Gel formation on nodal root surfaces of Zea mays. some observations relevant to understanding its action at the root-soil interface

A gel forms on the surface of nodal roots of corn. We have made observations relevant to parameters of its molecular size, the nature of its interaction with clay, and the actual existence of it under normal root growth. In so doing we have anticipated that it is similar to if not the same as the mucilagenous gel at the root soil interface, and that the knowledge gained would be useful in understanding the processes operating at this interface. We have found that gel is present all along a nodal root surface that had elongated into a tube filled with water saturated sand. This observation emphasizes that gel is present under near natural conditions. We have estimated, using a modification of the light scattering technique, that the exudate has a molecular weight of approximately 9 × 10⁷. According to X-ray patterns of the c-axis of exudate films, it appears as if it is an amorphous material. IR spectra of it revealed that it has a characteristic polysaccharide pattern. Addition of exúdate to NH₄-montmorillonite caused a large increase in the intensity of the first order c-axis X-ray diffraction peak and a very slight increase in the calculated d-spacing. The results were interpreted as consistent with the idea that exudate addition to the clay provided a media for better dispersal of the clay plates, however it was not intercalated into the clay lattice. These observations suggest that the exudate may play an important function on the root-soil interface, however more work needs to be done to understand its action at the root-soil interface.