Water Uptake Profiles Research Articles

A Continuous Root Water Uptake Isotope Mixing Model

AbstractThe depth‐wise distribution of root water uptake is typically inferred through linear mixing models that utilize knowledge of stable water isotopes in soil and plants. However, these existing models often represent the water uptake profile in discrete segments, potentially introducing significant uncertainty and bias into results. In this study, we introduced a novel root water uptake mixing model that combines a Bayesian linear mixing framework with a continuous root water uptake pattern, named CrisPy. To evaluate the performance of CrisPy, we conducted virtual and field‐based tests under several types of prior information. CrisPy showed accurate and robust reconstruction of the true root water uptake profile under various prior information settings in the virtual test. By contrast, the discrete mixing model, MixSIAR was greatly influenced by the prior information and deviated from the true profile. The root mean squared error of the uptake proportions from CrisPy ranged from 3.6% to 7.4%, while MixSIAR exhibited values of 6.3%–15.2%. Furthermore, posterior predictive checking indicated that CrisPy effectively reconstructed the mean and standard deviations of plant water isotopic compositions in both virtual and field‐based tests. MixSIAR, however, underestimated the mean and overestimated the standard deviation of these compositions. These findings collectively support the enhanced accuracy, greater robustness, and reduced uncertainty of CrisPy in comparison to MixSIAR. Therefore, CrisPy provides a powerful tool for partitioning plant water sources.

A Sulfonated Covalent Organic Framework for Atmospheric Water Harvesting.

We report a sulfonated covalent organic framework (COF) capable of atmospheric water harvesting in arid conditions. The isothermal water uptake profile of the framework was studied, and the network displayed steep water sorption at low relative humidity (RH) in temperatures of up to 45 °C, reaching a water uptake of 0.12 g g-1 at 10 % RH and even 0.08 g g-1 at just 5 % RH, representing some of the most extreme conditions on the planet. We found that the inclusion of sulfonate moieties shifted uptake in the water isotherm profiles to lower RH compared to non-sulfonated equivalents, demonstrating well the benefits of including these hydrophilic sites for water uptake in hot, arid locations. Repeated uptake and desorption cycles were performed on the material without significant detriment to its adsorption performance, demonstrating the potential of the sulfonated COF for real-world implementation.

Chitosan‐gelatin/hydroxyapatite‐based scaffold associated with mesenchymal stem cells differentiate into osteoblasts improves the surface of the bone lesion in mice C57BL/6J

AbstractExtensive injuries to bone tissue are still considered a significant clinical challenge; therefore, developing new bone tissue engineering (BTE) strategies is still necessary. This work aims to construct and characterize a chitosan‐gelatin/hydroxyapatite‐based (CG/H) scaffold to provide well‐design support for mesenchymal stem cell (MSC) growth and differentiation to osteoblasts. First, the CG/H scaffolds are construct by freeze‐drying. Then, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, x‐ray diffraction, water uptake, and degradation profiles evaluate the material's surface. In addition, the CG/H morphological, biochemical, and MSC adhesion processes and growth behavior are also assess, indicating reasonable adhesion rates to the surface, low material cytotoxicity, and excellent alkaline phosphatase activity compared to control on the cellular framework. Based on these results, we obtain a highly biocompatible scaffold and that can support osteoblast differentiation. Finally, the in vivo studies demonstrate the CG/H scaffold with MSC adhere is capable of differentiating into osteoblasts, and the application of this scaffold is able to significantly enhance the closure of the bone lesion. Therefore, the CG/H scaffold has potential clinical application for bone regeneration.

