Multi-trait association mapping for phosphorous efficiency reveals flexible root architectures in sorghum.

BACKGROUND: On tropical regions, phosphorus (P) fixation onto aluminum and iron oxides in soil clays restricts P diffusion from the soil to the root surface, limiting crop yields. While increased root surface area favors P uptake under low-P availability, the relationship between the three-dimensional arrangement of the root system and P efficiency remains elusive. Here, we simultaneously assessed allelic effects of loci associated with a variety of root and P efficiency traits, in addition to grain yield under low-P availability, using multi-trait genome-wide association. We also set out to establish the relationship between root architectural traits assessed in hydroponics and in a low-P soil. Our goal was to better understand the influence of root morphology and architecture in sorghum performance under low-P availability. RESULT: In general, the same alleles of associated SNPs increased root and P efficiency traits including grain yield in a low-P soil. We found that sorghum P efficiency relies on pleiotropic loci affecting root traits, which enhance grain yield under low-P availability. Root systems with enhanced surface area stemming from lateral root proliferation mostly up to 40 cm soil depth are important for sorghum adaptation to low-P soils, indicating that differences in root morphology leading to enhanced P uptake occur exactly in the soil layer where P is found at the highest concentration. CONCLUSION: Integrated QTLs detected in different mapping populations now provide a comprehensive molecular genetic framework for P efficiency studies in sorghum. This indicated extensive conservation of P efficiency QTL across populations and emphasized the terminal portion of chromosome 3 as an important region for P efficiency in sorghum. Increases in root surface area via enhancement of lateral root development is a relevant trait for sorghum low-P soil adaptation, impacting the overall architecture of the sorghum root system. In turn, particularly concerning the critical trait for water and nutrient uptake, root surface area, root system development in deeper soil layers does not occur at the expense of shallow rooting, which may be a key reason leading to the distinctive sorghum adaptation to tropical soils with multiple abiotic stresses including low P availability and drought.

Sorghum hybrids grown in hydroponics contrast for phosphorus use efficiency / Híbridos de sorgo crescidos em hidroponia contrastam para eficiência de uso de fósforo

Phosphorus (P) use efficiency is crucial for sorghum production. P acquisition efficiency is the most important component of P use efficiency. The early-stage evaluation of plant development is a useful tool for identifying P-efficient genotypes. This study aimed to identify sorghum hybrids that are efficient in P use efficiency and assess the genetic diversity among hybrids based on traits related to P acquisition efficiency. Thus, 38 sorghum hybrids and two inbred lines (checks) were evaluated under low and high P in a paper pouch system with nutrient solution. Biomass and root traits related to P efficiency were measured. There was no interaction between genotypes and P levels concerning all evaluated traits. The biomass and root traits, except root diameter, presented smaller means under low P than high P. Efficient and inefficient hybrids under each P level were identified. The genetic diversity assessment grouped these genotypes in different clusters. The hybrids AG1090, MSK326, AG1060, 1G100, AS 4639, DKB 540, and DKB 590 were superior under low-P and high-P. Hybrids SC121, 1236020 e 1167017 presented the lowest means than all other hybrids, under both conditions. The evaluated hybrids showed phenotypic diversity for traits related to P acquisition, such as root length and root surface area, which can be useful for establishing selection strategies for sorghum breeding programs and increasing P use efficiency.

A eficiência do uso do fósforo (P) é fundamental para a produção de sorgo. A avaliação no estágio inicial do desenvolvimento da planta é uma ferramenta útil para a identificação de genótipos eficientes de P. Este trabalho teve como objetivo identificar híbridos de sorgo que sejam eficientes ao uso de P e avaliar a diversidade genética entre os híbridos com base em características relacionadas à eficiência de aquisição de P. Assim, 38 híbridos de sorgo e duas linhagens (testemunhas) foram avaliados sob baixo e alto P em sistema de pastas de papel com solução nutritiva. Características de biomassa e de raiz relacionadas à eficiência de P foram mensuradas. Não houve interação entre genótipos e níveis de P em todas as características avaliadas. As características de biomassa e raiz, exceto o diâmetro da raiz, apresentaram médias menores sob baixo P em comparação com alto P. Híbridos eficientes e ineficientes sob cada nível de P foram identificados e agrupados quanto à diversidade genética. Os híbridos AG1090, MSK326, AG1060, 1G100, AS 4639, DKB 540 e DKB 590 foram superiores sob baixo-P e alto-P. Os híbridos SC121, 1236020 e 1167017 apresentaram as menores médias que todos os outros híbridos, em ambas condições. Os híbridos avaliados apresentaram diversidade fenotípica para características relacionadas à aquisição de P, como comprimento e área superficial da raiz, o que pode ser útil para estabelecer estratégias de seleção para programas de melhoramento de sorgo e aumentar a eficiência de uso do P.

