Effects of aluminum sorption on calcium-polygalacturonate network used as soil-root interface model

The objective of this study is to determine the influence of aluminum sorption on a calcium-polygalacturonate (Ca-PG) network used as a soil-root interface model. The Ca-PG network is exposed to aluminum solutions at different concentrations (25-800 microM) at pH 3.50. High concentrations lead to a release of calcium (80%) and aluminum becomes the predominant reticulating cation of the polygalacturonic chains. The FTIR spectra show how aluminum sorption induces shifts of the characteristic bands of carbohydrates in the spectral regions of 1700-1400 and 1200-800 cm(-1), which are enhanced by decreasing intensities. This might be induced by a weakening of the metal-PG complex through conformational variations of the structure. Scanning electron micrographs also show a collapse of the fibrillar structure of Ca-PG that is due to aluminum sorption. This structural rearrangement suggests that the soil-root interface could modify its functionality, affecting the transport of metal ions (nutrients) across the interface and consequently through the cell membranes.