Phytotoxic effects of essential oil from Cymbopogon citratus and its physiological mechanisms on barnyardgrass (Echinochloa crus-galli)

Lemongrass (Cymbopogon citratus) essential oil was identified by GC-MS for their major compound constituents: six compounds representing 92.59% of the total essential oil were identified. The main constituent was citral (76.00%). In a laboratory bioassay, high concentration of essential oil significantly inhibited germination and seedling growth of Echinochloa crus-galli and affecting alpha-amylase activity of seeds. In a glass house bioassay, essential oil at concentrations of 1.25, 2.5, 5 and 10% (v/v) was foliar-applied on E. crus-galli at 28 days after sowing at spray volume of 1000 L ha(-1). Observation of leaf wilt symptoms was noted at 6 h after treatment. Chlorophyll a, b and carotenoid content was decreased with concentrations of essential oil, indicating that essential oil interferes with photosynthetic metabolism. C. citratus essential oil caused an electrolyte leakage indicating membrane disruption and loss of integrity. Treated leaves exhibited an increase in thiobarbituric acid reactive substances (TBARS), suggesting lipid peroxidation. It is to conclude that essential oil is phytotoxic and could be utilized as a natural herbicide for future weed control. (C) 2012 Elsevier B.V. All rights reserved.