Physical properties of axenic maize root mucilage

Root mucilage was collected from 3–4 day-old axenically-grown maize seedlings (Zea mays L. cv. Freya). The water potential of the hydrated mucilage was measured by thermocouple psychrometry and the rheology at low deformation rates was studied using an oscillating cone and plate rheometer which provides information on both the elastic and viscous components of its behaviour. Water potential decreased as mucilage solute concentration increased, reaching a value of −60kPa at 1.2 mg mL⁻¹. At the lowest oscillation rate, the mucilage had a dynamic viscosity of 145 mPa s and behaved as a weak viscoelastic gel. After filtration to remove suspended root cap cells and other solid plant material, mucilage viscosity was reduced to 5–10 mPa s at low oscillation rates and the behaviour was that of a viscous liquid. The decrease in viscosity which occurs on filtration indicates that the root cap cells form an integral part of the gel system, either by interacting directly with each other or via the polysaccharide. Our observations provide further support for the idea that mucilage plays a major role in maintaining root-soil contact in the rhizosphere. This revised version was published online in June 2006 with corrections to the Cover Date.