Root Region Research Articles

Microstructure characterization and tensile properties of CMT-based wire plus arc additive manufactured ER2594

A wall component of super-duplex stainless steel was developed using cold metal transfer (CMT)-based wire + arc additive manufacturing (WAAM) technique with an ER2594 wire. The microstructure of the as-deposited wall was explored using optical microscopy and electron backscattered x-ray diffraction (EBSD) analysis. Ferrite count analysis indicated that the austenite-ferrite phase balance was altered along the as-deposited wall body. The average ferrite count near the as-deposited wall was 24.5%, compared with 32.3% in the root region. Widmanstätten and grain boundary austenite were formed near the wall boundary, and intragranular austenite was observed in the different layers. Secondary austenite in the transition layer was also observed. EBSD analysis revealed the sigma (σ) phase and austeno-ferritic phases across the WAAM wall. The tensile and yield strengths of the samples of the as-developed WAAM wall were almost identical regardless of orientations/tropism.

Secondary metabolites as plant defensive strategy: a large role for small molecules in the near root region.

The roles of plant roots are not merely limited to the provision of mechanical support, nutrients and water, but also include more specific roles, such as the capacity to secrete diverse chemical substances. These metabolites are actively secreted in the near root and play specific and significant functions in plant defense and communication. In this review, we detail the various preventive roles of these powerful substances in the rhizosphere with a perspective as to how plants recruit microbes as a preventive measure against other pathogenic microbes, also, briefly about how the rhizosphere can repel insect pests, and how these chemical substances alter microbial dynamics and enhance symbiotic relationships. We also highlight the need for more research in this area to detail the mode of action and quantification of these compounds in the environment and their roles in some important biological processes in microorganisms and plants.

Failure analysis of a secondary driving helical gear in transmission of electric vehicle

The failure cause of a secondary driving helical gear in transmission system of electric vehicle (VE) was analyzed in this paper. The macroscopic fractography, microscopic metallographic observation, hardening depth and hardness and chemical composition inspection, non-metallic inclusions analysis were carried out to evaluate the gear failure mechanism. The stress distributions of the tooth flank using static and dynamic contact finite element simulation were obtained based on ANSYS Workbench software. The results showed that the fracture surfaces of the failed gear originate from the tooth root and exhibit the intergranular brittle fracture, the main reason was low Ti content of the material, hardening depth and hardness in the root region and a number of large carbides on the on the matrix of martensite due to improper heat treatment, also FE simulation results revealed that the high contact stress in the root position and high impact load at the initial stage of gears meshing during the reducer in service possibly led to the fatigue failure.

The Use of Bulk-Fill Flow in the Customization of Glass Fiber Post.

Objectives The aim of this study is to evaluate the influence of different composite resin in the customization of glass fiber posts (GFPs) on bond strength and failure mode. Materials and Methods Thirty bovine roots were selected. The wall roots were reduced so that each wall had a minimum dentin thickness of 1 mm. Thirty GFPs were divided into three groups ( n = 10), which received different types of customization. The first had the GFP relined by bulk-fill flowable composite resin (BF), the second group had the GFP customized by conventional regular composite resin (CR), and the third group was cemented with dual resin cements (DRC), without relining. The root were sectioned, resulting in two 1.0-mm thick slices from cervical root regions only and push-out bond strength test was performed (EMIC, Universal testing machine). To determine failure mode, a stereomicroscope was used at ×40 magnification, with a 2.5D analysis. Statistical Analysis Data were analyzed using two-way ANOVA ( α = 0.05) and Tukey’s test. Results BF (9.08 ± 1.9) and CR (9.17 ± 3.00) did not show a statistically significant difference ( p = 0.961), regarding the bond strength test values. However, there was a statistically significant difference between DRC (5.44 ± 1.89) and the others ( p < 0.05). BF (66.66%) and the CR group (47.61%) presented a predominantly failure mode type 6: mixed between resin cement and composite. While the highest failure index of the DRC group was type 2: adhesive between resin cement and dentin (47.61%). Conclusion BF can be an alternative for the customization of fiber posts, since it presented a similar behavior to the established technique with conventional composites.

Scanning electron microscopic evaluation of the efficacy of 5% ethylenediaminetetraacetic acid for smear layer removal.

