Physical properties of axenic maize root mucilage

Root mucilage was collected from 3-4 day-old axenically-grown maize seedlin gs (Zea mays L. cv. Freya). The water potential of the hydrated mucilage wa s measured by thermocouple psychrometry and the rheology at low deformation rates was studied using an oscillating cone and plate rheometer which prov ides information on both the elastic and viscous components of its behaviou r. Water potential decreased as mucilage solute concentration increased, re aching 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 vis coelastic gel. After filtration to remove suspended root cap cells and othe r 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 decr ease in viscosity which occurs on filtration indicates that the root cap ce lls form an integral part of the gel system, either by interacting directly with each other or via the polysaccharide. Our observations provide furthe r support for the idea that mucilage plays a major role in maintaining root -soil contact in the rhizosphere.