Impact of root development, soil texture and length of the root hair zone on root water uptake

Background and Aim Root hairs are considered to be crucial for facilitating root water uptake, but the specific conditions influencing their impact remain unclear. We present a model that explores the efficacy of root hairs as a function of soil properties, root type and tissue maturation. In particular, we investigate how the location of root hairs along the root axis, relative to root development, influences root water uptake. The analysis focuses on spatial distribution instead of individual traits such as hair density and length. Methods Using a hydraulic model based on the finite-difference approach, water flow in single maize roots (lateral, seminal, crown, brace) in two contrasting soil textures (sand and loam) was simulated. Soil water potential, root hair length, and the longitudinal extent of the root hair zone were varied to assess root hair impact on water uptake. Key results (1) Root hairs become increasingly relevant in facilitating root water uptake as soil water potentials decrease. (2) Root hair effectiveness is greater in sand than loam, due to the lower hydraulic conductivity of sand in the dry range. (3) In contrast to loam, all root types increase total root water uptake with increasing rhizosphere conductance in sand drier than - 2300 hPa. Conclusion The positive role of hairs in water uptake depends on the profile of root conductivities along the root axis as long as the soil is more conductive than the root. Additionally, root hair functionality depends on soil hydraulic properties and hence is soil texture specific.