THE EXPANSION OF MAIZE ROOT-CAP MUCILAGE DURING HYDRATION .3. CHANGESIN WATER POTENTIAL AND WATER-CONTENT

Root-cap mucilage from aerial nodal roots of maize has been found to h ave water potential values of -11 MPa or lower when air dried. The val ue approaches 0 MPa within 2 min of hydration in distilled water. In t his time the expanding gel absorbs only about 0.3% of the water conten t of fully expanded mucilage. It is concluded that the root-cap mucila ge per se has almost no capacity to retain water in the rhizosphere. A ny function that it may play in the slowing of root desiccation would be indirect. For example, mucilage might decrease pore size between an d within soil aggregates by pulling the particles together in a cycle of nocturnal efflux of water from the root surface, and diurnal drying during transpiration.