Influence of Alstonia Angustiloba tree water uptake on slope stability: A case study at the unsaturated slope, Pahang, Malaysia

Although previous research has significantly enhanced our understanding of problematic and unsaturated soil behaviour and interaction with structures, there is still an urgent need to address the difficult scenarios that are met with problematic and unsaturated soils. This study examines the effects of tree water uptake at different depths and distances on the improvement of induced water uptakes caused by transpiration via mature Alstonia Angustiloba tree. This study is performed to examine the tree water uptake profile in a vegetated slope with the existence of mature Alstonia Angustiloba tree at the top and the stability of the slope during various precipitation penetration events by which the data of the tree water uptake produced within this section of the slope is recorded and implemented to evaluate the factor of safety (FOS). Slope stability analysis is further conducted to explore how plant transpiration affects slope stability. The results indicate that higher tree water uptake lead to the greatest increase of FOS of the slope up to 53% (from 2.17 to 4.57). The highest tree water uptake recorded was at the slope station with Alstonia Angustiloba tree with a depth of 0.25 m and a distance of 1.1 m from the tree. The tree water uptake utilized in this study can contribute to a carbon-free and eco-friendly approach which can be implemented globally to prevent slope failures.

Fast and Accurate Estimation of Evapotranspiration for Smart Agriculture

AbstractThe ability to quantify evapotranspiration (ET) is crucial for smart agriculture and sustainable groundwater management. Efficient ET estimation strategies often rely on the vertical‐flow assumption to assimilate data from soil‐moisture sensors. While adequate in some large‐scale applications, this assumption fails when the horizontal component of the local flow velocity is not negligible due to, for example, soil heterogeneity or drip irrigation. We present novel implementations of the ensemble Kalman filter (EnKF) and the maximum likelihood estimation (MLE), which enable us to infer spatially varying ET rates and root water uptake profiles from soil‐moisture measurements. While the standard versions of EnKF and MLE update the predicted soil moisture prior to computing ET, ours treat the ET sink term in Richards' equation as an updatable observable. We test the prediction accuracy and computational efficiency of our methods in a setting representative of drip irrigation. Our strategies accurately estimate the total ET rates and root‐uptake profiles and do so up to two‐orders of magnitude faster than the standard EnKF.

Influence of Cedar Essential Oil on Physical and Biological Properties of Hemostatic, Antibacterial, and Antioxidant Polyvinyl Alcohol/Cedar Oil/Kaolin Composite Hydrogels.

Polyvinyl alcohol (PVA) is a safe and biodegradable polymer. Given the unique physical and chemical properties of PVA, we physically cross-linked PVA with kaolin (K) and cedar essential oil (Ced) using the freeze-thawing approach to fabricate PVA/Ced/K sponge hydrogels as hemostatic, antibacterial, and antioxidant wound healing materials. The physicochemical characteristics of PVA/Ced/K hydrogels, including water swelling profiles and gel fractions, were surveyed. Additionally, the functional groups of hydrogels were explored by Fourier transform infrared spectroscopy (FTIR), while their microstructures were studied using scanning electron microscopy (SEM). Furthermore, the thermal features of the hydrogels were probed by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Evidently, alterations in cedar concentrations resulted in significant variations in size, water uptake profiles, and hydrolytic degradation of the hydrogels. The incorporation of cedar into the PVA/K endowed the hydrogels with significantly improved antibacterial competency against Bacillus cereus (B. cereus) and Escherichia coli (E. coli). Moreover, PVA/Ced/K exhibited high scavenging capacities toward ABTS•+ and DPPH free radicals. Beyond that, PVA/Ced/K hydrogels demonstrated hemocompatibility and fast blood clotting performance in addition to biocompatibility toward fibroblasts. These findings accentuate the prospective implementation of PVA/Ced/K composite hydrogel as a wound dressing.

