Metabolomics profiling reveals the potential metabolites and biological pathways of broad bean (Vicia faba L.) under allelochemical stress of Chenopodium ambrosioides L.

We studied the allelopathy of Chenopodium ambrosioides L. volatile oil and its two monomer components (alpha-terpinene and rho-cymene) on Vicia faba L. using physiological measurements and metabolomics profiling. The results showed that the allelochemicals decreased leaf area, seedling height, main root length, biomass and increased stomatal density, among which, volatile oil caused the greatest changes. Variable accumulation of metabolites, in response to treatment with the volatile oil and the two monomers, were identified by GC-MS analysis. Volatile oil significantly decreased the polyols and sugars (myo-Inositol and maltose) and significantly increased the TCA cycle metabolites such as succinic acid, as well as amino acids (glutamic acid, asparagine, beta-alanine and 3-cyano-L-alanine). The two monomers (a-terpinene and rho-cymene), significantly increased the amino acids (glutamine and 3-cyano-L-alanine and rho-cymene) but decreased the sugar gentibiose. Due to the antagonistic effects among the components, they interfere with photosynthesis, amino acid metabolism and TCA cycle of receptor plants. The 3-cyano-L-alanine, the only differential accumulating metabolite was increased in all three treatments, suggesting that allelochemical stress induced the accumulation of cyanide and other toxic substances in receptor plants, thus inhibiting its growth.