Cortical cell size regulates root metabolic cost.

It has been hypothesized that vacuolar occupancy in mature root cortical parenchyma cells regulates root metabolic cost and thereby plant fitness under conditions of drought, suboptimal nutrient availability, and increased soil mechanical impedance. However, the mechanistic role of vacuoles in reducing root metabolic cost was unproven. Here we provide evidence to support this hypothesis. We first show that root cortical cell size is determined by both cortical cell diameter and cell length. Significant genotypic variation for both cortical cell diameter (~1.1- to 1.5-fold) and cortical cell length (~ 1.3- to 7-fold) was observed in maize and wheat. GWAS and QTL analyses indicate cortical cell diameter and length are heritable and under independent genetic control. We identify candidate genes for both phenes. Empirical results from isophenic lines contrasting for cortical cell diameter and length show that increased cell size, due to either diameter or length, is associated with reduced root respiration, nitrogen content, and phosphorus content. RootSlice, a functional-structural model of root anatomy, predicts that an increased vacuolar: cytoplasmic ratio per unit cortical volume causes reduced root respiration and nutrient content. Ultrastructural imaging of cortical parenchyma cells with varying cortical diameter and cortical cell length confirms the in silico predictions and shows that an increase in cell size is correlated with increased vacuolar volume and reduced cytoplasmic volume. Vacuolar occupancy and its relationship with cell size merits further investigation as a phene for improving crop adaptation to edaphic stress.

Gradual domestication of root traits in the earliest maize from Tehuacán.

Efforts to understand the phenotypic transition that gave rise to maize from teosinte have mainly focused on the analysis of aerial organs, with little insights into possible domestication traits affecting the root system. Archeological excavations in San Marcos cave (Tehuacán, Mexico) yielded two well-preserved 5,300 to 4,970 calibrated y B.P. specimens (SM3 and SM11) corresponding to root stalks composed of at least five nodes with multiple nodal roots and, in case, a complete embryonic root system. To characterize in detail their architecture and anatomy, we used laser ablation tomography to reconstruct a three-dimensional segment of their nodal roots and a scutellar node, revealing exquisite preservation of the inner tissue and cell organization and providing reliable morphometric parameters for cellular characteristics of the stele and cortex. Whereas SM3 showed multiple cortical sclerenchyma typical of extant maize, the scutellar node of the SM11 embryonic root system completely lacked seminal roots, an attribute found in extant teosinte and in two specific maize mutants: root with undetectable meristem1 (rum1) and rootless concerning crown and seminal roots (rtcs). Ancient DNA sequences of SM10­a third San Marcos specimen of equivalent age to SM3 and SM11­revealed the presence of mutations in the transcribed sequence of both genes, offering the possibility for some of these mutations to be involved in the lack of seminal roots of the ancient specimens. Our results indicate that the root system of the earliest maize from Tehuacán resembled teosinte in traits important for maize drought adaptation.

Cortical parenchyma wall width regulates root metabolic cost and maize performance under suboptimal water availability.

We describe how increased root cortical parenchyma wall width (CPW) can improve tolerance to drought stress in maize by reducing the metabolic costs of soil exploration. Significant variation (1.0-5.0 µm) for CPW was observed in maize germplasm. The functional-structural model RootSlice predicts that increasing CPW from 2 µm to 4 µm is associated with a ~15% reduction in root cortical cytoplasmic volume, respiration rate, and nitrogen content. Analysis of genotypes with contrasting CPW grown with and without water stress in the field confirms that increased CPW is correlated with an ~32-42% decrease in root respiration. Under water stress in the field, increased CPW is correlated with 125% increased stomatal conductance, 325% increased leaf CO2 assimilation rate, 73-78% increased shoot biomass, and 92-108% increased yield. CPW was correlated with leaf mesophyll midrib parenchyma wall width, indicating pleiotropy. Genome-wide association study analysis identified candidate genes underlying CPW. OpenSimRoot modeling predicts that a reduction in root respiration due to increased CPW would also benefit maize growth under suboptimal nitrogen, which requires empirical testing. We propose CPW as a new phene that has utility under edaphic stress meriting further investigation.

Thriving in a salty future: morpho-anatomical, physiological, and molecular adaptations to salt stress in alfalfa (Medicago sativa L.) and other crops.

