Phytotoxic potential of essential oil from leaves of eucalyptus tereticornis against rice (orza sativa) and its weeds, echinochloa grus-galli and cyperus rotundus

Abstract

The present study was undertaken to explore the phytotoxic potential of essential oil 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 (percent germination, root length and shoot length development) physiological parameters (chlorophyll content and percent respiration) and biochemical changes in macromolecule content (protein and carbohydrate) under controlled conditions in the laboratory. Studies revealed that Eucalyptus tereticornis essential oil (in different concentrations ranging from 25 to 250 µg/ml) adversely affected the growth and physiology of all the test plants. However the effect was more predominant in weeds compare 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 compare to the rice. C. rotundus was found to be the most sensitive weed among test plants. In chlorophyll content, the percent reduction at 250 µg/ml of essential oil was 60% 80% and 99% 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% in O. sativa, E. crus-galli and C. rotundus, respectively. The effect of essential oil on macromolecules, i.e. carbohydrates and proteins also followed the similar trend. The percent reduction in protein content was approximately 40%, 60% and 80% and percent reduction in carbohydrate content was 25% 60% and 90% in O. sativa, E. crus-galli and C. rotundus, respectively on exposure to 100 µg/ml of essential oil. The present study concludes that essential oil of E. tereticornis shows the toxicity selectively towards the E. crus-galli and C. rotundus compare to O.sativa.