|Ahmed, MA; Zarebanadkouki, M; Meunier, F; Javaux, M; Kaestner, A; Carminati, A: Root type matters: measurement of water uptake by seminal, crown and lateral roots in maize, Journal of Experimental Botany, 69, 1199–1206 (2018) [Link]
The ability of plants to take up water from the soil depends on both the root architecture and the distribution and evolution of the hydraulic conductivities among root types and along root length. Mature maize (Zea mays L.) root system is composed of primary, seminal and crown roots alongside with their respective laterals. Our understanding of root water uptake of maize is largely based on measurements of primary and seminal roots. Crown roots might have different ability to extract water from the soil, but their hydraulic function remains unknown. Aim of this study was to measure the location of water uptake in mature maize and investigate differences between seminal, crown and lateral roots. Neutron radiography and injections of deuterated water were used to visualize the root architecture and water transport in five weeks-old maize root systems. Water was mainly taken up by crown roots. Seminal roots and their laterals, which were the main location of water uptake in younger plants, had a minor contribution to water uptake. In contrast to younger seminal roots, crown roots were able to take up water also from their most distal segments. The greater uptake of crown roots compared to seminals is explained by their higher axial conductivity in the proximal parts and by the fact that they are connected to the shoot above the seminals, which favors the propagation of the xylem tension along the crown roots. The deeper water uptake of crown roots is explained by their shorter and fewer laterals, which decreases the dissipation of water potential along the roots.