BACKGROUND: With soil salinity levels rising at an alarming rate, accelerated by climate change and human interventions, there is a growing need for crop varieties that can grow on saline soils. Alfalfa (Medicago sativa) is a cool-season perennial leguminous crop, commonly grown as forage, biofuel feedstock, and soil conditioner. It demonstrates significant potential for agricultural circularity and sustainability, for example by fixing nitrogen, sequestering carbon, and improving soil structures. Although alfalfa is traditionally regarded as moderately salt-tolerant species, modern alfalfa varieties display specific salt-tolerance mechanisms, which could be used to pave alfalfa's role as a leading crop able to grow on saline soils. SCOPE: Alfalfa's salt tolerance underlies a large variety of cascading biochemical and physiological mechanisms. These are partly enabled by alfalfa's complex genome structure and out-crossing nature, which on the other hand entail impediments for molecular and genetic studies. This review first summarizes the general effects of salinity on plants and the broad-ranging mechanisms for dealing with salt-induced osmotic stress, ion toxicity, and secondary stress. Secondly, we address defensive and adaptive strategies that have been described for alfalfa, such as the plasticity of alfalfa's root system, hormonal crosstalk for maintaining ion homeostasis, spatiotemporal specialized metabolite profiles, and the protection of alfalfa-rhizobia associations. Finally, bottlenecks for research of the physiological and molecular salt-stress responses as well as biotechnology-driven improvements of salt tolerance are identified and discussed. CONCLUSION: Understanding morpho-anatomical, physiological, and molecular responses to salinity is essential for the improvement of alfalfa and other crops in saline land reclamation. This review identifies potential breeding targets for enhancing alfalfa performance stability and general crop robustness for rising salt levels as well as to promote alfalfa applications in saline land management.

Multiseriate cortical sclerenchyma enhance root penetration in compacted soils.

Mechanical impedance limits soil exploration and resource capture by plant roots. We examine the role of root anatomy in regulating plant adaptation to mechanical impedance and identify a root anatomical phene in maize (Zea mays) and wheat (Triticum aestivum) associated with penetration of hard soil: Multiseriate cortical sclerenchyma (MCS). We characterize this trait and evaluate the utility of MCS for root penetration in compacted soils. Roots with MCS had a greater cell wall-to-lumen ratio and a distinct UV emission spectrum in outer cortical cells. Genome-wide association mapping revealed that MCS is heritable and genetically controlled. We identified a candidate gene associated with MCS. Across all root classes and nodal positions, maize genotypes with MCS had 13% greater root lignin concentration compared to genotypes without MCS. Genotypes without MCS formed MCS upon exogenous ethylene exposure. Genotypes with MCS had greater lignin concentration and bending strength at the root tip. In controlled environments, MCS in maize and wheat was associated improved root tensile strength and increased penetration ability in compacted soils. Maize genotypes with MCS had root systems with 22% greater depth and 49% greater shoot biomass in compacted soils in the field compared to lines without MCS. Of the lines we assessed, MCS was present in 30 to 50% of modern maize, wheat, and barley cultivars but was absent in teosinte and wild and landrace accessions of wheat and barley. MCS merits investigation as a trait for improving plant performance in maize, wheat, and other grasses under edaphic stress.

Characterization of the root and canal anatomy of maxillary premolar teeth in an Iraqi subpopulation: a cone beam computed tomography study.

This study aims to evaluate the number of roots and root canal morphology types of maxillary premolars in relation to a patient's gender and age in an Iraqi population using two classification systems. Cone beam computed tomography (CBCT) scans of 1116 maxillary premolars from 385 patients were evaluated for the number of roots and root canal morphology types according to Vertucci's classification and Ahmed et al. classification systems. Differences in the number of roots and root canal morphology types with regard to tooth type, patients' gender and age groups were evaluated and the degree of bilateral symmetry was determined. Chi-squared test was used for statistical analysis. About 51.1% of the 1st premolars were double rooted. The majority (87.9%) of the 2nd premolars were single rooted. The three-rooted form presented in only 1.2% and 0.7% of the 1st and 2nd premolars, respectively. Vertucci Type IV (Ahmed et al. code 2MaxP B1P1) and Vertucci Type I (Ahmed et al. code 1MaxP1) were the most common canal morphology types in the 1st and 2nd premolars, respectively. Females showed a lower number of roots and a higher prevalence of Vertucci Type I configuration (P < 0.05). Younger age groups showed a higher prevalence of Vertucci Type I configuration (P < 0.05). Bilateral symmetry was seen in more than half of the maxillary premolars. There is a considerable variation in the number of roots and root canal configurations of maxillary premolars in the studied Iraqi population, with a significant difference by gender and age groups. Ahmed et al. classification provided more accurate presentation of the root and canal anatomy in maxillary premolars compared to Vertucci's classification.