The purpose of the study was to evaluate the smear layer removal efficacy of novel Saver® irrigating solution including 5% EDTA and to compare the 17% EDTA as the most used counterpart. Forty-four single-rooted teeth were divided into four groups, were instrumented, and irrigated. The smear treatment groups were as follows: sterile distilled water; 5.25% sodium hypochlorite; Saver®; 17% EDTA. The root samples were blinded. The micrographic images of root samples were collected by scanning electron microscope. The percentages of open dentin tubules were quantified using an image analysis software on micrographs. Two-way ANOVA followed by Tukey's multiple comparisons was used (p < .05). The 17% EDTA showed the highest percentages of open dentin tubules than the other treatments (p < .01). The mean percentages of open dentin tubules of 17% EDTA revealed statistically highly significant differences than Saver® treatment in all root regions (p < .01). Dentin tubules were covered by dense smear layer in distilled water irrigation whereas, the tubular pattern of dentin structure was not observed in hypochlorite irrigation. The commercial Saver® product presented to be less cleaning property on the smear layer than 17% EDTA and failed to show any improvement in the removal of smear layer compared with its tested counterpart.

Surface Submillimeter Papillae Enhanced Mechanical Property of Membrane

AbstractThe surface topographies of natural surfaces play significant roles for improving the ability to adapt to the environment. The micropapilla of lotus leaf is always used to enhance its self‐cleaning performance. However, the function of the submillimeter papilla of lotus has not been well studied. In this study, it is found that the optimal distribution of submillimeter papilla can effectively prevent the rupture of lotus leaf. Under loading, the submillimeter papilla transfers the stress into its root region, which effectively keeps the leaf broadly intact and collaborates to realize relative functions with micropapilla. Further study by integrating the simulations and biofabricated membrane with artificial submillimeter papilla indicates the contribution of submillimeter papilla on the mechanical property. This study opens a novel avenue for designing strength membrane materials, which has potential applications in the fields of soft robot, electronic device, and packaging.

Mapping the expression of beam hardening artefacts produced by metal posts positioned in different regions of the dental arch.

To objectively assess the expression and direction of artefacts in the vicinity of metal posts positioned in different mandibular regions. A human mandible had two sockets prepared-anterior and posterior regions-to accommodate a single-rooted tooth. Two CBCT units, Picasso Trio and OP300, were used. CBCT images of the tooth without metal post, and with silver-palladium, nickel-chromium, or cobalt-chromium posts (experimental groups) were individually acquired. Then, 8 lines of interest (LOIs) were determined around the root canal, in an axial reconstruction: 4 in orthogonal (buccal, lingual, mesial, and distal) directions, and 4 in oblique (mesiobuccal, distobuccal, mesiolingual, and distolingual) directions. The mean of gray values was measured for each LOI. For the OP300, in general, all experimental groups showed greater expression of hyperdense streaks in orthogonal LOIs and greater expression of hypodense streaks in oblique LOIs. For the Picasso Trio, for both mandibular regions, the buccal LOI showed greater expression of hypodense streaks; conversely, greater expression of hyperdense streaks was observed in the distal and distobuccal LOIs in the anterior region and in the mesiolingual LOI in the posterior region. The silver-palladium group showed significantly greater expression of beam hardening artefacts in the posterior region of the mandible, regardless of the CBCT unit (p < 0.05). The mandibular posterior region showed significantly lower gray values than the anterior region (p < 0.05). The expression and direction of artefacts produced in the vicinity of metal posts vary according to the mandibular region, composition of the post, and CBCT unit. The mapping of artefacts produced by metal posts reveals the root regions with greater expression of hypodense and hyperdense artefacts, which may contribute to recognizing regions more likely to mimic or hide root fracture lines.

Effect of Silver Antibacterial Agents on Bond Strength of Fiber Posts to Root Dentin.

This study was conducted to evaluate whether antibacterial pretreatment irrigation with silver nanoparticles (SNPs) and silver diamine fluoride (SDF) has any effect on bond strength of fiber posts cemented with three types of resin cements in root canal space. Fifty-four endodontically treated maxillary central incisor roots were prepared for fiber post (FRC Postec Plus NO.3, Ivoclar Vivadent) cementation and divided into nine groups in terms of three cement types and two pretreatments with silver antibacterial agents. The cements were as follows: an etch-and-rinse cement (ER, Excite DSC/Variolink N), a self-etch cement (SE, ED Primer/Panavia F2.0), and a self-adhesive cement (SA, Panavia SA Luting Plus). For each cement, the control group was with no treatment and two experimental groups were with SNPs and SDF treatments that were used after acid-etching for ER cement and after EDTA treatment for SE and SA cements. After fiber post cementation, each bonded root was horizontally sectioned into 1-mm thickness microslices to create two slices for each root region (apical, middle and coronal) and underwent push-out bond strength (PBS) test. Data in MPa were analyzed with two-way ANOVA and Tukey test (p=0.05). The interaction of the pretreatment type and cement type was significant (p<0.001). SNPs and SDF significantly increased PBS with ER cement (p≤0.04). This positive effect was also marginally significant for SDF with SE cement (p=0.049). For SA cement, SNPs showed a significant positive effect, but SDF had a significant adverse effect on PBS (p<0.001). The effect of pretreatment with silver antibacterial agents prior to adhesive cementation of fiber posts depends on the resin cement used. Contrary to SNPs with beneficial or no significant effect on bonding for all cements, SDF exhibited a deleterious effect with self-adhesive cement.

