Mst. Rokeya Khatun1,2 and Hisashi Kato-Noguchi1
1 Kagawa University, Department of Applied Biological Science, Faculty of Agriculture, Miki, Kagawa 761-0795, Japan
2 Ehime University, The United Graduate School of Agricultural Sciences, 3-5-7 Tarumi, Matsuyama, Ehime 790-8566, Japan
Khatun, M. R. & Kato-Noguchi, H. (2021). Growth inhibition of six test plants by Stephania japonica (Thunb.) Miers leaf extracts is an indication of allelopathic activity. Bulg. J. Agric. Sci., 27 (6), 1093–1099
For sustainable agriculture, exploiting allelochemicals from different groups of plants to treat noxious weeds is increasing. In this study, we assessed the possible allelopathic activity of aqueous methanol extracts of Stephania japonica leaves at six concentrations on the seedling growth of six test plants. The results showed a significant variation in growth of the test plants when treated with the extracts (p < 0.05). At 0.3 g dry weight (DW) equivalent S. japonica leaf extract per mL, the seedling growth of the test plants were completely inhibited except for the barnyard grass shoots, and the inhibitory activity was plant species and concentration dependent. The seedlings of the dicots were the most sensitive to S. japonica extracts with the amount of extract required for 50% shoot and root growth suppression (I50 value) in the range of 0.003–0.008 g DW equivalent S. japonica extract per mL. In comparison, the I50 values for the monocots were 0.003–0.045 g DW equivalent S. japonica extract per mL. The I50 values show the shoot growth of the cress and lettuce and the root growth of the cress, alfalfa, and timothy were the most sensitive to the S. japonica leaf extracts, while barnyard grass was the least sensitive. These results showed that S. japonica probably has allelopathic activity that suppressed the growth of the test plants, indicating that it could be used as a biological tool to combat weeds. However, further research is required to identify and to isolate the inhibitory substances of S. japonica.