Root type matters: measurement of water uptake by seminal, crown and lateral roots in maize

Mutez Ahmed1
1 Soil Physics, University of Bayreuth

P 3.3 in Rhizosphere interactions: Biogeochemical processes at the root-soil interface

Introduction

The ability of crops to capture water from the soil depends on the root architecture and anatomical root traits that determine their radial and axial hydraulic conductance. These properties are not constant but vary along roots and among different root types and their measurement as well as their effect on the location of water uptake remain an open scientific challenge. The objectives of this study were to measure water uptake by maize roots in soils and estimate differences between seminal, nodal and lateral roots.

Material and Methods

We traced the transport of deuterated water (D2O) in the roots of five weeks-old maize in sandy soil using neutron radiography. The transport of D2O was simulated using a diffusion-convection numerical model, which gave the radial permeability and the water uptake of the different root segments. 

Results

 The root architecture of five weeks-old maize consisted of seminal roots with long laterals and crown (nodal) roots with shorter and fewer laterals. Water was mainly taken up by crown roots and their laterals, while laterals of seminal roots, which were the main location of water uptake in younger plants, stopped to take up water. In contrast to seminal roots, crown roots were able to take up water also from their most distal segments. 

Conclusions

 Although seminal roots have been heavily investigated, they do not present the main location of water uptake of a mature maize root system. The ability of crown roots to take up water from their most distal segments can provide an advantage to extract water from deep soil layers and tolerate drought.