Temperature is one of the key factors in limiting the distribution of plants and controlling major metabolic processes. A series of simulated reciprocal transplant experiments were performed to investigate the effect of temperature on plant chemical composition. Polygonum minus of different lowland and highland origin were grown under a controlled environment with different temperature regimes to study the effects on secondary metabolites. We applied gas chromatography-mass spectrometry and liquid chromatography time-of-flight mass spectrometry to identify the chemical compounds. A total of 37 volatile organic compounds and 85 flavonoids were detected, with the largest response observed in the compositional changes of aldehydes and terpenes in highland plants under higher temperature treatment. Significantly less anthocyanidin compounds and larger amounts of flavonols were detected under higher temperature treatment. We also studied natural variation in the different plant populations growing under the same environment and identified compounds unique to each population through metabolite fingerprinting. This study shows that the origin of different plant populations influences the effects of temperature on chemical composition.
Understanding metabolite changes and underlying metabolic pathways that may be affected in target plants following essential oils (EOs) exposure is of great importance. In this study, a gas chromatography-mass spectrometry (GC/MS) based metabolomics approach was used to determine the metabolite changes in lettuce (Lactuca sativa L.) shoot and root after exposure to different concentrations of W. trilobata EO. Multivariate analyses of principal component analysis (PCA) and orthogonal partial least-discriminant analysis (OPLS-DA) corroborated that shoot and root of lettuce responded differently to W. trilobata EO. In EO-exposed shoot samples, an increase in the levels of malic acid, glutamine, serine, lactose and α-glucopyranose affected important metabolism pathways such as glycolysis, fructose and mannose metabolism and galactose metabolism. The findings suggest that lettuce may be up-regulating these metabolites to increase tolerance against W. trilobata EO. In EO-exposed root samples, changes in fatty acid biosynthesis, elongation, degradation, phenylalanine, tyrosine and tryptophan metabolism were linked to a decrease in lyxose, palmitic acid, octadecanoic acid, aspartic acid, phenylalanine and myo-inositol. These results indicate that W. trilobata EO could cause alterations in fatty acid compositions and lead to inhibition of roots growth. Together, these findings provide insight into the metabolic responses of lettuce upon W. trilobata EO exposure, as well as potential mechanisms of action of W. trilobata EO as bio-herbicides.