3.2. High concentration of ABA hormone and lignin precursors in early developing apples undergoing abscission after cold
Next, we performed UPLC-QTOF-MS analysis with the same samples of fruit along with its pedicel collected from 6-year-old Hongro/M9 apple tree. A total of 443 metabolites were detected and labelled by accurate mass m/z and liquid chromatography retention time (Figure 2a). Twenty-five metabolites were selected and annotated fulfilling criteria of p< .05 and |log2 fold change| > 1 (Figure 2b). The ABA hormone was highly concentrated in the ‘Abscission’ group. Additionally, lignin precursors, such as quinic acid and ferulic acid, were accumulated more in fruit and pedicel tissues of the ‘Abscission’ group. Other metabolites that significantly differed in concentration between the ‘Abscission’ and ‘Normal’ groups included either flavonoids or amino acids which were subsequently related to the oxidative stress responses. These metabolomics data were consistent with the results of DEG analysis.