Response of a grassland species to dry environmental conditions from water stable isotopic monitoring: no evident shift in root water uptake to wetter soil layers

AimsWe aimed at assessing the influence of above- and below-ground environmental conditions over the performance of Centaurea jacea L., a drought-resistant grassland forb species.MethodsTranspiration rate, CO2 assimilation rate, leaf water potential, instantaneous and intrinsic water use efficiency, temperature, relative humidity, vapor pressure deficit and soil water content in one plant and root length density in four plants, all grown in custom-made columns, were monitored daily for 87 days in the lab. The soil water isotopic composition in eleven depths was recorded daily in a non-destructive manner. The isotopic composition of plant transpiration was inferred from gas chamber measurements. Vertical isotopic gradients in the soil column were created by adding labeled water. Daily root water uptake (RWU) profiles were computed using the multi-source mixing model Stable Isotope Analysis in R (Parnell et al. PLoS ONE 5(3):1–5, 2010).ResultsRWU occurred mainly in soil layer 0–15 cm, ranging from 79 to 44%, even when water was more easily available in deeper layers. In wet soil, the transpiration rate was driven mainly by vapor pressure deficit and light intensity. Once soil water content was less than 0.12 cm3 cm− 3, the computed canopy conductance declined, which restricted leaf gas exchange. Leaf water potential dropped steeply to around − 3 MPa after soil water content was below 0.10 cm3 cm− 3.ConclusionOur comprehensive data set contributes to a better understanding of the effects of drought on a grassland species and the limits of its acclimation in dry conditions.

Shallow roots of different crops have greater water uptake rates per unit length than deep roots in well-watered soil

PurposeCommonly, root length distributions are used as a first approximation of root water uptake profiles. In this study we want to test the underlying hypothesis of a constant water uptake rate per unit root length over depth.MethodsRoot water uptake profiles were measured using a novel sensor technology. Root length was measured with MRI and by scanning harvested roots. Experiments were performed with pot-grown barley (Hordeum vulgare), maize (Zea mays), faba bean (Vicia faba), and zucchini (Cucurbita pepo).ResultsFor barley, maize, and faba bean, we found that roots in the top 15 cm had significantly greater water uptake rates per unit length than roots in the bottom 30 cm. For zucchini, the trend was similar but not significant. Therefore, variation of root water uptake rates with depth could be explained only partly (61–71%) by a variation of root length with depth.ConclusionThe common approximation of root water uptake profiles by root length distributions relies on constant water uptake rates per unit root length. This hypothesis does not hold in our study, as we found significantly greater water uptake rates per unit length in shallower than in deeper roots. This trend was consistent among species, despite the partly strong variation in physiological parameters. We suggest that this is caused by a decreasing axial transport conductance with depth. This might result in a general underestimation of water uptake rates in shallow soil layers when they are approximated by the root length distribution.

Hydrazine-Hydrazide-Linked Covalent Organic Frameworks for Water Harvesting.

We report a postsynthetic strategy and its implementation to make covalent organic frameworks (COFs) with irreversible hydrazide linkages. This involved the synthesis of three 2D and 3D hydrazine-linked frameworks and their partial oxidation. The linkage synthesis and functional group transformation—hydrazine and hydrazide—were evidenced by 15N multi-CP-MAS NMR. In addition, the isothermal water uptake profiles of these frameworks were studied, leading to the discovery of one hydrazine-hydrazide-linked COF suitable for water harvesting from air in arid conditions. This COF displayed characteristic S-shaped water sorption profiles, a steep pore-filling step below 18% relative humidity at 25 °C, and a total uptake capacity of 0.45 g g–1. We found that even small changes made on the molecular level can lead to major differences in the water isotherm profiles, therefore pointing to the utility of water sorption analysis as a complementary analytical tool to study linkage transformations.

