ALLELOPATHIC ACTIVITY OF LEAVES, STALKS AND ROOTS OF CYMBOPOGON NARDUS
In this study, leaves, stalks and roots of Cymbopogon nardus were separately evaluated to determine the most active parts that contained the strong growth inhibitory activity. Each aqueous methanol extracts of Cymbopogon nardus were determined their allelopathic activity by using six test plant species; alfalfa (Medicago sativa L.), cress (Lepidum sativum L.), lettuce (Lactuca sativa L.), barnyard grass (Echinochloa crus-galli L.), Italian ryegrass (Lolium moltiflorum Lam.) and jungle rice (Echinochloa colonum (L.) P. Beauv.). Four extract concentrations (0.01, 0.03, 0.1 and 0.3 g dry weight equivalent extract/mL) were used for the bioassay. The results showed that these three extracts have inhibitory activity and the percent inhibition increased concentration dependently. However, the inhibitory activity of leaf and root extracts was more effective than stalk extract at 95% level of significance. Barnyard grass, Italian ryegrass and jungle rice were the most sensitive to the leaf, stalk and root extracts, respectively. The concentrations required for 50% growth inhibition of C. nardus leaf, stalk and root extracts on all test plants were 0.000-0.025, 0.009-0.077 and 0.003- 0.023 g dry weight equivalent extract/mL, respectively. In addition, separation of these extracts through silica gel column indicated that root extract contained the most active fractions with strong growth inhibition. The present results suggest that C. nardus may have allelopathic compounds and the root extracts have the greatest inhibitory activity. Studies are in progress for the isolation and identification of allelopathic compounds in aqueous methanol extracts of C. nardus roots for the development of natural herbicides.