The kinetics of aluminum adsorption and desorption by root cell walls of an aluminum resistant wheat (Triticum aestivum L.) cultivar

In the present study, root cell walls were extracted from an Al-resistant wheat (Triticum aestivum L.) cultivar, Atlas 66 to investigate the effect of cell-wall properties on the kinetics of Al adsorption and desorption. Nearly all the Al adsorbed was desorbed by 2.5 mM CaCl2 at pH 4.5, indicating that most of Al ions were electrically bound to cell wall materials. After the cell walls were treated with 1% pectinase for 30 min to degrade part of pectin, the total amount of Al absorbed was decreased by about 50%, indicating that pectin in the cell walls played an important role in binding Al. When the cell walls were preincubated in 1 and 10 mM malate solution overnight to mimic the organic acid secretion by the roots of wheat, the total amount of Al adsorbed was decreased by 60 and 80%, respectively, suggesting that the malate secreted in response to Al stress not only detoxifies Al by its chelating effect, but also reduce the cell walls' capacity to bind Al.