Lyophilized ophthalmologic patches as novel corneal drug formulations using a semi-solid extrusion 3D printer

3D printing technology is a novel and practical approach for producing unique and complex industrial and medical objects. In the pharmaceutical field, the approval of 3D printed tablets by the US Food and Drug Administration has led to other 3D printed drug formulations and dosage forms being proposed and investigated. Here, we report novel ophthalmologic patches for controlled drug release fabricated using a semi-solid material extrusion-type 3D printer. The patch-shaped objects were 3D printed using hydrogel-based printer inks composed of hypromellose (HPMC), sugar alcohols (mannitol, xylitol), and drugs, then freeze-dried. The viscous properties of the printer inks and patches were dependent on the HPMC and sugar alcohol concentrations. Then, the physical properties, surface structure, water uptake, antimicrobial activity, and drug release profile of lyophilized patches were characterized. Lyophilized ophthalmologic patches with different dosages and patterns were fabricated as models of personalized treatments prepared in hospitals. Then, ophthalmologic patches containing multiple drugs were fabricated using commercially available eye drop formulations. The current study indicates that 3D printing is applicable to producing novel dosage forms because its high flexibility allows the preparation of patient-tailored dosages in a clinical setting.

Estimation of Evapotranspiration Rates and Root Water Uptake Profiles From Soil Moisture Sensor Array Data

AbstractEvapotranspiration is arguably the least quantified component of the hydrologic cycle. We propose two complementary strategies for estimation of evapotranspiration rates and root water uptake profiles from soil‐moisture sensor‐array data. One is our implementation of ensemble Kalman filter (EnKF); it treats the evapotranspiration sink term in the Richards equation, rather than soil moisture, as the observable to update. The other is a maximum likelihood estimator (MLE) applied to the same observable; it is supplemented with the Fisher information matrix to quantify uncertainty in its predictions. We use numerical experiments to demonstrate the accuracy and computational efficiency of these techniques. We found our EnKF implementation to be two orders of magnitude faster than either the standard EnKF or MLE, and our MLE procedure to require an order of magnitude fewer iterations to converge than its counterpart applied to soil moisture. These findings render our methodologies a viable and practical tool for estimation of the root water uptake profiles and evaporation rates, with the MLE technique to be used when the prior knowledge about evapotranspiration at the site is elusive.

Removal of oil spills by novel developed amphiphilic chitosan-g-citronellal schiff base polymer

A novel chitosan grafted citronellal (Ch-Cit) schiff base amphiphilic polymer was developed for the adsorptive removal of oil spills. The chemical structure was verified by FT-IR spectroscopy and 1H NMR spectrometer, while the morphological changes and surface area were investigated by SEM and BET analysis tools. The amphiphilic character of Ch-Cit schiff base was controlled through variation of the grafting percentage (G%) of citronellal from 11 to 61%. Dramatic changes in the ion exchange capacity (IEC), solubility and water uptake profiles were established, while the oil adsorption capacity was founded in direct relation with the G (%) of citronellal. Operational conditions such as oil amount, adsorption time, adsorbent dose and agitation speed were investigated. The developed Ch-Cit schiff base exhibited a higher surface area (115.94 m2/g) compared to neat chitosan (57.78 m2/g). The oil adsorption capacity of the Ch-Cit schiff base was greatly improved by 166% and 120% for light crude and heavy crude oil, respectively. Finally, the adsorption process was optimized using response surface methodology (RSM).The results substantiate that the amphiphilic Ch-Cit schiff base could be efficiently applied as a low-cost oil-adsorbent for the removal of crude oil spills from sea-water surfaces.

Innovative Eco-Friendly Hydrogel Film for Berberine Delivery in Skin Applications.

Hydrogel formulations (masks or patches, without tissue support) represent the new frontier for customizable skin beauty and health. The employment of these materials is becoming popular in wound dressing, to speed up the healing process while protecting the affected area, as well as to provide a moisturizing reservoir, control the inflammatory process and the onset of bacterial development. Most of these hydrogels are acrylic-based at present, not biodegradable and potentially toxic, due to acrylic monomers residues. In this work, we selected a new class of cellulose-derived and biodegradable hydrogel films to incorporate and convey an active compound for dermatological issues. Films were obtained from a combination of different polysaccharides and clays, and berberine hydrochloride, a polyphenolic molecule showing anti-inflammatory, immunomodulatory, antibacterial and antioxidant properties, was chosen and then embedded in the hydrogel films. These innovative hydrogel-based systems were characterized in terms of water uptake profile, in vitro cytocompatibility and skin permeation kinetics by Franz diffusion cell. Berberine permeation fitted well to Korsmeyer–Peppas kinetic model and achieved a release higher than 100 µg/cm2 within 24 h. The latter study, exploiting a reliable skin model membrane, together with the biological assessment, gained insights into the most promising formulation for future investigations.

