Abstract

Although allelopathy has been reported in several crop and weed species, it is unclearhow allelochemical levels vary during the growth stages of a weed. Therefore, this study was conducted during 2017 in Suncheon, South Korea to examine how extracts from the seed of Ipomoea hederacea and its above-ground plant parts (AGP) harvested atseven, 20, 40, and 120 days after seeding (DAS) might inhibit plant growth. In addition, the total phenoland flavonoid contents and DPPH radical scavenging activity of the seeds and above-groundplant parts were measured at various growth stages. Although the extractsof seedand AGPharvested at seven, 20, 40, and 120 DAS inhibited cucumber and barley growth, growth inhibition rates at different seedling stages were inconsistent. Growth inhibition of cucumbers plants was much higher when treated with water extracts rather than withethanol extracts, but this was not the case with barley. Barley was more sensitive to both water and ethanol extracts than cucumber. In addition, plant height and root lengths were inhibited at higher rates than germination rates regardless of which extract was used.Both growth and germination inhibition rates of Silybum marianum were higher when treated withethanol extracts than when treated with water extracts. In contrast, the I50 values for the germination rate and root length of Echinochloa oryzoides were similar regardless of whether they had been treated with water or ethanol extracts. Shoot fresh weight of Quamoclit coccinea was significantly inhibited by treatments to soil surface or incorporation of dried AGP harvested at 120 DAS compared to the untreated control. The shoot fresh weight of Q. coccineain response to treatments of soil surface and incorporation applicationsat 400 g/m2 was inhibited by 21 and 11%,respectively, compared to the control. On the other hand, there was no inhibition when foliar applications of water and ethanol extracts at5 and10% concentrations were made to Q. coccinea at the 0.5, 2 and 3-4 leaf stages. The total phenol and flavonoid contents and DPPHradical scavenging activity may not be related to the herbicidal potential in seeds and plants of different growth stages of I. hederacea.