Influence of organic acids exuded by plants on the interaction of copper with the polysaccharidic components of the root mucilages

A model of the soil-root interface defined by a network of Ca-polygalacturonate was employed to draw information about the interactions between copper and the polysaccharidic components of the root mucilages. The absorption kinetics show that the matrix has a high affinity and selectivity towards copper and that two carboxylate groups coordinate one metal ion. The complexing activity of the polysaccharidic matrix towards copper was also investigated in the presence of citric, malic, pyruvic, and -galacturonic acids. The results show that the capacity of the matrix to complex copper is related to the organic acid used, which can be explained on the basis of both the stability constants and concentration of the complexes in solution. The ability of these acids to mobilize copper from the polysaccharidic matrix was also investigated.