Investigations on microstructural and mechanical properties of friction stir welded AA 2024-T351

Abstract In the present study, AA 2024-T351 plates with a thickness of 6 mm were joined using the friction stir welding technique with three different tool rotational speeds and two different pin profiles. Microstructural features and mechanical properties of welded joints were investigated. The grains in recrystallized regions along the stir zone were observed to be almost with invariable sizes. The grain size was revealed to increase with the increase in tool rotational speed. The average grain size was observed to dramatically increase from 2.3 μm to 5.6 μm for welded joints produced with pentagonal shaped pin. All the welded joints were observed to contain defects; the presence of defects exhibited a negative effect on the tensile properties of the welded joint. Most of the defects were observed to localize at the root region of joints. The joint, welded with the tool rotational speed of 250 rpm using pentagonal shaped pin, exhibited ultimate tensile strength with a value of 365 MPa. The ultimate tensile strength of welded joints was found to be higher with the decrease in the tool rotational speed. The welding efficiency of joints was compared with the ultimate tensile strength of base metal; notably, welding efficiency values between 46 % and 80 % were achieved. Microstructural characterizations revealed that Al2Cu (θ phase), Al2CuMg (S phase), and AlCuFeMnSi, Al7Cu2Fe intermetallic particles were dispersed in the stir zone.

Comparison of dentin penetration ability of different root canal sealers used with different obturation methods.

This in vitro study aimed to investigate the tubular penetration depth of four different sealers used with two different obturation methods in the apical, middle, and coronal root canal dentin. Eighty-four single-rooted teeth were instrumented until the F4 ProTaper universal rotary file and filled with AH26, AH Plus (Dentsply, DeTrey, Konstanz, Germany), RealSeal (SybronEndo, Orange, CA), and MTA Fillapex (Angelus, Londrina, Brazil) using cold lateral condensation (CLC) and single-cone (SC) obturation techniques. Thereafter, the roots were sectioned longitudinal and prepared for scanning electron microscope evaluation. The maximum and minimum sealers penetration depth into dentinal tubules at the apical, middle, and coronal regions and the average depth of sealer penetration were calculated. The data was statistically analyzed two-way ANOVA and post hoc Tukey and Dunnett tests and independent samples t test using maximum mean values. There was no statistically difference between the obturation methods (p > .05). When the sealers are evaluated within themselves AH26 was affected by obturation methods significantly (p < .05). Also the results revealed a significant difference between root regions (p < .05). AH26 and RealSeal root canal sealers had the highest penetration values with CLC and SC obturation techniques, respectively. The obturation method did not affect the penetration amount of root canal sealers. RealSeal root canal sealer performed better penetration ability than the other sealers. Apical third of the root in all groups showed lowest penetration depth.

Rhinoplasty With Hyaluronic Acid: A Standard 5-step Injection Procedure Using Sharp Needle.

To explore the clinical effect of rhinoplasty with a standard 5-step injection procedure of hyaluronic acid using sharp needle in correction of deficient features of the Chinese nose. Between January 2016 and December 2018, hyaluronic acid was injected with the sharp needle by a standard procedure in the anterior nasal spine, nasal columella, nasal tip, nasal root, and dorsum, as well as the junction region of nasal root and brow in 198 Chinese patients. The postoperative curative effect was analyzed, and the adverse reactions were observed. The nasal shape in all patients was significantly improved, obtaining the stereoscopic appearance, and satisfactory results. During a 6-month follow-up, 4 patients developed local subcutaneous congestion and bruising in the nasal dorsum after treatment, which disappeared within 2 weeks. No patients suffered from complications such as infection, embolism, necrosis, transparent nasal dorsum, and widened nasal roots. Injection of hyaluronic acid with the sharp needle by a standard 5-step procedure is a safe technique that can effectively correct the deficient features of the Chinese nose.

