Root Axis Research Articles

MAP65‐1 and MAP65‐2 promote cell proliferation and axial growth in Arabidopsis roots

We investigated the role of the Arabidopsis microtubule associated proteins 65-1 and 65-2 (MAP65-1 and MAP65-2) in the control of axial root growth. Transgenic plants expressing fluorescent fusion proteins from native promoters indicated exactly overlapping accumulation of MAP65-1 and MAP65-2 in the root tip and elongation zone. Nearly identical protein accumulation patterns were observed when MAP65-1 and MAP65-2 were expressed behind a constitutive CaMV 35S promoter, suggesting a level of post-transcriptional control that restricts these proteins to rapidly growing portions of the root. Co-expression of MAP65-1 and MAP65-2 fusion proteins showed precise co-localization to interphase and cytokinetic microtubule arrays. In interphase root tip cells, the fluorescent protein fusions labeled microtubules that were organized into a variety of different array patterns. In the rapidly growing cells of the root elongation zone, we found MAP65-1 and MAP65-2 co-localized exclusively to the lateral faces of cells that were axially extending. Genetic analysis showed that MAP65-1 and MAP65-2 are coordinately required for proper root elongation. Double map65-1-1 map65-2-2 mutant roots from dark-grown plants contained 50% fewer cells per file than wild-type roots, but we found no evidence that cytokinesis was disrupted. We additionally discovered that cell length was significantly shorter in the mature regions of the root beyond the zone where MAP65-1 and MAP65-2 accumulated. Our data indicate that MAP65-1 and MAP65-2 play a critical role in root growth by promoting cell proliferation and axial extension.

Esthetic orthodontic treatment with a double J retractor and temporary anchorage devices

This clinical article reports an esthetic treatment option for managing a Class II malocclusion in an adult. The patient, a woman aged 24 years 2 months, had crowding and a convex profile. She was treated with maxillary first premolar extractions, a double J retractor, and temporary skeletal anchorage devices in the maxillary arch. Posttreatment records after 2 years showed excellent results with good occlusion and long-term stability.

Sealing ability comparison of mineral trioxide aggregate in root-end cavities prepared with ultrasonic and Er,Cr:YSGG laser

The aim of this study was to compare apical microleakage subsequent to filling of root-end cavities, prepared by either ultrasonic or erbium, chromium:yttrium, scandium, gallium, garnet (Er,Cr:YSGG) laser, with mineral trioxide aggregate (MTA). Microleakage following root-end filling has a direct effect on the outcome of surgical endodontic treatment; therefore, any procedure contributing to adequate sealing of the apical part of the root should be performed. Forty eight human maxillary anterior teeth were selected for this study. After cleaning, shaping and obturation of teeth with gutta-percha and AH26 sealer, 3 mm of the root ends were resected perpendicular to the long axis of roots. The teeth were randomly divided into two experimental (n=20) and two control (n=4) groups. Root-end cavities were prepared by ultrasonic and Er,Cr:YSGG laser (parameters: 4 W, 55% water and 65% air) methods. A protein leakage model was used for evaluation. Data were analyzed using one-way analysis of variance (ANOVA) and a post hoc Tukey test at p<0.05. The mean values of protein microleakage in the laser and ultrasonic groups were 0.0340 ± 0.0053 and 0.0495±0.0276 mg/mL, respectively, with statistically significant differences between the groups (p<0.001). Based on the results of this study, sealing ability of MTA in root-end cavities prepared with Er,Cr:YSGG laser was better than that in cavities prepared with conventional ultrasonic technique. Key words: Apical surgery, dental lasers, MTA, root filling materials, ultrasonic.

Demonstration of osmotically dependent promotion of aerenchyma formation at different levels in the primary roots of rice using a ‘sandwich’ method and X-ray computed tomography

