Abstract:

This study aims to investigate the herbicidal activity of coumarin against the invasive plant Bidens pilosa var. radiata in agricultural and forestry settings. Seed germination tests and pot experiments were carried out to study the inhibitory effects and physiological impacts of coumarin on seed germination and plant growth of B. pilosa var. radiata. The results showed that the inhibitory activity of coumarin on seed germination of B. pilosa var. radiata (IC₅₀=108.16 mg/L) was higher than three common allelochemicals: methyl jasmonate, salicylic acid and pyrocatechuic acid. During the germination process of B. pilosa var. radiata seed, treatment with coumarin (50 and 100 mg/L) induced the accumulation of O₂·^- and H₂O₂ in the seedlings, with a particularly notable accumulation of O₂·^- in the cotyledons and roots of the seedlings. Additionally, coumarin treatments significantly affected the activities of POD and SOD in B. pilosa var. radiata seedlings. The addition of coumarin (100-1000 mg/kg) to the growth substrate had a significant impact on the growth, photosynthesis, and respiration of B. pilosa var. radiata plants; after 15 days of treatment, the dry weight of B. pilosa var. radiata plants decreased by 18.4%-67.6% compared to the control, net photosynthetic rate decreased by 22.1%-40.5%, and dark respiration rate decreased by 20.9%-41.7%. These results indicate that coumarin effectively inhibits seed germination and plant growth of B. pilosa var. radiata by inducing the accumulation of reactive oxygen species and inhibiting photosynthesis and respiration. Therefore, coumarin has the potential to be developed into effective agents for controlling B. pilosa var. radiata.

Key words: coumarin, bioactivity, Bidens pilosa var. radiate, ROS, antioxidases, photosynthesis