Chitosan oleate-tripolyphosphate complex-coated calcium alginate bead: Physicochemical aspects of concurrent core-coat formation

This study designed chitosan species-coated calcium alginate beads through concurrent core-coat formation. Chitosan oleate was synthesized by carbodiimide chemistry and characterized by 1H NMR and FTIR techniques. Chitosan or chitosan oleate was coated onto the forming alginate or alginate/tripolyphosphate core using vibratory nozzle extrusion-microencapsulation approach, followed by calcium crosslinking. Chlorpheniramine maleate served as a model water-soluble drug. The molecular characteristics, size, shape, morphology, swelling, erosion, water uptake, drug content and drug release profiles of beads were evaluated. Discrete spherical coated beads were obtained through minimizing successive bead adhesion through an interplay of nozzle vibrational frequency and polymeric solution flow rate. The tripolyphosphate ions in the core possessed higher diffusional kinetics than alginate and were better able to attract chitosan species onto bead surfaces to facilitate alginate-chitosan coacervation. Amphiphilic chitosan oleate formed smaller aggregates than chitosan. It interacted with greater ease with core alginate and tripolyphosphate. The gain in alginate/tripolyphosphate interaction with chitosan oleate at the core-coat interface enhanced bead robustness against swelling and water uptake with drug release consequently dependent on the loss of alginate-drug interaction.

Robust Estimation of Absorbing Root Surface Distributions From Xylem Water Isotope Compositions With an Inverse Plant Hydraulic Model

The vertical distribution of absorbing roots is one of the most influential plant traits determining plant strategy to access below ground resources. Yet little is known of natural variability in root distribution since collecting field data is challenging and labor-intensive. Studying stable water isotope compositions in plants could offer a cost-effective and practical solution to estimate the absorbing root surfaces distribution. However, such an approach requires developing realistic inverse modeling techniques that enable robust estimation of rooting distributions and associated uncertainty from xylem water isotopic composition observations. This study introduces an inverse modeling method that supports the assessment of the root allocation parameter (β) that defines the exponential vertical decay of a plants’ absorbing root surfaces distribution with soil depth. The method requires measurements obtained from xylem and soil water isotope composition, soil water potentials, and sap flow velocities when plants’ xylem water is sampled at a certain height above the rooting point. In a simulation study, we show that the approach can provide unbiased estimates of β and its associated uncertainty due to measuring errors and unmeasured environmental factors that can impact the xylem water isotopic data. We also recommend improving the accuracy and power of β estimation, highlighting the need for considering accurate soil water potential and sap flow monitoring. Finally, we apply the inverse modeling method to xylem water isotope data of lianas and trees collected in French Guiana. Our work shows that the inverse modeling procedure provides a robust analytical and statistical framework to estimate β. The method accounts for potential bias due to extraction errors and unmeasured environmental factors, which improves the viability of using stable water isotope compositions to estimate the distribution of absorbing root surfaces complementary to the assessment of relative root water uptake profiles.