The effect of environmental factors on the regulation of aerenchyma formation in rice roots has been discussed for a long time, because aerenchyma is constitutively formed under aerated conditions. To elucidate this problem, a unique method has been developed that enables sensitive detection of differences in the development of aerenchyma under two different environmental conditions. The method is tested to determine whether aerenchyma development in rice roots is affected by osmotic stress. To examine aerenchyma formation both with and without mannitol treatment in the same root, germinating rice (Oryza sativa) caryopses were sandwiched between two agar slabs, one of which contained 270 mm of mannitol. The roots were grown touching both slabs and were thereby exposed unilaterally to osmotic stress. As a non-invasive approach, refraction contrast X-ray computed tomography (CT) using a third-generation synchrotron facility, SPring-8 (Super photon ring 8 GeV, Japan Synchrotron Radiation Research Institute), was used to visualize the three-dimensional (3-D) intact structure of aerenchyma and its formation in situ in rice roots. The effects of unilateral mannitol treatment on the development of aerenchyma were quantitatively examined using conventional light microscopy. Structural continuity of aerenchyma was clearly visualized in 3-D in the primary root of rice and in situ using X-ray CT. Light microscopy and X-ray CT showed that the development of aerenchyma was promoted on the mannitol-treated side of the root. Detailed light microscopic analysis of cross-sections cut along the root axis from the tip to the basal region demonstrated that aerenchyma developed significantly closer to the root tip on the mannitol-treated side of the root. Continuity of the aerenchyma along the rice root axis was morphologically demonstrated using X-ray CT. By using this 'sandwich' method it was shown that mannitol promoted aerenchyma formation in the primary roots of rice.

Root characteristics of C4 grasses limit reliance on deep soil water in tallgrass prairie

C4 grass species in the mesic tallgrass prairie of central North America can exhibit both high root production and deep rooting in the soil profile (>2 m). Differences in root growth and the types of roots produced vary according to local environmental gradients and management practices. The production of deep roots in tallgrass prairie has been historically presumed as a mechanism for water uptake when surface soils are dry. We examined changes in root biomass, total root length, root width, and theoretical hydraulic conductivity using roots collected from deep soil cores in upland and lowland topographic positions in grazed and ungrazed watersheds of the Konza Prairie Biological Station in north-eastern Kansas, USA. Root biomass, total root length, and theoretical hydraulic conductivity were highest in roots found in the top 20 cm of the soil profile, and then declined exponentially with increasing soil depth. Compared to grazed areas, ungrazed locations had more root biomass and total root length of roots in the most superficial soil layers. No differences in rooting profiles were present among topographic contrasts. Theoretical hydraulic conductivity of axial root xylem did not vary by topographic position or grazing contrasts, and declines in conductivity by depth were driven by changes in the number of vessels per stele, rather than changes in vessel size. Irrespective of differences by grazing treatment or topographic position, significant reductions in root biomass, total root length, and theoretical hydraulic conductivity of grass roots at soil depths greater than 1 m suggest deep roots in this grassland have limited functional significance for water uptake.

Vibration Characteristics of Steam Turbine Blades with Straddle Mount (Effect of Contact Condition on Vibration Characteristics)

There are several kinds of blade root structures to support centrifugal forces acting on steam turbine blades such as straddle mount type root, T-root, axial or side entry root and fork type root. Steam turbine blades are surrounded by contact surfaces at a cover and the above blade root. It is known that contact conditions affect vibration characteristics of turbine blades. In this paper, the effects of contact surfaces on vibration characteristics of steam turbine blades with straddle mount type root were investigated. For that purpose, developed analysis method was applied, and natural frequencies and non-linear frequency responses of a steam turbine blade with contact surfaces at the cover and straddle mount type root were obtained using this method. From these results, it was concluded as follows. (1) Natural frequencies of the blade gradually decrease with increasing rotation speed due to the variation of contact area of the blade root. (2) The effect of friction damping at the cover was dominant and the effects at others were small. To verify these results, natural frequencies and dynamic responses of the blades during rotation were obtained in a spin pit test. Calculated results showed good agreement with experiment results and the analysis method was verified.

Amino acids are a nitrogen source for sugarcane.

Organic forms of nitrogen (ON) represent potential N sources for crops and an alternative to inorganic N (IN, ammonium nitrate). Sugarcane soils receive organic harvest residues (~40-100kg ON ha-1), but it is unknown whether ON is a direct N source for crops. We investigated whether sugarcane can use organic monomers in the form of amino acids and whether the use of amino acids as a N source results in distinct metabolic or morphological change when compared with use of inorganic N (IN). Plantlets cultivated in sterile culture and young plants grown in non-sterile soil culture were supplied with IN, ON (five amino acids present in sugarcane soils), or combined IN and ON. All treatments resulted in similar biomass and N content indicating that sugarcane has a well developed capacity to use ON and confirms findings in other species. ON-supplied plants in axenic culture had increased total branch root length per unit primary root axis which has not been reported previously. In both experimental systems, ON supplied plants had increased asparagine concentrations suggesting altered N metabolism. Root of ON-supplied soil-grown plants had significantly reduced nitrate concentrations. We interpret the shift from nitrate to asparagine as indicative of N form use other than or in addition to nitrate by sugarcane. N metabolite profiling could advance knowledge of crop N sources and this will aid in development of N efficient cropping systems with a reduced N pollution footprint.

