A scanning electron microscopy of a calcium-polygalacturonate network in the presence of aluminum: a model to investigate soil-root interface processes

The objective of this study was to investigate the effects of aluminum (Al3+) on a calcium-polygalacturonate (Ca-PG) network used as a soil-root interface model. Calcium-PG networks were exposed to Al3+ solutions at different concentrations (100, 200, 400, and 800 mu M) at pH3.50. In the present study, the scanning electron microscopy technique was used to evaluate morphological variations induced by Al(3+)sorption. Results showed how aluminum (Al) sorption induces conformational changes of the Ca-PG complex. The Ca-PG complex shows a regular structure with a honeycomb-like pattern. Interlacing fibrils form a porous system, which can easily allow sorption and/or passage of nutrients as well as toxic elements. As Al becomes the predominant reticulating ion, the pores decrease in size and lose their regular shape. The scanning electron micrographs have in fact shown that Al sorption damages the Ca-PG complex, leading to its collapse; the Ca-Al-PG networks exhibit an irregular uneven structure.