Fabrication of semi-interpenetrated PVA/PAMPS hydrogel as a reusable adsorbent for cationic methylene blue dye: isotherms, kinetics and thermodynamics studies

A reusable adsorbent was developed based on semi-interpenetrated hydrogel made of poly(vinyl alcohol) (PVA) and poly(2-acrylamido-2-methylpropane sulfonic acid) (PAMPS) for the adsorptive removal of cationic methylene blue (MB) dye. The developed PVA/PAMPS adsorbent hydrogel was characterized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analyzer (TGA) and scanning electron microscope (SEM) analysis tools. Consequence of the variation of AMPS concentration on water uptake profile and polymer add-on (%) was explored. In addition, batch adsorption studies were performed to evaluate the aptitude of the developed adsorbent for MB dye removal under several adsorption conditions. The results showed an increase in the add-on (%) value up to 70% with increasing AMPS content up to 5%. Moreover, the MB dye removal was occurred quickly at the initial stage and recorded 60% after only 5 min from the initial contact time, while it recorded a maximum value of 86% at 25 oC. The experimental adsorption data were well-fitted to the Langmuir isotherm model and followed the pseudo-second-order kinetic model. Moreover, the adsorption of MB dye by the adsorbent hydrogel was an endothermic process. Besides, the PVA/PAMPS adsorbent exhibited better reusability with a maximum removal (%) exceeded 70% after five consecutive cycles. The results obtained from this study infer that the PVA/PAMPS adsorbent hydrogel could be effectually used as an appropriate and reusable adsorbent for removing cationic MB dye molecules from wastewater bodies.

Causes and consequences of pronounced variation in the isotope composition of plant xylem water

Abstract. Stable isotopologues of water are widely used to derive relative root water uptake (RWU) profiles and average RWU depth in lignified plants. Uniform isotope composition of plant xylem water (δxyl) along the stem length of woody plants is a central assumption of the isotope tracing approach which has never been properly evaluated. Here we evaluate whether strong variation in δxyl within woody plants exists using empirical field observations from French Guiana, northwestern China, and Germany. In addition, supported by a mechanistic plant hydraulic model, we test hypotheses on how variation in δxyl can develop through the effects of diurnal variation in RWU, sap flux density, diffusion, and various other soil and plant parameters on the δxyl of woody plants. The hydrogen and oxygen isotope composition of plant xylem water shows strong temporal (i.e., sub-daily) and spatial (i.e., along the stem) variation ranging up to 25.2 ‰ and 6.8 ‰ for δ2H and δ18O, respectively, greatly exceeding the measurement error range in all evaluated datasets. Model explorations predict that significant δxyl variation could arise from diurnal RWU fluctuations and vertical soil water heterogeneity. Moreover, significant differences in δxyl emerge between individuals that differ only in sap flux densities or are monitored at different times or heights. This work shows a complex pattern of δxyl transport in the soil–root–xylem system which can be related to the dynamics of RWU by plants. These dynamics complicate the assessment of RWU when using stable water isotopologues but also open new opportunities to study drought responses to environmental drivers. We propose including the monitoring of sap flow and soil matric potential for more robust estimates of average RWU depth and expansion of attainable insights in plant drought strategies and responses.

Evaluating the efficacy of different curcumin polymorphs in transdermal drug delivery

Curcumin exists in three polymorphic forms: one monoclinic form and two orthorhombic forms. This work aims to investigate the efficacy of curcumin polymorphs in transdermal drug delivery by formulating curcumin polymorphs and their incorporation in polymeric films. Monoclinic form, Form 1, was precipitated by liquid antisolvent technique from acetone solutions, whereas orthorhombic form, Form 2, was obtained by vacuum evaporation of solutions of curcumin in a mixed solvent of chloroform and hexane (60:40%v/v). The other orthorhombic form, Form 3, was precipitated from dimethylsulfoxide solutions. All three curcumin polymorphs were incorporated into polymeric films made of low molecular weight hydroxypropyl methyl cellulose (HPMC E5LV) along with different plasticizers, and permeation enhancers. Radical scavenging activity and cytotoxicity of curcumin polymorphs on human melanoma cell lines were evaluated. Water uptake, in-vitro release, and in-vitro permeation studies on HPMC films loaded with curcumin polymorph were carried out. Cytotoxicity studies on human melanoma cells (SK-MEL-28) showed that Form 2 results in the highest cell inhibition. Among all three curcumin polymorphs, the free radical scavenging activity of Form 3 was found to be the highest. HPMC films loaded with Form 3 exhibited higher water uptake and higher curcumin release profiles at pH of 5.5 (95.3% in 20 h) and pH 7.4 (79.8% in 20 h) as well as the highest in-vitro permeation compared to the other two curcumin forms. Overall, orthorhombic curcumin polymorphs (i.e., Form 2 and Form 3) showed a higher propensity for transdermal drug delivery as compared to the monoclinic curcumin (Form 1).