Toward a Systems Analysis of the Root

During the past 20 years, our work on root development has been influenced by and has contributed to three biological approaches: molecular genetics, genomics, and systems biology. Characterization of mutations that affect root radial patterning led to the identification of a transcription factor that acts as both a signaling molecule and a key developmental regulator. Combining cell sorting with microarray analysis provided a platform for determining genome-wide expression profiles of mRNAs under standard and stress conditions, revealing a vast amount of tissue-specific response. A focus on connections among molecular components identified a tissue-specific gene regulatory network and a clock-like process that determines the position of lateral roots along the primary root axis. Finally, the genetic basis for the physical network of different roots that constitutes root system architecture is being dissected using automated imaging of growing root systems.

Effect of ABT on Root Growth and Seedling Survival of Haloxylon ammodendron

The effects of ABT3 on the fine root dynamics of seedlings,morphological characteristics of root system at the end of growing season and survival rate of seedlings of Haloxylon ammodendron were studied.The plants were cultivated under natural conditions with four ABT3 treatments,i.e.25,50,100 and 200 mg L-1of ABT3.A random block design was used in the experiment.The results showed that:(1) There were two growth peaks of the fine roots growth of the seedlings which appeared in June and September to October.After ABT treatment,the growth dynamics of fine roots of seedlings was consistent with the control.However,ABT treatment significantly increased the total length of fine roots,growth rate and the number of fine roots.(2) Survival rate of seedlings and root characteristics were closely related,and the regression analysis showed that the underground biomass,root volume,root surface-area,length of axial root and above ground biomass were positively correlated with the seedling survival rate.This result indicated that increasing root growth resulted in the enhancement of seedling survival rate.(3) The results of the principal component analysis suggested that the best treatment was 50 mg L-1of ABT which was inoculated in June in local areas.Fig 2,Tab 3,Ref 31

High-resolution chemical imaging of labile phosphorus in the rhizosphere of Brassica napus L. cultivars

Phosphorus is a major limiting factor in plant growth and crop production. Phosphorus solubilisation, uptake by plant roots and efflux lead to complex, dynamic cycling of P in the vicinity of plant roots. However, direct observation of P dynamics in the rhizosphere at relevant spatial scales (sub-mm) is still lacking. Chemical imaging of the dissolved P concentration around Brassica napus roots was accomplished using diffusive gradients in thin films (DGT) coupled with laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Mathematical simulations served for investigating the capabilities of the chemical imaging technique. We show here, for the first time, localised P release along root axes and at root apices. Our results point at differential P uptake efficiencies of the two investigated B. napus cultivars. This study advances the current understanding of P dynamics in the rhizosphere and thus of plant P nutrition. This technique can serve to unravel the genotypic effects on rhizosphere mobilisation of P and hence assist breeding of highly P efficient crop cultivars.

Ecological adaptation of root architecture to grassland degradation in &lt;I&gt;Potentilla acaulis&lt;/I&gt;

Aims Our objectives were to 1) examine the ecological adaptability of Potentilla acaulis to grassland degrada- tion from the perspective of root architecture, 2) reveal why it can be a dominant species in extremely degraded grassland and 3) discuss its important roles in vegetation restoration or succession and preventing grassland from desertification. Methods We collected relatively complete P. acaulis roots by trenching. The numbers of first vertical roots, length of horizontal root tillering and number of plant tillers were recorded in the field. The root analysis system of WinRHIZO was used to determine total root length, root surface area, total root volume, root average diameter, number of furcations, average branching angle, number of root axes, length of root axes, number of root tips, number of first lateral roots, length of first lateral roots, number of secondary lateral roots, length of secondary lateral roots, root diameters along root length, root surface area and root volume. The data were analyzed by one-way ANOVA and principal component analysis. Important findings In degraded grassland typified by Stipa grandis, the function of P. acaulis became more important in the community and its root range, root depth, the number of first vertical roots, the number of plant tillers and the length of horizontal root tillering increased significantly. The parameters of root surface area, length of secondary lateral roots, total root length and the number of furcations explained the adaptability of P. acaulis to grassland degradation. Roots with a diameter <2 mm had a significant effect on root surface area and total root length of single plants of P. acaulis. The three-dimensional root architecture of a broad-waist-inverted centrum was an advantageous configuration for P. acaulis to adapt for grassland degradation and can explain P. acaulis as a

