SEEDLING GROWTH

The phytotoxicity characteristics of plants can be successfully used for weed control. To enrich the variety of plant -derived herbicides, we extracted the essential oils from 18 plant species by steam distillation and assayed their herbicidal effects on barnyard grass (Echinochloa crus-galli) and cleavers (Galium aparine). When the target weeds were treated with the 18 essential oils at 0.3 g mL-1, the herbicidal effect on the target weeds was above 80%. The lavender, lemon, and chamomile essential oils showed the best herbicidal effects. The composition of the essential oils was determined by gas chromatography -mass spectrometry (GC -MS). Menthol acetate, linalool, cinene, glycerol triacetate, and 1 -menthol, all of which are terpenoids, were found in relatively high levels in the essential oils. We tested each of these five compounds individually for their inhibiting effects and found that the order of effectiveness was: menthyl acetate> glycerol triacetate> linalool> l -menthol > cinene. The five compounds were tested in combination, in which case, their herbicidal effects were reduced. When barnyard grass was treated with lemon essential oil, the defense enzyme activities were found to increase first and then to decrease with the time up to 48h. Clorophyll a and b levels decreased with treatment time, whereby total chlorophyll content also decreased. These investigations present the herbicidal activity of lavender, lemon, and chamomile essential oils and the active compounds. These identified active substances in the essential oils and their inhibitory effects provide references for the development of bio-herbicides from essential oils for the control of weeds in agricultural system.