Allelopathic effect of ramie extracts on seeds of four field weeds

To explore the allelopathic effects of different solvent extracts of ramie stems and roots on the seeds of four field weeds, the effects were evaluated of different extract concentrations (0.04, 4.00, and 400 g·L⁻¹) with different solvents (water, ethanol, and petroleum ether) of ramie stems and roots on the seed germination and seedling development of the four weeds. The results provide a theoretical basics for future environment friendly herbicides research and weed control. The results showed that the water, ethanol, and petroleum ether extracts of ramie stems and roots had allelopathic-inhibiting effects on the germination of barnyardgrass seeds but had allelopathic-promoting effects on the germination of Setarria viridis. Additionally, the allelopathic effects differed for the different parts of ramie; the extraction solvent and the concentration of the extraction solution affected the germination of Poa peatensis and Eleusine indica. According to the synthetic effects demonstrated by the allelopathic index, the strongest allelopathic-inhibiting effect on barnyardgrass seeds was found with the 400 g·L⁻¹ ethanol extract of ramie stems. The strongest allelopathic-inhibiting effect on Poa peatensis seeds was found with the 400 g·L⁻¹ ethanol extract of ramie roots; the strongest allelopathic-promoting effect was found with the 0.04 g·L⁻¹ petroleum ether extract of ramie root. The 0.04 g·L⁻¹ petroleum ether extract of ramie root had the strongest allelopathic-promoting effect on Setarria viridis seeds. The strongest allelopathic-inhibiting effect on Eleusine seeds was found for the 0.04 g·L⁻¹ water extract of ramie roots; the strongest allelopathic-promoting effect was obtained with 400 g·L⁻¹ petroleum ether extract of ramie stem. So, the allelopathic effect of ramie is related to the treatment object, the concentration, of the extract and the solvent.