Sorghum hybrids grown in hydroponics contrast for phosphorus use efficiency

Abstract Phosphorus (P) use efficiency is crucial for sorghum production. P acquisition efficiency is the most important component of P use efficiency. The early-stage evaluation of plant development is a useful tool for identifying P-efficient genotypes. This study aimed to identify sorghum hybrids that are efficient in P use efficiency and assess the genetic diversity among hybrids based on traits related to P acquisition efficiency. Thus, 38 sorghum hybrids and two inbred lines (checks) were evaluated under low and high P in a paper pouch system with nutrient solution. Biomass and root traits related to P efficiency were measured. There was no interaction between genotypes and P levels concerning all evaluated traits. The biomass and root traits, except root diameter, presented smaller means under low P than high P. Efficient and inefficient hybrids under each P level were identified. The genetic diversity assessment grouped these genotypes in different clusters. The hybrids AG1090, MSK326, AG1060, 1G100, AS 4639, DKB 540, and DKB 590 were superior under low-P and high-P. Hybrids SC121, 1236020 e 1167017 presented the lowest means than all other hybrids, under both conditions. The evaluated hybrids showed phenotypic diversity for traits related to P acquisition, such as root length and root surface area, which can be useful for establishing selection strategies for sorghum breeding programs and increasing P use efficiency.

Resumo A eficiência do uso do fósforo (P) é fundamental para a produção de sorgo. A avaliação no estágio inicial do desenvolvimento da planta é uma ferramenta útil para a identificação de genótipos eficientes de P. Este trabalho teve como objetivo identificar híbridos de sorgo que sejam eficientes ao uso de P e avaliar a diversidade genética entre os híbridos com base em características relacionadas à eficiência de aquisição de P. Assim, 38 híbridos de sorgo e duas linhagens (testemunhas) foram avaliados sob baixo e alto P em sistema de pastas de papel com solução nutritiva. Características de biomassa e de raiz relacionadas à eficiência de P foram mensuradas. Não houve interação entre genótipos e níveis de P em todas as características avaliadas. As características de biomassa e raiz, exceto o diâmetro da raiz, apresentaram médias menores sob baixo P em comparação com alto P. Híbridos eficientes e ineficientes sob cada nível de P foram identificados e agrupados quanto à diversidade genética. Os híbridos AG1090, MSK326, AG1060, 1G100, AS 4639, DKB 540 e DKB 590 foram superiores sob baixo-P e alto-P. Os híbridos SC121, 1236020 e 1167017 apresentaram as menores médias que todos os outros híbridos, em ambas condições. Os híbridos avaliados apresentaram diversidade fenotípica para características relacionadas à aquisição de P, como comprimento e área superficial da raiz, o que pode ser útil para estabelecer estratégias de seleção para programas de melhoramento de sorgo e aumentar a eficiência de uso do P.

Analysis of the Internal and External Morphology of the Mandibular First Molar in a Chilean Sub-Population Using Cone-Beam Computed Tomography / Análisis de la Morfología Interna y Externa del Primer Molar Mandibular en una Subpoblación Chilena Mediante Tomografía Computarizada de Haz Cónico

SUMMARY: The mandibular first molar (MFM) commonly presents two roots with two canals in the mesial root and one or two canals in the distal root. However, morphological variations have been described in different populations, which must be considered when planning endodontic treatment. The aim of this study was to analyze the internal and external morphology of the MFM in a Chilean sub-population using cone-beam computed tomography (CBCT) images. An in vivo cross-sectional, descriptive, and observational study was conducted using CBCT exams from 351 right and left MFM. The data were analyzed by descriptive statistics using the Chi- Square test for categorical variables, Fisher's exact test, the Mann-Whitney U non-parametric test for two independent samples, and the Wilcoxon non-parametric test for related samples. Of the total sample, 1 root was observed in 2.27 % of the cases, 2 roots in 93.73 %, and 3 roots in 4 %. In relation to the number of canals, 71.23 % of the MFM showed 3 root canals, 16.81 % 4 canals, 9.69 % 2 canals, and 2.28 % 1 canal. Of all the studied cases, 2.3 % had a C-shaped anatomy. In terms of morphology, using Zhang's classification, variant 3 was observed in 71.23 %, variant 4 in 12.82 %, variant 1 in 9.67 %, variant 6 in 4 %, and variant 8 in 2.28 %. In conclusion, the morphology of the MFM is variable in a Chilean sub-population, and these variations must be considered before and during endodontic therapy. CBCT proved to be an effective tool for the in vivo study of tooth morphology.