[Impacted third molar root abnormality with mandibular canal close position as a presupposing factor to inferior alveolar nerve trauma]. / Anomalii stroeniya kornei tret'ikh molyarov, tesno prilegayushchikh k nizhnechelyustnomu kanalu, kak predraspolagayushchii faktor travmy nizhnego al'veolyarnogo nerva.

OBJECTIVE: The aim of the study is reducing the risks of surgical injury to the inferior alveolar nerve, by taking into account individual topographic and anatomical features, improving diagnostic methods, and techniques for removing retinated teeth with a close fit to the mandibular canal. MATERIAL AND METHODS: An examination was conducted in the Department of Surgical Dentistry (CBCT/OPG) and surgical treatment of 223 patients, with a close fit of the roots of the retinated lower third molar to the mandibular canal. Microslips of teeth with roots intact during removal (n=96) of the main group and the control group (n=52) were prepared with a Micromet Remet manual petrographic machine. The sections were carried out along the longitudinal axis of the tooth with the capture of the area of close fitting of the nerve, the teeth from the control group were sawed longitudinally along the axis of the root. The measurement of the macroanatomic features of the roots was carried out with a micrometer (MCC-MP-100 0.001 electronic «CHEESE¼, manufactured in the Russian Federation), measurements of the thickness of dentine and cement tissues on macroglyphs were carried out using a microscope calibration ruler with an accuracy of 0.01 mm. RESULTS: In the main group, three types of attachment of the mandibular canal to the root of the third molars were distinguished: 20 (96) cases of inter-root attachment of the mandibular canal, 42 (96) apical, 34 (96) lateral (buccal and lingual). A number of anomalies in the structure of the roots of the third molars have been revealed, which are a factor in injury to the neurovascular bundle of the mandibular canal during tooth extraction. The surface of the roots, as well as the microscopes of the tooth sections adjacent to the mandibular canal, were studied under a microscope. CONCLUSION: A number of specific anomalies of the roots of retinated third molars formed by root dilaceration, thinning of cement tissues, hypercementosis, which are formed at the site of the mandibular canal.In the presence of a deep indentation on the root of the tooth, as well as in the presence of areas of apical hypercementosis in the form of a «spike¼, the probability of nerve injury during tooth extraction increases many times, which must be taken into account when removing retinated third molars.

RootSlice-A novel functional-structural model for root anatomical phenotypes.

Root anatomy is an important determinant of root metabolic costs, soil exploration, and soil resource capture. Root anatomy varies substantially within and among plant species. RootSlice is a multicellular functional-structural model of root anatomy developed to facilitate the analysis and understanding of root anatomical phenotypes. RootSlice can capture phenotypically accurate root anatomy in three dimensions of different root classes and developmental zones, of both monocotyledonous and dicotyledonous species. Several case studies are presented illustrating the capabilities of the model. For maize nodal roots, the model illustrated the role of vacuole expansion in cell elongation; and confirmed the individual and synergistic role of increasing root cortical aerenchyma and reducing the number of cortical cell files in reducing root metabolic costs. Integration of RootSlice for different root zones as the temporal properties of the nodal roots in the whole-plant and soil model OpenSimRoot/maize enabled the multiscale evaluation of root anatomical phenotypes, highlighting the role of aerenchyma formation in enhancing the utility of cortical cell files for improving plant performance over varying soil nitrogen supply. Such integrative in silico approaches present avenues for exploring the fitness landscape of root anatomical phenotypes.

Graphene oxide affected root growth, anatomy, and nutrient uptake in alfalfa.

