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The present study was undertaken to explore the phytotoxic potential of essential oil (EO) from Eucalyptus tereticornis against two major weeds of rice viz Echinochloa crus-galli and Cyperus rotundus. The effect of essential oil was studied on growth (percentage germination, root length and shoot length development) physiological parameters (chlorophyll content and per cent respiration) under controlled conditions in the laboratory. Studies revealed that E tereticornis essential oil (in different concentrations ranging from 25 to 250 μg/ml) affected the growth and physiology of all the test plants. However the effect was more predominant on weeds compared to the rice seedlings. When the seeds of test plants were exposed to 100 and 250 μg/ml oil concentration seed germination and seedling development of test weeds were highly affected as compared to rice. C rotundus was found to be the most sensitive weed among test plants. In chlorophyll content the reduction at 250 μg/ml of essential oil was 60, 80 and 99 per cent in O sativa, E crus-galli and C rotundus respectively. Similarly reduction in respiratory activity on exposure to 250 μg/ml of essential oil was 20, 40 and 99 per cent in O sativa, E crus-galli and C rotundus respectively. The present study concludes that essential oil of E tereticornis shows the toxicity selectively towards the E crus-galli and C rotundus compared to O sativa.
Essential oil, weeds, rice, toxicity, bio-herbicide