Effects of mechanostimulation on gravitropism and signal persistence in flax roots

Gravitropism describes curvature of plants in response to gravity or differential acceleration and clinorotation is commonly used to compensate unilateral effect of gravity. We report on experiments that examine the persistence of the gravity signal and separate mechanostimulation from gravistimulation. Flax roots were reoriented (placed horizontally for 5, 10, or 15 min) and clinorotated at a rate of 0.5 to 5 rpm either vertically (parallel to the gravity vector and root axis) or horizontally (perpendicular to the gravity vector and parallel to the root axis). Image sequences showed that horizontal clinorotation did not affect root growth rate (0.81±0.03 mm h-1) but vertical clinorotation reduced root growth by about 7%. The angular velocity did not affect growth for either direction. However, maximal curvature for vertical clinorotation decreased with increasing rate of rotation and produced straight roots at 5 rpm. In contrast, horizontal clinorotation increased curvature with increasing angular velocity. The point of maximal curvature was used to determine the longevity (memory) of the gravity signal, which lasted about 120 min. The data indicate that mechanostimulation modifies the magnitude of the graviresponse but does not affect memory persistence.

Allometry of root branching and its relationship to root morphological and functional traits in three range grasses.

The study of proportional relationships between size, shape, and function of part of or the whole organism is traditionally known as allometry. Examination of correlative changes in the size of interbranch distances (IBDs) at different root orders may help to identify root branching rules. Root morphological and functional characteristics in three range grasses {bluebunch wheatgrass [Pseudoroegneria spicata (Pursh) Löve], crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult.×A. cristatum (L.) Gaert.], and cheatgrass (Bromus tectorum L.)} were examined in response to a soil nutrient gradient. Interbranch distances along the main root axis and the first-order laterals as well as other morphological and allocation root traits were determined. A model of nutrient diffusivity parameterized with root length and root diameter for the three grasses was used to estimate root functional properties (exploitation efficiency and exploitation potential). The results showed a significant negative allometric relationship between the main root axis and first-order lateral IBD (P ≤0.05), but only for bluebunch wheatgrass. The main root axis IBD was positively related to the number and length of roots, estimated exploitation efficiency of second-order roots, and specific root length, and was negatively related to estimated exploitation potential of first-order roots. Conversely, crested wheatgrass and cheatgrass, which rely mainly on root proliferation responses, exhibited fewer allometric relationships. Thus, the results suggested that species such as bluebunch wheatgrass, which display slow root growth and architectural root plasticity rather than opportunistic root proliferation and rapid growth, exhibit correlative allometry between the main axis IBD and morphological, allocation, and functional traits of roots.

Flexibility in the Patterning and Control of Axial Locomotor Networks in Lamprey

In lower vertebrates, locomotor burst generators for axial muscles generally produce unitary bursts that alternate between the two sides of the body. In lamprey, a lower vertebrate, locomotor activity in the axial ventral roots of the isolated spinal cord can exhibit flexibility in the timings of bursts to dorsally-located myotomal muscle fibers versus ventrally-located myotomal muscle fibers. These episodes of decreased synchrony can occur spontaneously, especially in the rostral spinal cord where the propagating body waves of swimming originate. Application of serotonin, an endogenous spinal neurotransmitter known to presynaptically inhibit excitatory synapses in lamprey, can promote decreased synchrony of dorsal-ventral bursting. These observations suggest the possible existence of dorsal and ventral locomotor networks with modifiable coupling strength between them. Intracellular recordings of motoneurons during locomotor activity provide some support for this model. Pairs of motoneurons innervating myotomal muscle fibers of similar ipsilateral dorsoventral location tend to have higher correlations of fast synaptic activity during fictive locomotion than do pairs of motoneurons innervating myotomes of different ipsilateral dorsoventral locations, suggesting their control by different populations of premotor interneurons. Further, these different motoneuron pools receive different patterns of excitatory and inhibitory inputs from individual reticulospinal neurons, conveyed in part by different sets of premotor interneurons. Perhaps, then, the locomotor network of the lamprey is not simply a unitary burst generator on each side of the spinal cord that activates all ipsilateral body muscles simultaneously. Instead, the burst generator on each side may comprise at least two coupled burst generators, one controlling motoneurons innervating dorsal body muscles and one controlling motoneurons innervating ventral body muscles. The coupling strength between these two ipsilateral burst generators may be modifiable and weakening when greater swimming maneuverability is required. Variable coupling of intrasegmental burst generators in the lamprey may be a precursor to the variable coupling of burst generators observed in the control of locomotion in the joints of limbed vertebrates.