The increasing application of carbon nanomaterials has resulted in their inevitable release into the environment. Their toxic effects on plant roots require careful investigation. In the present study, alfalfa (Medicago sativa L.) was exposed to graphene oxide (GO) at levels of 0.2 %, 0.4 %, and 0.6 % (w/w) in potting soil. This study aims to better understand the impact of GO on the root growth, structure, and physiology of alfalfa in the soil matrix. The results demonstrated that GO significantly affected the development and structure of alfalfa roots, and the effect varied with GO level. The highest level of GO (0.6 %) reduced the root length, diameter, volume, dry weight, number of lateral roots, and root activity by 36.1 %, 31.3 %, 60.0 %, 89.6 %, 55.8 %, and 72.3 % (p < 0.05), respectively, and the vascular cylinder diameter, periderm thickness, vessel diameter, and phellem thickness decreased by 51.5 %, 50.7 %, 80.9 %, and 49.1 % (p < 0.05), respectively. These observations might be associated with GO-induced oxidative stress, which was indicated by the activity of antioxidant enzymes. Furthermore, high GO levels (0.4 % and 0.6 %) inhibited the uptake of N, P, K, Mg, Zn, Fe, Mo, Si, and B in roots. Our findings indicate that GO at high levels has a negative impact on root growth and development by inducing oxidative stress, structural impairment, and nutritional imbalance. Careful soil GO management should be emphasized.

Maize (Zea mays L.) responses to salt stress in terms of root anatomy, respiration and antioxidative enzyme activity.

BACKGROUND: Soil salt stress is a problem in the world, which turns into one of the main limiting factors hindering maize production. Salinity significantly affects root physiological processes in maize plants. There are few studies, however, that analyses the response of maize to salt stress in terms of the development of root anatomy and respiration. RESULTS: We found that the leaf relative water content, photosynthetic characteristics, and catalase activity exhibited a significantly decrease of salt stress treatments. However, salt stress treatments caused the superoxide dismutase activity, peroxidase activity, malondialdehyde content, Na+ uptake and translocation rate to be higher than that of control treatments. The detrimental effect of salt stress on YY7 variety was more pronounced than that of JNY658. Under salt stress, the number of root cortical aerenchyma in salt-tolerant JNY658 plants was significantly higher than that of control, as well as a larger cortical cell size and a lower root cortical cell file number, all of which help to maintain higher biomass. The total respiration rate of two varieties exposed to salt stress was lower than that of control treatment, while the alternate oxidative respiration rate was higher, and the root response of JNY658 plants was significant. Under salt stress, the roots net Na+ and K+ efflux rates of two varieties were higher than those of the control treatment, where the strength of net Na+ efflux rate from the roots of JNY658 plants and the net K+ efflux rate from roots of YY7 plants was remarkable. The increase in efflux rates reduced the Na+ toxicity of the root and helped to maintain its ion balance. CONCLUSION: These results demonstrated that salt-tolerant maize varieties incur a relatively low metabolic cost required to establish a higher root cortical aerenchyma, larger cortical cell size and lower root cortical cell file number, significantly reduced the total respiration rate, and that it also increased the alternate oxidative respiration rate, thereby counteracting the detrimental effect of oxidative damage on root respiration of root growth. In addition, Na+ uptake on the root surface decreased, the translocation of Na+ to the rest of the plant was constrained and the level of Na+ accumulation in leaves significantly reduced under salt stress, thus preempting salt-stress induced impediments to the formation of shoot biomass.

Using anatomical traits to understand root functions across root orders of herbaceous species in a temperate steppe.

Root anatomical traits play crucial roles in understanding root functions and root form-function linkages. However, the root anatomy and form-function linkages of monocotyledonous and dicotyledonous herbs remain largely unknown. We measured order-based anatomical traits and mycorrhizal colonization rates of 32 perennial herbs of monocotyledons and dicotyledons in a temperate steppe. For monocots, relative constant proportion of cortex and mycorrhizal colonization rates, but increased cell-wall thickening of the endodermis and proportion of stele were observed across root orders, indicating a slight reduction in absorption capacity and improvement in transportation capacity across orders. For dicots, the cortex and mycorrhizal colonization disappeared in the fourth-order and/or fifth-order roots, whereas the secondary vascular tissue increased markedly, suggesting significant transition of root functions from absorption to transportation across root orders. The allometric relationships between stele and cortex differed across root orders and plant groups, suggesting different strategies to coordinate the absorption and transportation functions among plant groups. In summary, our results revealed different functional transition patterns across root orders and distinct strategies for coordinating the absorption and transportation of root system between monocots and dicots. These findings will contribute to our understanding of the root form and functions in herbaceous species.

