Purity verification of different CW components. A, Uronic acid content in different CW components. Plants were grown on plates containing 0 or 50 μm Al for 24 h, and CW materials were extracted from roots and fractionated into different components (for details, see Fig. 2 and “Materials and Methods”). B, Uronic acid content in the pectin fraction extracted by different methods. C, High-performance anion-exchange pulsed-amperometric detection profile of monosaccharides in the pectin fraction. D, Rha content in the pectin fraction and CW materials. Data are means ± sd (n = 3). * Significant difference at P < 0.05.