Comparative and correlational studies on contents of flavonoids in axial root and lateral root of Scutellaria baicalensis

To compare the contents of flavonoids in axial root and lateral root of Scutellaria baicalensis, and study their correlation. The contents of 5 major flavonoids, baicalin, wogonoside, baicalein, wogonin and oroxylin A, were determined in axial root and lateral root of S. baicalensis by HPLC. The correlation and regression analysis between the contents of flavonoids in the lateral root and whole root was carried out. The contents of baicalin and wogonoside showed no significant difference among upper part and lower part of the axial root, lateral root and whole part of the root. The contents of baicalein, wogonin and oroxylin A showed a significant difference between upper part and lower part of the axial root. There was only the content of wogonin existing significant difference between lateral root and whole part of the root. The results of the correlation and regression analysis indicated that the contents of flavonoids in the lateral root and whole root were significant positively correlated, the coefficient of determination for all components were quite higher, except for wogonin. The contents of flavonoids are uniformly distributed in axial and lateral root of S. baicalensis. The contents of flavonoids in lateral root could be used to estimate the content of the whole root. The result could be useful for breeding and preserving excellent germplasm at the system breed process for S. baicalensis.

Root growth in response to nitrogen supply in Chinese maize hybrids released between 1973 and 2009

Root growth has a fundamental role in nitrogen (N) use efficiency. Nevertheless, little is known about how modern breeding progress has affected root growth and its responses to N supply. The root and shoot growth of a core set of 11 representative Chinese maize (Zea mays L.) hybrids released between 1973 and 2009 were investigated under high N (4 mmol L(-1), HN) and low N (0.04 mmol L(-1), LN) levels in a solution culture system. Compared with LN, HN treatment decreased root dry weight (RDW), the root: shoot ratio (R/S), and the relative growth rate for root dry weight (RGR(root)), but increased the total root length (TRL) and the total lateral root length (LRL). The total axial root length (ARL) per plant was reduced under HN, mostly in hybrids released before the 1990s. The number of seminal roots (SRN) was largely unaffected by different N levels. More recently released hybrids showed higher relative growth rates in the shoot under both HN and LN. However, the roots only showed increased RGR under HN treatment. Correspondingly, there was a positive linear relationship with the year of hybrid release for TRL, LRL and ARL under HN treatment. Together, these results suggest that while shoot growth of maize has improved, its root growth has only improved under high N conditions over the last 36 years of selective breeding in China. Improving root growth under LN conditions may be necessary to increase the N use efficiency of maize.

Heterosis in rice seedlings: its relationship to gibberellin content and expression of gibberellin metabolism and signaling genes.

Despite the accumulation of data on the genetic and molecular understanding of heterosis, there is little information on the regulation of heterosis at the physiological level. In this study, we performed a quantitative analysis of endogenous gibberellin (GA) content and expression profiling of the GA metabolism and signaling genes to investigate the possible relationship between GA signaling and heterosis for seedling development in rice (Oryza sativa). The materials used were an incomplete diallele set of 3 × 3 crosses and the six parents. In the growing shoots of the seedlings at 20 d after sowing, significant positive correlations between the contents of some GA species and performance and heterosis based on shoot dry mass were detected. Expression analyses of GA-related genes by real-time reverse transcription-polymerase chain reaction revealed that 13 out of the 16 GA-related genes examined exhibited significant differential expression among the F1 hybrid and its parents, acting predominantly in the modes of overdominance and positive dominance. Expression levels of nine genes in the hybrids displayed significant positive correlations with the heterosis of shoot dry mass. These results imply that GAs play a positive role in the regulation of heterosis for rice seedling development. In shoots plus root axes of 4-d-old germinating seeds that had undergone the deetiolation, mimicking normal germination in soil, the axis dry mass was positively correlated with the content of GA₂₉ but negatively correlated with that of GA₁₉. Our findings provide supporting evidence for GAs playing an important regulatory role in heterosis for rice seedling development.