Disentangling temporal and population variability in plant root water uptake from stable isotopic analysis: when rooting depth matters in labeling studies

Abstract. Isotopic labeling techniques have the potential to minimize the uncertainty of plant root water uptake (RWU) profiles estimated using multisource (statistical) modeling by artificially enhancing the soil water isotopic gradient. On the other end of the modeling continuum, physical models can account for hydrodynamic constraints to RWU if simultaneous soil and plant water status data are available. In this study, a population of tall fescue (Festuca arundinacea cv. Soni) was grown in amacro-rhizotron and monitored for a 34 h long period following the oxygen stable isotopic (18O) labeling of deep soil water. Aboveground variables included tiller and leaf water oxygen isotopic compositions (δtiller and δleaf, respectively) as well as leaf water potential (ψleaf), relative humidity, and transpiration rate. Belowground profiles of root length density (RLD), soil water content, and isotopic composition were also sampled. While there were strong correlations between hydraulic variables as well as between isotopic variables, the experimental results underlined the partial disconnect between the temporal dynamics of hydraulic and isotopic variables. In order to dissect the problem, we reproduced both types of observations with a one-dimensional physical model of water flow in the soil–plant domain for 60 different realistic RLD profiles. While simulated ψleaf followed clear temporal variations with small differences across plants, as if they were “onboard the same roller coaster”, simulated δtiller values within the plant population were rather heterogeneous (“swarm-like”) with relatively little temporal variation and a strong sensitivity to rooting depth. Thus, the physical model explained the discrepancy between isotopic and hydraulic observations: the variability captured by δtiller reflected the spatial heterogeneity in the rooting depth in the soil region influenced by the labeling and may not correlate with the temporal dynamics of ψleaf. In other words, ψleaf varied in time with transpiration rate, while δtiller varied across plants with rooting depth. For comparison purposes, a Bayesian statistical model was also used to simulate RWU. While it predicted relatively similar cumulative RWU profiles, the physical model could differentiate the spatial from the temporal dynamics of the isotopic composition. An important difference between the two types of RWU models was the ability of the physical model to simulate the occurrence of hydraulic lift in order to explain concomitant increases in the soil water content and the isotopic composition observed overnight above the soil labeling region.

Investigating the root plasticity response of Centaurea jacea to soil water availability changes from isotopic analysis.

Root water uptake is a key ecohydrological process for which a physically based understanding has been developed in the past decades. However, due to methodological constraints, knowledge gaps remain about the plastic response of whole plant root systems to a rapidly changing environment. We designed a laboratory system for nondestructive monitoring of stable isotopic composition in plant transpiration of a herbaceous species (Centaurea jacea) and of soil water across depths, taking advantage of newly developed in situ methods. Daily root water uptake profiles were obtained using a statistical Bayesian multisource mixing model. Fast shifts in the isotopic composition of both soil and transpiration water could be observed with the setup and translated into dynamic and pronounced shifts of the root water uptake profile, even in well watered conditions. The incorporation of plant physiological and soil physical information into statistical modelling improved the model output. A simple exercise of water balance closure underlined the nonunique relationship between root water uptake profile on the one hand, and water content and root distribution profiles on the other, illustrating the continuous adaption of the plant water uptake as a function of its root hydraulic architecture and soil water availability during the experiment.