Abstract: To explore the allelopathic effects of Trifolium repens，and clarify its mechanism and pathway of action on Cynodon dactylon，different parts of Trifolium repens（stem and leaf，root）were used to make up of four concentrations（0，30，60，120 g/L）of their extracts. The indoor bioassay method was used to study the changes in seed germination（germination rate，germination potential，germination index，vitality index）and seedling growth（seedling height，root length，dry and fresh weight）of Cynodon dactylon under different treatments. GC‑MS analysis was conducted on the extracts from different parts to analyze their chemical composition and differences. The results showed that treatment with 30 g/L stem and leaf extract promoted the germination and seedling growth of Cynodon dactylon seeds，while treatment with 120 g/L had an inhibitory effect.Among them，the inhibitory effects on seed germination potential，vitality index，and seedling root length were more significant（p<0.05），with inhibition rates of 85%，81%，and 95%.The root extract treatment also showed a trend of low concentration promotion and high concentration inhibition.The comprehensive effect analysis showed that the allelopathic effect of stem and leaf extract（21.84%）on Cynodon dactylon was stronger than that of root extract（13.92%）.Chemical composition analysis was conducted on the extraction solutions of three parts，revealing a total of six different components.Among them，4‑chlorobutyryl chloride，3，4‑dimethylpyridine，2，4‑dimethylpyridine，and 3‑ethylpyridine were only detected in the leaf extraction solution，while methyl mercaptoacetate and 1，1‑difluoro‑1‑isocyanate were only detected in the stem extraction solution.In conclusion，the release of alkaloids through leaves of Trifolium repens may the main reason that affect the seed germination and growth of Cynodon dactylon.

Key words: Trifolium repens, Cynodon dactylon, Extract, Allelopathy, GC?MS analysis

摘要： 为探究白三叶的化感作用，明确其对狗牙根的作用机制和途径，利用白三叶不同部位（茎叶、根）的浸提液分别设置4个质量浓度（0、30、60、120 g/L）处理，采用室内生物测定法，研究不同处理下狗牙根种子萌发（发芽率、发芽势、发芽指数、活力指数）和幼苗生长（苗高、根长、干质量、鲜质量）的变化，并对茎、叶、根不同部位浸提液开展GC-MS测定，分析其化学成分及差异。结果表明，30 g/L的茎叶浸提液处理对狗牙根种子萌发和幼苗生长具有促进作用，而120 g/L处理下为抑制作用，其中对种子发芽势、活力指数和幼苗根长的抑制作用较显著（P<0.05），抑制率达85%、81%和95%；根浸提液处理亦呈现“低促高抑”的趋势。综合效应分析显示，茎叶浸提液（21.84%）对狗牙根的化感作用强于根浸提液（13.92%）。对茎、叶、根3个部位的浸提液进行化学成分分析，共有差异成分6种，其中4-氯丁酰氯、3，4-二甲基吡啶、2，4-二甲基吡啶和3-乙基吡啶仅在叶浸提液中检出，巯基乙酸甲酯和1，1-二氟-1-异氰酸乙烷仅在茎浸提液中检出。综上，白三叶的叶中生物碱类物质含量较高，可能是影响狗牙根种子萌发和幼苗生长的主要因素之一。

关键词: 白三叶, 狗牙根, 浸提液, 化感作用, GC-MS分析