Allelopathic effects and composition of aqueous extracts from different parts of Cav. on L. and L.

Background: Cav. is a high-risk invasive plant that seriously threatens the development of grasslands in southern China. However, the allelopathic effects on L. and L., which are widely cultivated forages around the world, have not been reported.

Methods: To explore the allelopathic mechanism of , the allelopathic effects of aqueous extracts from different parts of . on and were investigated. The germination rate (GR), germination potential (GP), seedling height, fresh weight, and chlorophyll content of and seedlings were measured to elucidate the allelopathy of on the two forages. Based on the five indicators, synthetical allelopathic effects (SAE) of extracts was also calculated. In addition, the allelopathic components of the extracts in were quantitatively revealed by untargeted metabolomics detection. Furthermore, two key allelopathic substances, 1,4-cyclohexanedicarboxylic acid (CHDA) and trehalose, were selected to explore the inhibitory effect on two notorious weed species in China, such as gramineous L. and broad-leaved L.

Result: (1) The inhibitory effects of aqueous extracts from different parts of on recipient plants were different, the root was the weakest, and the whole plants was the strongest, with the values of synthetical allelopathic effects (SAE) on at the highest concentration being -0.12 and -0.40, respectively. (2) Compared with , was generally more susceptible to the extracts. (3) The differences in the content of CHDA or trehalose might be a reason why extracts from different parts of exhibited different allelopathic effects. (4) The herbicidal activity test of key allelopathic substances found that CHDA has a strong inhibitory effect on the germination of and almost does not affect and . Thus, this discovery not only revealed allelopathic effects and components in different parts of , but provided scientific evidence for weed control based on natural plant extracts in the future.