Effect of Local Soil Hydraulic Conductivity Drop Using a Three‐Dimensional Root Water Uptake Model

Abstract

The coupling of soil and root water fluxes at the plant scale is a particularly challenging task. Numerical three‐dimensional plant‐scale models exist that consider these soil–root interactions. The influence of the hydraulic conductivity drop at the microscopic scale and especially the effect on root water uptake is not yet assessed in such models. In this study, an analytical approach describing the hydraulic conductivity drop from the bulk soil to the soil–root interface for a three‐dimensional plant‐scale model was derived and validated by numerical means. With these tools, quantification of the local hydraulic conductivity drop with time was possible. Furthermore, the effect of the hydraulic conductivity drop on the time occurrence of plant stress was evaluated. Root water uptake was assessed, with and without considering the hydraulic conductivity drop around single roots in a three‐dimensional plant‐scale model in terms of total water uptake at the root collar under different soil and root properties. It was shown that the total root water uptake was strongly affected, especially under conditions where the radial root hydraulic conductivity, which regulates root water uptake, was larger than the soil hydraulic conductivity, which regulates water flow in the soil. These findings were backed up by numerical validation of the model using mesh refinement. Incorporation of the hydraulic conductivity drop around individual roots in a three‐dimensional plant‐scale model can solve problems with greater accuracy for larger grid resolutions, and with smaller computational times, than not considering the hydraulic conductivity drop.

Constitutive Expression of a miR319 Gene Alters Plant Development and Enhances Salt and Drought Tolerance in Transgenic Creeping Bentgrass

“…In many circumstances, a more robust root system with increased root length or root biomass has been considered a positive feature under drought conditions (de Dorlodot et al, 2007;Tardieu, 2012). For example, in fields with deep soil, increased root biomass and length would enable plants to reach deeper soil layers and explore a wider soil area, thus leading to more water and nutrient uptake Schroder et al, 2008;Tardieu, 2012). However, new plant cultivars with enhanced drought tolerance generated in several breeding programs exhibited decreased root biomass (Bolaños and Edmeades, 1993;Bruce et al, 2002;Campos et al, 2004;Tardieu, 2012).…”

Plant Water Uptake in Drying Soils

“…Following the mass conservation principle, the flux density of water (motion speed) increases as it gets closer to the root surface, and, in parallel, its water potential decreases as well as the soil conductivity. The rhizosphere is thus susceptible to a local drop of hydraulic conductivity that is favored by high rates of root water uptake and by soil properties, such as coarse textures, that steepen the relationship between soil conductivity and water potential (Shroeder et al, 2008). Soil hydraulic properties and water potential around each root segment therefore set a maximum uptake rate above which a soil restriction to water flow is likely to occur.…”

Implementing small scale processes at the soil-plant interface – the role of root architectures for calculating root water uptake profiles

“…Schröder et al (2008) has shown, that the local soil hydraulic conductivity drop around the roots becomes important when increasing the size of the bulk soil grid cells. We accounted for this by implementing a microscale radial flow model coupled to the bulk soil water flow.…”