197 research outputs found
Non-invasive water flow imaging in roots at cell resolution - FSPM2023
No full textSlides from FSPM2023 talk March 28th 2023 by Valentin Couvreur
Abstract: A key impediment to studying water-related mechanisms in plants is the inability to non-invasively image water fluxes in cells at high temporal and spatial resolution. Here, we report that Raman microspectroscopy, complemented by hydrodynamic modelling, can achieve this goal - monitoring hydrodynamics within living root tissues at cell- and sub-second-scale resolutions. Raman imaging of water-transporting xylem vessels in Arabidopsis thaliana mutant roots reveals faster xylem water transport in endodermal diffusion barrier mutants. Furthermore, transverse line scans across the root suggest water transported via the root xylem does not re-enter outer root tissues nor the surrounding soil when en-route to shoot tissues if endodermal diffusion barriers are intact, thereby separating ‘two water worlds’. </p
Example of data on Zenodo_Valentin Couvreur
No full textThese data are test examples to understand and know the steps to download the data in Zenodo. They do not constitute valid data for use. We decline any responsibility for the use that will be made of them
De la prophylaxie médicale à la prophylaxie idéologique : le cas André Couvreur
No full textAndré Couvreur est un auteur du XIXe siècle auquel la critique littéraire a jusque-là fait mauvais accueil. Médecin diplômé des hôpitaux de Paris et romancier d’une quinzaine de romans, sa première trilogie, Les Dangers sociaux, semble a priori constituer un espace d’étude idéal pour l’épistémocritique. Témoin d’une époque où la littérature participe de la création d’un biopouvoir efficient, Couvreur prend en effet part à la vaste propagande prophylactique de son temps en combattant la syphilis et l’alcoolisme à travers ses livres. Mais l’étiologie de ces grandes maladies dessine un horizon inattendu et les conclusions scientifiques sont balayées par une idéologie radicale, antisémite et misogyne, que cet article entend mettre au jour.André Couvreur is a nineteenth-century author who has so far been poorly received by critics. He was a doctor with a diploma from Paris hospitals and the novelist of about fifteen novels, his first trilogy, Les Dangers sociaux, seems to be an ideal space for epistemocriticism. As a witness of a time when literature participates in the creation of an efficient biopower, Couvreur indeed took part in the vast prophylactic propaganda of his time by fighting syphilis and alcoholism through his books. But the etiology of these major diseases creates an unexpected horizon: scientific conclusions are swept away by a radical ideology that this article intends to bring to light
Estimation of the hydraulic conductivities of lupine roots by inverse modelling of high-resolution measurements of root water uptake
No full textBackground and Aims Radial and axial hydraulic conductivities are key parameters for proper understanding and modelling of root water uptake. Despite their importance, there is limited experimental information on how the radial and axial hydraulic conductivities vary along roots growing in soil. Here, a new approach was introduced to estimate inversely the profile of hydraulic conductivities along the roots of transpiring plants growing in soil.Methods A three-dimensional model of root water uptake was used to reproduce the measured profile of root water uptake along roots of lupine plant grown in soil. The profile of fluxes was measured using a neutron radiography technique combined with injection of deuterated water as tracer. The aim was to estimate inversely the profiles of the radial and axial hydraulic conductivities along the roots.Key Results The profile of hydraulic conductivities along the taproot and the lateral roots of lupines was calculated using three flexible scenarios. For all scenarios, it was found that the radial hydraulic conductivity increases towards the root tips, while the axial conductivity decreases. Additionally, it was found that in soil with uniform water content: (1) lateral roots were the main location of root water uptake; (2) water uptake by laterals decreased towards the root tips due to the dissipation of water potential along the root; and (3) water uptake by the taproot was higher in the distal segments and was negligible in the proximal parts, which had a low radial conductivity.Conclusions The proposed approach allows the estimation of the root hydraulic properties of plants growing in soil. This information can be used in an advanced model of water uptake to predict the water uptake of different root types or different root architectures under varying soil conditions
Photograph of a bust of the author Tasma
No full textPhotograph of a bust of the author Tasma (Jessie Catherine Couvreur). Pencilled on verso of photo 'Tasma - enlargement of an original lent to H.M. Green? by Mrs Erdos, a neice of Tasma
Hydraulic conductivity of soil-grown lupine and maize unbranched roots and maize root-shoot junctions
No full textImproving or maintaining crop productivity under conditions of long term change of soil water availability and atmosphere demand for water is one the big challenges of this century. It requires a deep understanding of crop water acquisition properties, i.e. root system architecture and root hydraulic properties among other char- acteristics of the soil-plant-atmosphere continuum. A root pressure probe technique was used to measure the root hydraulic conductances of seven-week old maize and lupine plants grown in sandy soil. Unbranched root seg- ments were excised in lateral, seminal, crown and brace roots of maize, and in lateral roots of lupine. Their total hydraulic conductance was quantified under steady-state hydrostatic gradient for progressively shorter seg- ments. Furthermore, the axial conductance of proximal root regions removed at each step of root shortening was measured as well. Analytical solutions of the water flow equations in unbranched roots developed recently and relating root total conductance profiles to axial and radial conductivities were used to retrieve the root radial hydraulic conductivity profile along each root type, and quantify its uncertainty. Interestingly, the optimized root radial conductivities and measured axial conductances displayed significant differences across root types and species. However, the measured root total conductances did not differ significantly. As compared to mea- surements reported in the literature, our axial and radial conductivities concentrate in the lower range of her- baceous species hydraulic properties. In a final experiment, the hydraulic conductances of root junctions to maize stem were observed to highly depend on root type. Surprisingly maize brace root junctions were an order of magnitude more conductive than the other crown and seminal roots, suggesting potential regulation me- chanism for root water uptake location and a potential role of the maize brace roots for water uptake more important than reported in the literature
