Plant Water-Uptake Effects on Salt Distribution at the Root-Soil Interface.

In recent years, increased salinization of soils, along with the depletion of available water, has become a major threat for agriculture. The rhizosphere plays an important role in connecting processes at the soil-plant- atmosphere interface. A better understanding of these connections and their mutual influences can help in improving crop yield. New technologies provide better tools with which to study root structure and function in non-destructive ways. These techniques also provide a refine resolution regarding processes occurring where the roots meet the soil, e.g., water uptake and salt accumulation. Bell peppers are considered to be sodium excluders, whereas carrots take up sodium. Therefore, we hypothesize that salt accumulation around the roots will create a distinction between them under the same irrigation regime. The initial results from rhizoslides (capillary paper growth system) show the salt concentration gradient is decreasing with distance from the root, compared with the bulk that remained more stable. At the microscopic scale, magnetic resonance imaging (MRI) will be implemented to observe root structures, water content and sodium concentration distributions around single roots. At the macroscopic scale, root systems and solute and water distributions within the root zone of plants grown in lysimeters will be monitored using a combination of electrical resistivity tomography (ERT) and local soil sensors. Data will be used to calibrate a model that is expected to predict root water uptake in saline soils for different climatic conditions and different soil water availabilities. Sensitivity analyses from a simulation study with this detailed model for different soil salinities, irrigation regimes and weather scenarios will be presented.