Allelopathic plants release secondary compounds into the soil that then suppress the growth of nearby plants. Allelopathy has been shown for the invasive Japanese knotweed (Fallopia japonica) and Bohemian knotweed (F. × bohemica). The aggressive and dominant invaders represent a serious threat to the local plant communities outside their native range. Here, we analysed the phenols in the knotweed rhizomes using nuclear magnetic resonance. We also evaluated the allelopathic potential of methanol extracts of F. japonica and F. × bohemica rhizomes and compared these with the effects of the individual knotweed phenols resveratrol, epicatechin and emodin, and their mixture. Rhizomes of both knotweeds contained similar amounts of epicatechin and emodin, with 24% higher resveratrol in F. × bohemica. Only the F. × bohemica methanol extract inhibited radish (Raphanus sativus) seed germination. After 3 days of treatments with 10% (w/v) extracts of both knotweeds, radish seedlings showed up to 70% shorter roots. In contrast, root growth of seedlings treated with the individual phenols resveratrol, epicatechin and emodin, and their mixture, was inhibited by up to 30%, similar to the 1% knotweed extracts. Biochemical parameters of oxidative stress also increased in the roots of treated seedlings, with high levels of malondialdehyde in particular indicating lipid peroxidation. Total antioxidative capacity was also increased in seedlings exposed to 0.6 mg/mL resveratrol and emodin. This study shows higher allelopathic potential of the knotweed methanol extracts compared to the individual phenols and their mixture.

化感植物将次生化合物释放到土壤中，然后抑制附近植物的生长。对侵入性日本虎杖 ( Fallopia japonica ) 和波西米亚虎杖 ( F. ×  bohemica )已显示化感作用。侵略性和占主导地位的入侵者对其原生范围以外的当地植物群落构成了严重威胁。在这里，我们使用核磁共振分析了虎杖根茎中的酚类物质。我们还评估了F. japonica和F.甲醇提取物的化感作用潜力。× 波西米亚根茎，并将这些与单个虎杖酚白藜芦醇、表儿茶素和大黄素及其混合物的效果进行比较。两种虎杖的根茎含有相似量的表儿茶素和大黄素，F中的白藜芦醇含量高出 24% 。× 波西米亚。只有F。×  bohemica甲醇提取物抑制萝卜（Raphanus sativus) 种子发芽。在用 10% (w/v) 两种虎杖提取物处理 3 天后，萝卜幼苗的根部缩短了 70%。相比之下，用单独的酚类白藜芦醇、表儿茶素和大黄素及其混合物处理的幼苗的根生长被抑制高达 30%，类似于 1% 虎杖提取物。处理过的幼苗根部的氧化应激生化参数也增加，高水平的丙二醛尤其表明脂质过氧化。暴露于 0.6 mg/mL 白藜芦醇和大黄素的幼苗的总抗氧化能力也有所提高。该研究表明虎杖甲醇提取物与单独的酚类及其混合物相比具有更高的化感潜力。