Estimation of loss factor based on the load share model in improved bending strength spur gear drive system

This paper demonstrates the prediction of loss factor for non-standard gear drives with equal stresses in the root region of the pinion and wheel. This implementation of equal stresses in the root region is achieved in the described model of a spur gear drive with higher transmission ratio using non-standard rack cutter. The aim is to discover the optimal modification point in the tooth profile by varying values of tooth thickness with at most balanced stresses in the gear pair considered for the study. A loss factor is predicted along the path of contact for a complete meshing cycle using finite element method. This paper studies and compares the distinct models and thereby identifies the suitable and appropriate models. The predicted loss factor includes the distribution of load sharing effect during the meshing which is excluded in the compared models. The gear pair is analyzed, and the loss factor is predicted for influence over the major drive parameters. It was observed that the approach employed facilitate substantial enhancement in the efficiency which is confined by the detailed parametric study and numerical simulation of the balanced stresses in the drive.

Fatigue properties of AA6060‐T6 butt welds made by hybrid metal extrusion &amp; bonding

AbstractThe present investigation is concerned with high‐cycle axial fatigue testing of a 2‐mm AA6060‐T6 hybrid metal extrusion &amp; bonding (HYB) butt weld produced in the solid state using AA6082 filler metal addition. The results complement the three‐point bend testing and the tensile testing done in two previous studies. In this study, optical microscope and scanning electron microscope examinations have been carried out to reveal the joint macro/microstructure and document possible surface and root defects deemed to affect fatigue life. In the as‐welded condition, the HYB weld suffers from surface irregularities at the weld face and ‘kissing’ bond formation in the root region. Despite of this, the subsequent testing shows that the fatigue properties exceed those reported for comparable AA6082‐T6 gas metal arc butt welds and matching those reported for corresponding high‐strength laser beam and friction stir weldments.

Hierarchical structure of Five-shu points and Source-point of Triple Energizer Meridian in rabbits

To study the position and hierarchical structure of Five-shu points, i．e., "Guanchong" (TE1), "Yemen" (TE2), "Zhongzhu" (TE3), "Yangchi" (TE4) and "Zhigou" (TE6), and the Source-point "Tianjing" (TE10) of the Triple Energizer (TE) Meridian in the rabbit. Based on WHO Standard Acupuncture Point Locations in the Western Pacific Region (WHO Standard) and National Standard (GB/T 22103-2008) for Acupuncture Point Locations in human body, and combined with X-ray images, the hierarchical structure of Five-shu points and Source-point of the TE Meridian were observed in ten New Zealand rabbits. The acupoint locations were determined by comparing the same name tissues of the rabbits and human body after dissecting the above-mentioned acupoints. After inserting acupuncture needles into the aforementioned acupoints, the relationship between the acupuncture needle and adjacent structure were dissected and measured. "Guanchong" (TE1) was located on the lateral side of the 4th terminal phalanx, and behind the corner of the onyx root. When needled, the penetrated tissues of the acupuncture needle are skin, superficial fascia, deep fascia, and the root region of the 4th phalanx, respectively. "Yemen" (TE2) was located between the 4th and 5th onyxes, at the depression of intersection of coat hair superior to the fingerweb edge. When needled, the penetrated tissues of the acupuncture needle are the superficial fascia, deep fascia and lumbrical muscles of the forepaw, respectively. "Zhongzhu" (TE3) was located between the 4th and 5th metacarpal bones, at the depression proximal to the 4th metacarpophalangeal joint. When needled, the penetrated tissues are skin, superficial fascia, deep fascia, and lumbrical muscle, respectively. "Yangchi" (TE4) was positioned at the dorsal side of the forepaw, and the surface connection line between the accessory and radial bones intersected with the depression of the extensor digitorum communis on the ulnar side. When needled, the penetrated tissues are skin, superficial fascia, deep fascia, and the ulnar side of the common extensor tendon, respectively. "Zhigou" (TE6) was positioned between the radius and ulna, on the posterior aspect of the forelimb and 3 Bone-cun proximal to the distal dorsal forepaw crease. When needled, the penetrated tissues are skin, superficial fascia, deep fascia, and the extensor digitorum, respectively. "Tianjing" (TE10) was located at the junction of the body of humerus and the lateral condyle of humerus, on the posterior aspect of the elbow and proximal to the prominence of the olecranon. When needled, the penetrated tissues are skin, superficial fascia, deep fascia, and triceps brachii muscle, respectively. The Five-shu points and Source-point of the TE Meridian on the forelimb in rabbits are innervated by the cutaneous branches of the ulnar radial nerve and the medial brachial cutaneous nerve at the superficial layer, and by the branches of the ulnar nerve and radial nerve in the deep layer, accompanied with cephalic vein and forearm blood vessels and their branches.

