The phytotoxicity of invasive plants (IPS) has been identified as one of the main factors influencing their invasion success. The invasion of IPS can occur to varying degrees in the habitats. Two IPS can invade one habitat. This study aimed to evaluate the mono- and co-phytotoxicity of two Asteraceae IPS Solidago canadensis L. and Bidens pilosa L. with different invasion degrees (including light invasion (relative abundance <50%) and heavy invasion (relative abundance ≥50%)) on the horticultural Asteraceae species Lactuca sativa L., through a hydroponic experiment conducted on 9 cm Petri dishes. Leaf extracts of the two IPS can cause significant mono- and co-phytotoxicity. The mono- and co-phytotoxicity of the two IPS were concentration-dependent. The mono-phytotoxicity of S. canadensis was significantly increased with increasing invasion degree, but the opposite was true for the mono-phytotoxicity of B. pilosa. Leaf extracts of B. pilosa with light invasion caused stronger phytotoxicity than those of S. canadensis with light invasion. There may be an antagonistic effect for the co-phytotoxicity caused by mixed leaf extracts of the two IPS compared with those of either S. canadensis or B. pilosa. The phytotoxicity of the two IPS on the growth performance of neighboring plants may play a more important role in their mono-invasion than in their co-invasion. The phytotoxicity appeared to affect the growth performance of S. canadensis individuals more significantly when the invasion was heavy, while the growth performance of B. pilosa individuals seemed to be more influenced by phytotoxicity when the invasion was light. Consequently, the concentration of leaf extracts of IPS, the invasion degree of IPS, the species identity of IPS, and the species number of IPS modulated the mono- and co-phytotoxicity of the two IPS.

入侵植物（IPS）的植物毒性已被确定为影响其入侵成功的主要因素之一。IPS的入侵可以在栖息地发生不同程度的发生。两个 IPS 可以入侵一个栖息地。本研究旨在评价两种菊科植物一枝黄花和鬼针草不同入侵程度（包括轻入侵（相对丰度<50%）和重入侵（相对丰度≥50%））的单一和联合植物毒性。 ）通过在 9 厘米培养皿上进行的水培实验，对园艺菊科物种Lactuca sativa L. 进行研究。两种 IPS 的叶提取物可引起显着的单一和联合植物毒性。两种 IPS 的单一和联合植物毒性均呈浓度依赖性。随着入侵程度的增加，加拿大小蠹的单药毒性显着增加，而毛白花的单药毒性则相反。轻侵的白花叶提取物比轻侵的加拿大柳叶提取物产生更强的药害作用。两种IPS的混合叶提取物与S. canadensis或B. pilosa的叶提取物相比，可能具有拮抗作用。两种IPS对邻近植物生长性能的植物毒性可能在它们的单一入侵中比在它们的共同入侵中发挥更重要的作用。当入侵较重时，植物毒性似乎对加拿大S. canadensis个体的生长性能影响更显着，而当入侵较轻时，植物毒性似乎对B. pilosa个体的生长性能影响更大。因此，IPS叶提取物的浓度、IPS的入侵程度、IPS的物种特性和IPS的物种数调节了两种IPS的单一和联合植物毒性。