Field evidence for litter and self-DNA inhibitory effects on Alnus glutinosa roots.

Litter decomposition releases nutrients beneficial to plants but also induces phytotoxicity. Phytotoxicity can result from either labile allelopathic compounds or species specific and caused by conspecific DNA. Aquatic plants in flowing water generally do not suffer phytotoxicity because litter is regularly removed. In stagnant water or in litter packs an impact on root functionality can occur. So far, studies on water plant roots have been carried out in laboratory and never in field conditions. The effect of conspecific vs heterospecific litter and purified DNA were assessed on aquatic roots of the riparian woody species Alnus glutinosa L. using a novel method, using closed and open plastic tubes fixed to single roots in the field with closed tubes analogous to stagnant water. Four fresh and four decomposed litter types were used and analysed on extractable C, cellulose, lignin, N content and using 13 C-CPMAS NMR spectroscopy. Inhibitory effects were observed with fresh litter in closed systems, with a positive correlation with extractable C and negative with lignin and lignin : N ratio. Alnus self-DNA, but not heterologous one, caused acute toxic effects in the closed system. Our results demonstrate the first field-based evidence for self-DNA inhibition as causal factor of negative feedback between plants and substrate.

Root traits for low input agroecosystems in Africa: Lessons from three case studies.

In many regions across Africa, agriculture is largely based on low-input and small-holder farming systems that use little inorganic fertilisers and have limited access to irrigation and mechanisation. Improving agricultural practices and developing new cultivars adapted to these environments, where production already suffers from climate change, is a major priority for food security. Here, we illustrate how breeding for specific root traits could improve crop resilience in Africa using three case studies covering very contrasting low-input agroecosystems. We first review how greater basal root whorl number and longer and denser root hairs increased P acquisition efficiency and yield in common bean in South East Africa. We then discuss how water-saving strategies, root hair density and deep root growth could be targeted to improve sorghum and pearl millet yield in West Africa. Finally, we evaluate how breeding for denser root systems in the topsoil and interactions with arbuscular mycorrhizal fungi could be mobilised to optimise water-saving alternate wetting and drying practices in West African rice agroecosystems. We conclude with a discussion on how to evaluate the utility of root traits and how to make root trait selection feasible for breeders so that improved varieties can be made available to farmers through participatory approaches.

Soil penetration by maize roots is negatively related to ethylene-induced thickening.

Radial expansion is a classic response of roots to a mechanical impedance that has generally been assumed to aid penetration. We analysed the response of maize nodal roots to impedance to test the hypothesis that radial expansion is not related to the ability of roots to cross a compacted soil layer. Genotypes varied in their ability to cross the compacted layer, and those with a steeper approach to the compacted layer or less radial expansion in the compacted layer were more likely to cross the layer and achieve greater depth. Root radial expansion was due to cortical cell size expansion, while cortical cell file number remained constant. Genotypes and nodal root classes that exhibited radial expansion in the compacted soil layer generally also thickened in response to exogenous ethylene in hydroponic culture, that is, radial expansion in response to ethylene was correlated with the thickening response to impedance in soil. We propose that ethylene insensitive roots, that is, those that do not thicken and can overcome impedance, have a competitive advantage under mechanically impeded conditions as they can maintain their elongation rates. We suggest that prolonged exposure to ethylene could function as a stop signal for axial root growth.

Plasticity of root anatomy during domestication of a maize-teosinte derived population.