Sustainable agriculture in Africa: Plant growth-promoting rhizobacteria (PGPR) to the rescue

The continued increase in the world's population is expected to make global food availability as one of the major concerns of our future. Nowhere are the concerns greater than in Africa. With a poor economy, the continent is expected to be home to many people in the next few years. Today, agriculture is faced with critical challenges of land degradation, reduced productivity, and susceptibility to abiotic and biotic stresses. To fight this threat, it is crucial to increase agricultural productivity within the next few decades. Given this, agricultural systems that are more sustainable and eco-friendly are being adopted. Recent insight reveals that plant growth-promoting bacteria, especially those residing in the root region (rhizosphere), may play a role in maintaining sustainable agricultural practices. Issues arising from the use of plant growth-promoting rhizobacteria (PGPR) are discussed alongside recent trends in plant microbiome studies. It is envisioned that PGPR will take over the place of synthetic compounds in agriculture, horticulture, silviculture, and approaches in the cleaning up of environmental pollutants. In this review, the roles of PGPR, utilization challenges in Africa and possible solutions are discussed.

The flow past a flatback airfoil with flow control devices: benchmarking numerical simulations against wind tunnel data

Abstract. As wind turbines grow larger, the use of flatback airfoils has become standard practice for the root region of the blades. Flatback profiles provide higher lift and reduced sensitivity to soiling at significantly higher drag values. A number of flow control devices have been proposed to improve the performance of flatback profiles. In the present study, the flow past a flatback airfoil at a chord Reynolds number of 1.5×106 with and without trailing edge flow control devices is considered. Two different numerical approaches are applied, unsteady Reynolds-Averaged Navier Stokes (RANS) simulations and detached eddy simulations (DES). The computational predictions are compared against wind tunnel measurements to assess the suitability of each method. The effect of each flow control device on the flow is examined based on the DES results on the finer mesh. Results agree well with the experimental findings and show that a newly proposed flap device outperforms traditional solutions for flatback airfoils. In terms of numerical modelling, the more expensive DES approach is more suitable if the wake frequencies are of interest, but the simplest 2D RANS simulations can provide acceptable load predictions.

Experimental study on shaped steel shear connectors used in large-scale composite structures

Steel–concrete–steel (SCS) composite structures are used in immersed tunnels and are superior in capacity, constructional facility, etc. in comparison with traditional structures. L- and T-shaped shear connectors are two typical types of shear connectors used in the composite structures. To investigate the mechanical performances of the connectors, 12 groups of push-out tests were conducted. Interfacial slip, bending deformation of the connector web, and strains on the concrete, were measured. Failure modes of concrete crushing were observed in all tested specimens. Evoked outcomes indicated that the performances of the L- and T-shaped connectors were controlled by the non-reinforced concrete. The strain measured in the tests indicated that stress concentration and concrete crushing were mainly located at the root regions. The shear-force–slip relationship, strain distribution, etc., were further analyzed and discussed. Accordingly, the currently available methods used to evaluate the ultimate strength are discussed. These methods were found to be accurate in the case of the L-shaped shear connectors but too conservative for T-shaped shear connectors. A scaling factor was proposed for modification. Finally, 122 groups testing data was collected for validation, which proved that the modified method has adequate accuracy and can be used in various design applications. The experiment data of the L-shape and T-shape shear connectors with different experimental methods were studied which shows the push-out specimens and beam specimens have similar performance. The results of the experimental study and theoretical analyses indicate that the L-shape and T-shape shear connectors have similar mechanical properties while the T-shape shear connectors have better performance concerning the shear stiffness and the ultimate shear strength.