Parameterization of Root Water Uptake Models Considering Dynamic Root Distributions and Water Uptake Compensation
No full textThe spatiotemporal distribution of root water uptake (RWU) depends on the dynamics of the root distribution and compensatory uptake from wetter regions in the root zone. This work aimed to parameterize three RWU models with different representations of compensation: the Feddes–Jarvis model that uses an empirical function, the Feddes model without compensation, and the Couvreur model that is based on a physical description of water flow in the soil–root system. These models were implemented in HYDRUS-1D, and soil hydraulic parameters were optimized by inverse modeling using soil water content and potential measurements and observations of root distributions of winter wheat (Triticum aestivum L.) in horizontally installed rhizotubes. Soil moisture was equally well predicted by the three models, and the soil hydraulic parameters optimized by the models with compensation were comparable. The obtained RWU parameters of the Feddes–Jarvis model were consistent with data reported in the literature, although the pressure heads h3l and h3h for lower and higher transpirations rates, respectively, could not be uniquely identified. Response surfaces of the objective function showed that the root-related parameters of the Couvreur model could be identified using inverse modeling. Furthermore, these parameters were consistent with combined root architectural and hydraulic observations from the literature. The Feddes–Jarvis and Couvreur models simulated similar root-system-scale stress functions that link total RWU to the effective root zone water potential, suggesting that parameters may be transferable between the two models. Simulated RWU profiles differed due to different water redistribution by the root system, but the measurements were not sufficiently precise to observe this redistributio
Incorporating a root water uptake model based on the hydraulic architecture approach in terrestrial systems simulations
No full textA detailed representation of plant hydraulic traits and stomatal closure in land surface models (LSMs) is a prerequisite for improved predictions of ecosystem drought response. This work presents the integration of a macroscopic root water uptake (RWU) model based on the hydraulic architecture approach in the LSM of the Terrestrial Systems Modeling Platform. The novel RWU approach is based on three parameters derived from first principles that describe the root system equivalent conductance, the compensatory RWU conductance, and the leaf water potential at stomatal closure, which defines the water stress condition for the plants. The developed RWU model intrinsically accounts for changes in the root density as well as for the simulation of the hydraulic lift process. The standard and the new RWU approach are compared by performing point-scale simulations for cropland over a sheltered minirhizotron facility in Selhausen, Germany, and validated against transpiration fluxes estimated from sap flow and soil water content measurements at different depths. Numerical sensitivity experiments are carried out using different soil textures and root distributions in order to evaluate the interplay between soil hydrodynamics and plant characteristics, and the impact of assuming time-constant plant physiological properties. Results show a good agreement between simulated and observed transpiration fluxes for both RWU models, with a more distinct response under water stress conditions and with uncertainty in the soil parameterization prevailing to the differences due to changes in the model formulation. The hydraulic RWU model exhibits also a lower sensitivity to the root distributions when simulating the onset of the water stress period. Finally, an analysis of variability across the soil and root scenarios indicates that differences in soil water content are mainly influenced by the root distribution, while the transpiration flux in both RWU models is additionally determined by the soil characteristics
Emergent properties of plant hydraulic architecture : a modelling study
No full textIn a context of increasing needs for food production and limited availability of freshwater for irrigation, understanding the process of root water uptake (RWU) at the plant scale has become a key issue. The complexity of root system hydraulics as well as the difficulty to measure RWU has made of modelling a valuable tool to investigate this process. However major limitations exist regarding (i) the cost of characterising root segments hydraulic properties, and (ii) the computing time of RWU from that scale. This study demonstrates that simple laws, governing RWU at the plant scale, emerge from water flow equations at the root segment scale. In conditions of uniform soil water potential (SWP), RWU is shown to be distributed proportionally to standard fractions (SUF) along the root system. Under spatially heterogeneous SWP, a compensatory RWU term proportional to a root system conductance parameter (Kcomp) is added, which increases water uptake at locations where SWP is higher. Eventually, another root system conductance parameter (Krs) defines leaf water potential from both plant transpiration rate and sensed SWP, which, itself, is the SUF-weighted-mean SWP. The emergent hydraulic parameters (SUF, Kcomp, and Krs) have a physical meaning and may be estimated or measured directly at the plant scale. They are also shown to be intimately related to the water flow available to plant leaves for transpiration, and may be useful complementary indices to characterise crop strategies against water stress. In addition, the identified emergent properties allow an extreme reduction of RWU computing time, and may even be used accurately in one-dimensional spatial discretisation for densely seeded crops such as wheat.(AGRO - Sciences agronomiques et ingénierie biologique) -- UCL, 201
Non-invasive water flow imaging in plant roots at cellular resolution
No full textA key impediment to studying water-related mechanisms in plants is the inability to noninvasively image water fluxes in cells at high temporal and spatial resolution. Here, we report that Raman microspectroscopy, complemented by hydrodynamic modelling using MECHA (Couvreur et al., 2018; Pascut et al., 2021), can achieve this goal - monitoring hydrodynamics within living root tissues at cell- and sub-second-scale resolutions. Raman imaging of watertransporting xylem vessels in Arabidopsis thaliana mutant roots reveals faster xylem water transport in endodermal diffusion barrier mutants. Furthermore, transverse line scans across the root suggest water transported via the root xylem does not re-enter outer root tissues nor the surrounding soil when en-route to shoot tissues if endodermal diffusion barriers are intact, thereby separating ‘two water worlds
- …
