/AnMtgsAbsts2009.54463 Water Distribution at the Root-Soil Interface: Why Is There More Water Next to Roots?.

Monday, November 2, 2009: 3:20 PM
Convention Center, Room 411, Fourth Floor

Andrea Carminati1, Ahmad Moradi1, Doris Vetterlein2, Hans-Joerg Vogel2 and Sascha Oswald1, (1)Hydrogeology Department, Helmholtz Centre for Environmental Res., Leipzig, Germany
(2)Soil Physics Department, Helmholtz Centre for Environmental Res., Halle, Germany
Dynamics of water flow from soil to roots presents still important questions. Which are the properties of the soil near the roots – i.e. the rhizosphere? Several studies showed that the rhizosphere has different properties compared to the bulk soil. However, common models of root water uptake neglect it and assume that soil is homogeneous.
In order to investigate the properties and significance of the rhizosphere, we planted lupins in rectangular containers filled with sandy soil and we used neutron radiography to image the water content distribution for 9 days during a drying period and after irrigation.
We observed that the water content next to the roots was higher than in the bulk soil during all drying period. Immediately after irrigation the picture changed: the rhizosphere remained markedly drier than the bulk soil. During the following days the water content in the rhizosphere increased again exceeding that in the bulk soil.
Such water dynamics are caused by the rhizosphere properties. Mucilage exuded by roots form a hydrogel that has a high water holding capacity but that undergoes structural alteration after drying. Mucilage forms a continuous hydraulic pathway across soil and roots, attenuates water depletion around roots and helps plants to resist drought.