Maize (Zea mays L.) has undergone profound changes in root anatomy for environmental adaptation during domestication. However, the genetic mechanism of plasticity of maize root anatomy during the domestication process remains unclear. In this study, high-resolution mapping was performed for nine root anatomical traits using a maize-teosinte population (mexicana × Mo17) across three environments. Large genetic variations were detected for different root anatomical traits. The cortex, stele, aerenchyma areas, xylem vessel number, and cortical cell number had large variations across three environments, indicating high plasticity. Sixteen quantitative trait loci (QTL) were identified, including seven QTL with QTL × environment interaction (EIQTL) for high plasticity traits and nine QTL without QTL × environment interaction (SQTL). Most of the root loci were consistent with shoot QTL depicting domestication signals. Combining transcriptome and genome-wide association studies revealed that AUXIN EFFLUX CARRIER PIN-FORMED LIKE 4 (ZmPILS4) serves as a candidate gene underlying a major QTL of xylem traits. The near-isogenic lines (NILs) with lower expression of ZmPILS4 had 18-24% more auxin concentration in the root tips and 8-15% more xylem vessels. Nucleotide diversity values analysis in the promoter region suggested that ZmPILS4 was involved in maize domestication and adaptation. These results revealed the potential genetic basis of root anatomical plasticity during domestication.

Self-expanding transcatheter aortic valve replacement in patients with extremely horizontal aortas.

OBJECTIVES: To evaluate the feasibility of self-expanding transcatheter aortic valve replacement (TAVR) in patients with aortic stenosis and extremely horizontal aortas (aortic angulation ≥70°). BACKGROUND: As TAVR using a self-expanding prosthesis is an off-label treatment for patients with extremely horizontal aortas, these patients are often excluded from randomized controlled trials involving self-expanding TAVR. METHODS: This study enrolled 27 consecutive patients with extremely horizontal aortas who underwent self-expanding TAVR for severe aortic stenosis. RESULTS: The patients' average age was 76.4 years, with a median Society of Thoracic Surgeons score of 4.53%. The device success and 30-day mortality rates were 66.7% and 7.4%, respectively. The sinotubular junction (STJ) was significantly smaller in the device success group (p = 0.001). The receiver operating characteristic curve analysis found that the area under the curve was 0.907 (95% confidence interval: 0.790-1.000, p = 0.001), validating the association between STJ diameter and device success. An optimal cutoff of 33.6 mm was determined using the Youden index, with a sensitivity and specificity of 88.9% and 77.8%, respectively. The device success rate was significantly higher (93.3% vs. 33.3%, p = 0.003) in patients with STJ diameters ≤33.6 mm (n = 15). In the subgroup analyses, severe valve calcification (n = 9) was associated with a higher incidence of moderate or severe paravalvular leakage (44.0% vs. 0%, p = 0.008), while a higher rate of second valve implantation (60.0% vs. 9.1%, p = 0.030) was found in patients with less than moderate valve calcification (n = 5). CONCLUSION: Self-expanding TAVR could be suitable for patients with extremely horizontal aortas after careful preoperative evaluation.

Root and xylem anatomy varies with root length, root order, soil depth and environment in intermediate wheatgrass (Kernza®) and alfalfa.

BACKGROUND AND AIMS: Deep roots (i.e. >1 m depth) are important for crops to access water when the topsoil is dry. Root anatomy and hydraulic conductance play important roles in the uptake of soil water, particularly water located deep in the soil. We investigated whether root and xylem anatomy vary as a function of root type, order and length, or with soil depth in roots of two deep-rooted perennial crops: intermediate wheatgrass [Thinopyrum intermedium (Kernza®)] and alfalfa (Medicago sativa). We linked the expression of these anatomical traits to the plants' capacity to take up water from deep soil layers. METHODS: Using laser ablation tomography, we compared the roots of the two crops for cortical area, number and size of metaxylem vessels, and their estimated root axial hydraulic conductance (ERAHCe). The deepest roots investigated were located at soil depths of 2.25 and at 3.5 m in the field and in rhizoboxes, respectively. Anatomical differences were characterized along 1-m-long individual roots, among root types and orders, as well as between environmental conditions. KEY RESULTS: For both crops, a decrease in the number and diameter, or both, of metaxylem vessels along individual root segments and with soil depth in the field resulted in a decrease in ERAHCe. Alfalfa, with a greater number of metaxylem vessels per root throughout the soil profile and, on average, a 4-fold greater ERAHCe, took up more water from the deep soil layers than intermediate wheatgrass. Root anatomical traits were significantly different across root types, classes and growth conditions. CONCLUSIONS: Root anatomical traits are important tools for the selection of crops with enhanced exploitation of deep soil water. The development and breeding of perennial crops for improved subsoil exploitation will be aided by greater understanding of root phenotypes linked to deep root growth and activity.

