Some water-related physical properties of maize root-cap mucilage

Abstract The dry weight (0.1%) and water potential -7 kPa) of root-cap mucilage from 3-d-old axenically grown maize seedlings have been determined. The results suggest strong gelling properties and weak water-holding capacity for the mucilage. Root tips from seedlings grown under low or high water stress were fixed by freeze-substitution. Micrographs showed that in both conditions, mucilage was secreted into the periplasmic space and extruded through the cell wall, though in dry conditions, the mucilage was tightly pressed against the root-cap surface. Histochemical and structural evidence is presented indicating chemical changes in the composition of the mucilage upon extrusion and a sharp increase in its hydration at increasing distance from the secretory cells. The possible functions of the root-cap mucilage in the rhizosphere are examined in light of these findings.