Influence of secondary air mass flow rates on gas/particle flow characteristics near the swirl burner region

In a gas/particle two-phase testing facility with the use of a three-component particle-dynamics anemometer, we determine the influence of secondary air mass flow rates on gas/particle flow characteristics in the near-burner region of a centrally fuel-rich swirl coal combustion burner. Velocities, particle volume flux profiles and normalized particle number concentrations were obtained. The peaks of axial, radial, and tangential mean velocities and root mean square velocities increase as the secondary air mass flow rate increases. Simultaneously, the recirculation zone enlarges accompanied by an increase in swirl number. The peak particle volume flux near the chamber axis, between axial distance x/ d = 0.1–0.7, increases with secondary air mass flow rate although its peak value decreases and the attenuation rate falls faster than other mass flow rates.

Differences in Running Mechanics and Economy between Collegiate Runners and Triathletes Identified Using High-Resolution Accelerometers

We have previously reported differences in economy between trained and untrained runners using high-resolution accelerometers (HRA) and indirect calorimetry. In these runners though, differences may have been due to discrepancies in metabolic fitness level. PURPOSE: To determine if HRA could identify differences in economy and mechanics of running between collegiate runners (XC) and triathletes (TRI), of comparable metabolic fitness, during treadmill locomotion. METHODS: Procedures were approved by the Eastern Michigan University CHHS Human Subject Review Committee and subjects gave informed consent. 23 runners, 16 XC (22.1±1.5yr, 66.5±5.7 kg, 71.1±5.2 ml/kg/min) and 8 TRI (25.6±3.8yr, 70.8±3.7 kg, 66.2±4.2 ml/kg/min) performed incremental VO2max trials while wearing HRA (Microstrain, VT; 617 Hz). Aggregate acceleration for vertical (VT), anterior/posterior (AP), medial/lateral (ML), axes were recorded and Euclidian resultants were computed (RES). Trials consisted of 3 min stages starting at 8kph and increasing 2kph until exhaustion. Group comparisons were made from 10-18kph, as all subjects completed these stages. Axial root mean square (RMS), RMS relative to speed (EC), and ratio of RMS/RES (RA) were compared between XC and TRI to identify differences in running mechanics between groups. Expired gases were collected using an Oxycon Mobile (Viasys, CA). VO2 and RER were used to determine O2 cost (O2C) and energy expenditure (EE). MANOVAs were performed using PASW 17.0 (SPSS; IL) α=.05. RESULTS: Total weekly training time (14.8±2.1 hr) was not different between groups but XC ran significantly more than TRI(13.5±1.9 vs. 5.6±1.5 hr). All HRA parameters (RMS, EC, RA) were significantly greater for XC vs. TRI in VT, and lower (p<.05) for XC vs. TRI in ML and AP, except MLRA. Significant speed by group interactions (p<.05) were also present for all HRA parameters except MLEC and MLRA. RER was not different between groups (.91±0)indicating similar fitness for XC and TRI, but VO2 and EE were significantly higher for TRI vs. XC (47.4±.5 vs. 40.8±.3 ml/kg/min and.23±.0 vs.20±.0 kcal/kg/min). CONCLUSION: These data show that XC accelerate more in the VT but less in the AP than TRI. Therefore improved running economy with training may come more from reduced accelerations in AP than VT or ML.

Physiological and Molecular Response of Wheat Roots to Nitrate Supply in Seedling Stage

The objective of this study was to understand the morphological, physiological, and molecular responses of wheat roots to nitrate supply at seedling stage. Two wheat genotypes, Jimai 22 and Shannong 15, were grown in Hoagland's nutrient solution with different nitrate levels at seedling stage. Results indicated that the plant dry weight and N accumulation increased with the increase of nitrate supply. The number of axial root, total uptake area (TUA), and active uptake area (AUA) increased with more nitrate supply. Correlation analysis indicated that significant positive correlations existed between N accumulation and dry weight, N accumulation and AUA, and N accumulation and AUA/TUA. Although, the expressions of NRT2.1, NRT2.2, and NRT2.3 decreased with nitrate supply increased, the expressions of NRT1, NRT2.1, and NRT2.3 could maintain high level at N3 treatment. The free amino acid and NO 3 − content in shoot also increased with the increased nitrate application, but no significant difference was found in root among the treatments. These results implied that the increase of N uptake by nitrate supply was due to the morphological and physiological responses of wheat roots and the high expression level of TaNRT genes. Similarly, the contribution of morphological, physiological, and molecular parameters was different between two genotypes of wheat.