Natural variation of maize root hydraulic architecture underlies highly diverse water uptake capacities

Abstract

Plant water uptake is determined by the root system architecture and its hydraulic capacity, which together define the root hydraulic architecture. The current research aims at understanding the water uptake capacities of maize (Zea mays), a model organism and major crop. We explored the genetic variations within a collection of 224 maize inbred Dent lines and successively defined core genotype subsets to access multiple architectural, anatomical, and hydraulic parameters in the primary root (PR) and seminal roots (SR) of hydroponically grown seedlings. We found 9-fold, 3.5-fold and 12.4-fold genotypic differences for root hydraulics (Lpr), PR size, and lateral root (LR) size, respectively, that shaped wide and independent variations of root structure and function. Within genotypes, PR and SR showed similarities in hydraulics and, to a lesser extent, in anatomy. They had comparable aquaporin activity profiles that, however, could not be explained by aquaporin expression levels. Genotypic variations in the size and number of late meta xylem vessels were positively correlated with Lpr. Inverse modeling further revealed dramatic genotypic differences in the xylem conductance profile. Thus, tremendous natural variation of maize root hydraulic architecture underlies a high diversity of water uptake strategies and paves the way to quantitative genetic dissection of its elementary traits.

Root Phenotyping and Root Water Uptake Calculation Using Soil Water Contents Measured in a Winter Wheat Field

“…Another one is the variation in radial root hydraulic conductance between different lines in their response to environmental change. In fact, a recent study found significant genetic variations in radial hydraulic conductivity of 224 maize inbred lines (Rishmawi et al, 2023). The importance of root traits in water uptake has been intensively studied over the past decades (Javaux et al, 2013;Lynch, 2013;Lynch, 2019;Postma et al, 2014), but Fig.…”

“…5 is averages over the two sampling points rather than values at any specific time. While water uptake by roots in different soil layers is dynamic and varies instantly following a change in environment (Maurel et al, 2010;Rishmawi et al, 2023), for phenotyping roots and identifying the difference in root water uptake between different varieties in the field, the proposed method for calculating average root water uptake over two sampling time points is sufficient.…”

“…The underlying mechanisms could be physiological, biophysical, or their combination. Physiologically, it could be due to genetic difference in root hydraulic conductivity of different lines (Rishmawi et al, 2023), which control water flow from root-soil surface to the xylem vessels and its subsequent ascent. Biophysically, different lines might have different rhizosphere which mediates the ability of the rhizosphere to hold water and water movement from distant soil into the rhizosphere (Helliwell et al, 2019;Rabbi et al, 2018;Zhang et al, 2020).…”

“…Biophysically, different lines might have different rhizosphere which mediates the ability of the rhizosphere to hold water and water movement from distant soil into the rhizosphere (Helliwell et al, 2019;Rabbi et al, 2018;Zhang et al, 2020). This work cannot untangle these mechanisms, but reveals that relying on root morphology alone is inadequate to assess root uptake, and biophysical and root hydraulic traits also play a significant role and should be included in breeding and screening drought-tolerance varieties (Hallett et al, 2022;Rishmawi et al, 2023).…”

Root hydraulic properties: An exploration of their variability across scales

“…However, different measurement methods may produce different results, especially when comparing methods that rely on a hydrostatic driving force for water flow against those using an osmotic one (Kim et al, 2018 ). Additionally, empirical studies have shown that root hydraulic properties can strongly vary (up to orders of magnitude) among species (Bramley et al, 2009 ; Pratt et al, 2010 ; Steudle, 2000a ), but also among genotypes of one species (Rishmawi et al, 2023 ) or even among individuals of the same genotype (Steudle, 2000a ). This large variability can be explained, at least partially, by the function of roots as hydraulic rheostats, that is, the dynamic changes that root hydraulic properties undergo during development and in response to environmental stimuli (Maurel et al, 2010 ).…”