Metabolites in normal type indicate their modulation shared between the single (drought and heat) and combined stress
Figure 1. Scheme (A) and picture of the compartmented chambers (B) and the sampling method used for the collection of the maize root exudates (C).
Figure 2 . Compounds detected in the maize root exudate collection solution: total phenols (a), total flavonols (b) total flavonoids (c), aconitic acid (d), alanine (e), glycine (f), threonine (g). Plants have been grown under following conditions: control (T1: 25°C, 80% soil field capacity); drought (T2: 25°C, 30% soil field capacity); heat (T3: 32°C, 80% soil field capacity); combined stress (T4: 32°C 30% soil field capacity). The exudates are collected to the following root type-zone: seminal-apical (■), =, seminal-subapical (■), primary-apical (■), primary-subapical (■). The values are reported as means ± standard errors. Three way ANOVA with Tukey post hoc test: *p =0.01-0.05, ** p=0.01-0.001; ***p <0.001.
Figure 3. Unsupervised hierarchical cluster analysis (Euclidean distance; linkage rule: Ward) carried out from root exudates chemical profiles. Metabolites were obtained by UHPLC-ESI/QTOF-MS untargeted analysis, and their intensities used to build up the fold-change heatmap here provided.
Figure 4. Score plot of Orthogonal projection to latent structures discriminant analysis (OPLS-DA) supervised modelling carried out from untargeted metabolomics profiles of root exudates (correlation R2Y = 0.83), prediction ability Q2Y = 0.48).
Figure 5 . Venn diagram summarizing the metabolites differentially up-exuded (A) and down-exuded (B) that resulted from the volcano analysis.