Phytotoxic selectivity analysis of Eucalyptus tereticornisessential oil against rice, Oryza sativa and its weeds,Echinochloa crus-galli and Cyperus rotundus

Abstract

The present study was undertaken to explore the phytotoxic potential of essential oil (EO) fromEucalyptus tereticornis against two major weeds of rice viz Echinochloa crus-galli and Cyperusrotundus. The effect of essential oil was studied on growth (percentage germination, root length andshoot length development) physiological parameters (chlorophyll content and per cent respiration)under controlled conditions in the laboratory. Studies revealed that E tereticornis essential oil (indifferent concentrations ranging from 25 to 250 g/ml) affected the growth and physiology of all thetest 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 g/ml oil concentration seed germinationand seedling development of test weeds were highly affected as compared to rice. C rotundus wasfound to be the most sensitive weed among test plants. In chlorophyll content the reduction at 250 g/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 g/ml of essential oil was 20, 40 and99 per cent in O sativa, E crus-galli and C rotundus respectively. The present study concludes thatessential oil of E tereticornis shows the toxicity selectively towards the E crus-galli and C rotunduscompared to O sativa