Changes in cell wall polysaccharides and hydroxycinnamates in wheat roots by aluminum stress at higher calcium supply

The present study was conducted to investigate the cell-wall polysaccharides and hydroxycinnamates in wheat plants (Triticum aestivum L.) under aluminum (Al) stress at a higher level of calcium (Ca) supply. Seedlings were grown in nutrient solution for 7 d and then subjected to treatment solutions containing Al (0 or 100 mu M) and Ca (0 or 2500 mu M) in a 500 mu M CaCl2 solution at pH 4.5 for 8 d. Calcium treatment (2500 mu M) improved root growth significantly under Al-stress conditions. The contents of pectin and hemicellulose in roots were increased under Al-stress conditions, and this increase was conspicuous in the hemicellulosic fraction. The increase in the hemicellulose was attributed to increases in arabinose, xylose, and glucose in neutral sugars. High Ca treatment decreased these contents in Al-stressed cell walls. Aluminum treatment increased the content of ferulic acid, whereas Ca treatment with Al reduced the content. These results suggest that Al may modify the mechanical properties of cell-wall polysaccharides by enhancing the synthesis of arabinoxylan, beta-glucan, and ferulic acid in the cell wall. High Ca treatment may maintain the normal synthesis of these materials even under Al-stress conditions.