Implications of Radial Distribution of Organic Matter in the Rhizosphere to Root Water Uptake.

A large fraction of carbon assimilated by many vascular plants is released to the soil in the form of active exudation of long chain polymers—rhizodeposits. Ample empirical evidence has shown that these rhizodeposits sustain rhizosphere microbial communities, facilitate nutrient cycling, and enhance rhi- zosphere soil moisture status. However, the precise physical mechanism by which these deposits facilitate nutreint and water aquistion by roots is uknown. Here we show that steep concentration gradient of organic molecules around individual roots is responsible for substantial water flow to roots without comensurate moisture gradient. This modeling work is supported by experimental data that relate water retention characteristics of the rhizosphere to exudate concentrations.