Metabolic Profiling of Arabidopsis Thaliana Reveals Herbicide- and Allelochemical-Dependent Alterations Before They Become Apparent in Plant Growth

Isoflavonoids can inhibit the growth of certain plants and are produced by leguminous species such as clover used for cover cropping and weed suppression. Isoflavonoids have, therefore, been suspected of playing a part in chemical weed suppression by legumes. The effects of biochanin A, an isoflavone, and catechin, a phytotoxic flavanol on the growth of Arabidopsis thaliana were studied in a cultivation assay and compared to the effect of the synthetic herbicide glyphosate. A. thaliana was most susceptible to glyphosate (EC50 = 1.9 mg L-1) followed by catechin (EC50 = 85 mg L-1). EC50 could not be determined for biochanin A; a concentration of 900 mg L-1 was needed to produce a small (15 %) but statistically significant decrease in biomass. Metabolic profiling by GC-TOF and multivariate data analysis showed metabolic alterations in A. thaliana at doses insufficient to cause decreased plant growth. For the two phytotoxic compounds over 80 % of the annotated plant metabolites were significantly affected by the dose. Even for biochanin A, 72 % of the metabolites were affected. Furthermore, the accumulation of the flavonoid to which A. thaliana was exposed could be followed, as could the accumulation of shikimic acid due to glyphosate treatment.