GhMATE1 expression regulates Aluminum tolerance of cotton and overexpression of GhMATE1 enhances acid soil tolerance of Arabidopsis

The ionic form of Aluminum (Al3+) is one of the dangerous metals to the plants under acid soil condition. A principal functional tool of plant Al tolerance encompasses Al-induced stimulation of membrane transporters, which accelerates the organic acid release from the root region. The released organic acid (usually citrate, oxalate and malate) form stable and nontoxic complexes with Al in the rhizosphere. Several genes were characterized to understand the acid soil tolerance mechanisms of plants. In particular, Al-activated malate and citrate discharge from the roots are effectively involved in acid soil stress tolerance mechanisms. Based on the above mechanisms, in this present work, the cotton citrate (GhMATE1 [Multidrug and Toxic compound Extrusion]) transporters has been cloned and characterized in Cotton. Down-regulation of GhMATE1 (GhMATE1-RNAi) system increased the sensitivity to Al and proton. Moreover, plants lacking GhMATE1 released negligible amount of citrate when compared with control plants. The primary and secondary root growth of GhMATE1-RNAi-lines was significantly inhibited under Al stress conditions. Besides, Al stress responsive genes like GhALMT1 (Aluminum-activated Malate Transporter 1), GhSTOP1 (Sensitive to Proton toxicity 1) and GhALS3 (Aluminum Sensitive 3) were not affected in GhMATE1-RNAi lines. In addition, transgenic Arabidopsis plants overexpressing GhMATE1 exhibited Al tolerant phenotypes and these transgenic plants displayed accelerated root growth and enhanced citrate excretion when compared with control plants. The results pointed out that the GhMATE1 expression is Al inducible and controls the citrate-mediated Al3+ sequestration. These observations indicated that GhMATE1 is a key gene which is involved in Al induced citrate release and lateral root growth arrest.

Dislodgement resistance and adhesive pattern of different endodontic sealers to dentine wall after artificial ageing: an in-vitro study.

To compare the dislodgement resistance and the adhesive pattern of four different endodontic sealers to root dentine walls. Ninety lower premolars were assigned to five groups (n = 18), Group 1: no sealer (control); Group 2: EndoRez (ERZ); Group 3: Sealapex (SPX); Group 4: EndoSeal MTA (ESA) and Group 5: BioRoot RCS (BRS). They were instrumented up to size 30 taper 0.06 and obturated using single cone technique with matched-taper gutta-percha cones and one of the mentioned sealers. Six teeth from each group were then randomly subjected to 100, 1000 and 10,000 thermocycles, respectively. 1mm slice of mid root region, measuring 6mm from the apical foramen was prepared and subjected to push-out test under a Universal Testing Machine. Adhesive patterns of sealers were assessed using a stereomicroscope at 20 × magnification and classified using a new system. Statistical analyses were performed using two-way ANOVA, complemented by Tukey HSD and Chi-square tests. ESA and BRS showed significantly higher (p < 0.05) push-out bond strength, followed by SPX, ERZ and lastly the control, but no significant difference was noted between ESA and BRS (p > 0.05) at 100, 1000 and 10,000 thermocycles, respectively. Both ESA and BRS exhibited a significant higher rate (p < 0.05) of Type 3 and Type 4 adhesive patterns as the thermocycles increased. ESA and BRS demonstrated higher bond strength and better adhesive pattern to root dentine wall than SPX and ERZ, especially after artificial ageing.

A Comprehensive Biophysical Model of Ion and Water Transport in Plant Roots. III. Quantifying the Energy Costs of Ion Transport in Salt-Stressed Roots of Arabidopsis.

Salt stress defense mechanisms in plant roots, such as active Na+ efflux and storage, require energy in the form of ATP. Understanding the energy required for these transport mechanisms is an important step toward achieving an understanding of salt tolerance. However, accurate measurements of the fluxes required to estimate these energy costs are difficult to achieve by experimental means. As a result, the magnitude of the energy costs of ion transport in salt-stressed roots relative to the available energy is unclear, as are the relative contributions of different defense mechanisms to the total cost. We used mathematical modeling to address three key questions about the energy costs of ion transport in salt-stressed Arabidopsis roots: are the energy requirements calculated on the basis of flux data feasible; which transport steps are the main contributors to the total energy costs; and which transport processes could be altered to minimize the total energy costs? Using our biophysical model of ion and water transport we calculated the energy expended in the trans-plasma membrane and trans-tonoplast transport of Na+, K+, Cl−, and H+ in different regions of a salt-stressed model Arabidopsis root. Our calculated energy costs exceeded experimental estimates of the energy supplied by root respiration for high external NaCl concentrations. We found that Na+ exclusion from, and Cl− uptake into, the outer root were the major contributors to the total energy expended. Reducing the leakage of Na+ and the active uptake of Cl− across outer root plasma membranes would lower energy costs while enhancing exclusion of these ions. The high energy cost of ion transport in roots demonstrates that the energetic consequences of altering ion transport processes should be considered when attempting to improve salt tolerance.