Allelopathic Effects of Essential Oil of Melaleuca bracteata

In our report, the seeds of five weeds（Sorghum-sudangrass hybrid, Lolium perenne L., Trifolium pratense, Pennisetum alopecuroids and Sorghum sudanense） and three crops（Phaseolus radiates L., Raphanus sativus L. and Oryza sativa L.） were used as the research objects. Melaleuca bracteata essential oil, methyleugenol were used as treatment chemicals. The Petri dish method of herbicide indoor bioassay was used to determine the effects of different concentrations of agents on germination and growth indexes of seeds, and the allelopathy of essential oil of M. bracteata on weeds and crop seeds was analyzed. The results indicated that M. bracteate essential oil and methyleugenol inhibit the germination of most weed seeds, and the inhibitory effect of M. bracteate essential oil on P. alopecuroides is the strongest, and the EC50 value is 67.53 μg/mL, while methyl eugenol has the strongest inhibitory effects on S. sudanense, the EC₅₀ value is 94.95 μg/mL. In addition to P. radiatus L. seeds, the two chemicals inhibit the germination potential and germination index of most of seeds. The inhibitory effects of methyl eugenol on the stem length of seeds are stronger than that of the essential oil of M. bracteate. The inhibitory effects of the essential oil of M. bracteate and methyl eugenol on the root length of S. sudanense are the strongest, whose EC₅₀ value is 43.45 μg/mL and 75.05 μg/mL, respectively. The absolute value of allelopathy comprehensive effects of the two chemicals on weed seeds are higher than that of crop seeds on the whole. According to the order from strong to weak, the allelopathy comprehensive effects of the essential oil of M. bracteate on weed seeds are as follows: P. alopecuroides, S. sudanense, L.perenne L., T. pratense and Sorghum-sudangrass hybrid; the allelopathic comprehensive effects of methyleugenol on weed seeds are as follows: S. sudanense, P. alopecuroides, L. perenne L.,Sorghum-sudangrass hybrid and T. pratense. The overall absolute value of the combined effects of the two chemicals on O. sativa L. and R. sativus L. are higher than that of P. radiatus L. However, the comprehensive effects of the two chemicals on P. radiatus L. is not obvious.