Structural plasticity in roots of the hemiepiphyte Vanilla phaeantha Rchb.f. (Orchidaceae): a relationship between environment and function.

The aerial environment appears to structurally modify roots, which frequently show specializations for absorbing water and nutrients. Among those specializations are the velamen, a multiseriate epidermis generally composed of dead mature cells, and greater degrees of lignification in the endodermis, exodermis, and pith. Vanilla phaeantha is a hemiepiphyte used here as a model of study to determine which root characteristics demonstrate the most plasticity in response to aerial and terrestrial environments. It produces roots growing under three conditions: (1) aerial and free, growing from the highest branches towards the ground; (2) aerial roots attached to the phorophyte; and (3) terrestrial. Samples taken 3 cm from the apices were used to prepare histological slides. The tissues and other anatomical structures were measured and histochemically characterized. The most plastic characteristics were the external periclinal thicknesses of the exodermis and the total area occupied by the aerenchyma lacunae. The free roots were the longest, did not evidence root hairs, and had the largest number of the aerenchyma lacunae; they also evidenced greater thicknesses of the exodermis in contact with the epidermis walls that helped maintain their shapes. Terrestrial roots had root hairs around the entire circumference and intense infestations of mycorrhiza, indicating their involvement in nutrient acquisition. The adhering roots evidenced free regions similar to those of aerial roots, as well as adhering regions showed characteristics similar to terrestrial roots (with root hairs and mycorrhiza infestations).

Maize root responses to drought stress depend on root class and axial position.

In this study we tested the hypotheses that root classes would exhibit distinctive anatomical and architectural responses to drought stress, and that those responses would vary along the root axes. The root systems of four maize (Zea mays L.) sweet corn genotypes designated SC1, SC2, SC3 and SC4 were phenotyped under well-watered and drought treatments in greenhouse mesocosms, permitting increasing stratification of moisture availability as the drought progressed. Anatomical and architectural responses to drought were evaluated for each root class. Lignin distribution was assessed by image processing of UV-illuminated root cross-sections acquired by laser ablation tomography. The two cultivars with less biomass reduction under drought, SC3 and SC4, substantially enhanced lateral root development along the apical segments of axial roots when plants were grown with drought stress. These segments grew into the deeper part of the mesocosm where more moisture was available. Apical segments of the axial and large lateral roots from drought-stressed plants were thicker and had greater theoretical axial water conductance than basal segments, especially in SC3 and SC4. Basal segments of crown roots of SC3 and SC4 showed increased lignification of the stele under drought. Root anatomical and architectural responses to drought are complex and vary among cultivars and root classes, and along root axes. Drought-induced proliferation of lateral roots on apical segments of axial roots would be expected to enhance deep water acquisition, while lignification of axial roots could help preserve axial water transport.

A cut throat: a case of C5-C8 brachial plexus root transection providing evidence of T1 innervation of thumb and finger extensors.

The T1 nerve root is not routinely thought of as innervating the extensors of the thumb and fingers. Work by Bertelli and Ghizoni proposed that the pattern of brachial plexus paralysis with intact hand function and thumb and finger extensors traditionally attributed to C5/6/7 root injury is in fact a C5/6/7/8 injury, with only T1 remaining intact - a 'T1 hand'. This case presents a 19-year-old male who was stabbed in the neck; exploratory surgery determined complete transection of the brachial plexus, with only the T1 nerve root remaining intact. Clinical examination demonstrated grade M4 pronation (with pronator quadratus), wrist extension (with extensor carpi ulnaris), thumb and finger extension (with extensor policis longus and brevis, extensor digitorum communis and extensor index proprius), wrist flexion (with palmaris longus), finger flexion (with flexor digitorum superficialis and profundus), thumb flexion (with flexor policis longus), and thenar and hypothenar muscles. Extensor carpi radialis longus and brevis, flexor carpi radialis and flexor carpi ulnaris were paralyzed. Triceps scored M2. This case provides unequivocal evidence that the T1 root provides significant innervation to the extrinsic thumb and finger extensors.