El primer molar mandibular (MFM) comúnmente presenta dos raíces con dos canales en la raíz mesial y uno o dos canales en la raíz distal. Sin embargo, se han descrito variaciones morfológicas en distintas poblaciones, las que se deben tener en consideración al momento de planificar el tratamiento endodóntico. El objetivo de este estudio fue analizar la morfología interna y externa del MFM en una sub población chilena mediante el uso de imágenes de tomografía computarizada Cone Beam (CBCT). Se realizó un estudio transversal, descriptivo y observacional in vivo empleando exámenes CBCT de 351 MFM tanto derechos como izquierdos. Los datos se analizaron mediante estadística descriptiva empleando la prueba Chi-Cuadrado para variables categóricas, el test exacto de Fisher, la prueba no paramétrica de U-Mann-Whitney para dos muestras independientes y la prueba no paramétrica de Wilcoxon para muestras relacionadas. Del total de la muestra se observó 1 raíz en un 2.27 % de los casos, 2 raíces en 93.73 % y 3 raíces en un 4 %. En relación al número de canales un 71.23 % de los MFM mostraron 3 canales radiculares, un 16.81 % 4 canales, un 9.69 % 2 canales y un 2.28 % 1 canal. Del total de los casos estudiados un 2.3 % se presentó anatomía en forma de C. En relación a la morfología, empleando la clasificación de Zhang, se observó en un 71.23 % la variante tipo 3, en un 12.82 % la variante tipo 4, en un 9.67 % la variante tipo 1, en un 4 % variante tipo 6 y en un 2,28 % variante tipo 8. En conclusión, la morfología del MFM es variable en una subpoblación chilena y estas variaciones deben ser consideradas antes y durante la terapia endodóntica. El CBCT demostró ser una herramienta eficaz para el estudio in vivo de la morfología dentaria.

Estimation of root canal conicity of deciduous canines evaluated by nano-CT.

PURPOSE: To estimate the taper of root canals of deciduous maxillary and mandibular canines by nano computed tomography (nano-CT). METHODS: This in vitro study involved CT scan analysis of nine maxillary and five mandibular primary canines. The images of each tooth were reconstructed using OnDemand3D software. Thereon, diameter and taper analyses were performed on the free FreeCAD 0.18 software for the three-dimensional (3D) computer-aided design model. Statistical analysis was conducted using Stata v14.0 software, adopting a significance level of 5%. RESULTS: 3D image reconstruction was performed, considering the diameters obtained along the entire length of the tooth root, and the conical model was built with a height of 10 mm. The diameters of the maxillary canine at points D0 (0 mm), D5 (5 mm), D7 (7 mm), and D10 (10 mm) were 1.62, 1.07, 0.78, and 0.49 mm, respectively, with a significant difference between the four points (p = 0.0001). Regarding maxillary canine root taper values in the cervical, middle, and apical regions, the values were 12%, 14%, and 10%, respectively. For mandibular canines, the mean diameter values obtained at points D0, D5, D7, and D10 were 1.51, 0.83, 0.64, and 0.45 mm, respectively, with significant differences among the four points (p = 0.005). The inferior canine root tapers in the cervical, middle, and apical regions were 14%, 10%, and 6%, respectively. CONCLUSION: The detailed knowledge of the root morphology of maxillary and mandibular deciduous canines, as it has been shown in vitro using nano-CT, is critical to achieve accurate and efficient endodontic treatments.

Genome-Wide Association Study for Root Morphology and Phosphorus Acquisition Efficiency in Diverse Maize Panels.

Maximizing soil exploration through modifications of the root system is a strategy for plants to overcome phosphorus (P) deficiency. Genome-wide association with 561 tropical maize inbred lines from Embrapa and DTMA panels was undertaken for root morphology and P acquisition traits under low- and high-P concentrations, with 353,540 SNPs. P supply modified root morphology traits, biomass and P content in the global maize panel, but root length and root surface area changed differentially in Embrapa and DTMA panels. This suggests that different root plasticity mechanisms exist for maize adaptation to low-P conditions. A total of 87 SNPs were associated to phenotypic traits in both P conditions at -log10(p-value) ≥ 5, whereas only seven SNPs reached the Bonferroni significance. Among these SNPs, S9_137746077, which is located upstream of the gene GRMZM2G378852 that encodes a MAPKKK protein kinase, was significantly associated with total seedling dry weight, with the same allele increasing root length and root surface area under P deficiency. The C allele of S8_88600375, mapped within GRMZM2G044531 that encodes an AGC kinase, significantly enhanced root length under low P, positively affecting root surface area and seedling weight. The broad genetic diversity evaluated in this panel suggests that candidate genes and favorable alleles could be exploited to improve P efficiency in maize breeding programs of Africa and Latin America.

Has the literature thoroughly categorized the lower third molars? A new classification of the various lower third molar root forms for a better understanding of their morphology / ¿La literatura ha categorizado minuciosamente los terceros molares inferiores? Una nueva clasificación de las diversas formas radiculares del tercer molar inferior para una mejor comprensión de su morfología

SUMMARY: Impacted lower third molars (IL3M) have different root shapes and numbers. This study aimed to create a classification for IL3M root forms, that should aid in understanding roots morphology. A retrospective cross-sectional study on patients had IL3M at the university clinics between 2017 and 2019. Panoramic radiographs were retrieved to classify the roots into fused roots (FR): one or two roots connected from furcation to apices, and separated roots (SR): two or more roots not connected from furcation to apical third, and each type has different forms. Statistical analysis was done by Chi-Square test. Five-hundred patients, males (54.6 %) and females (45.4 %) were included. SR were in 591 teeth (75.5 %), and FR in 192 teeth (24.5 %). Statistically significant associations emerged between SR and males (60 %) and between FR and females (66 %) (p = .000). SR forms were straight (45.8 %), joined roots (28.2 %), one straight and one curved (13.3 %), roots curved distal (9.1 %), roots curved mesial (2.5 %), and more than two roots (0.3 %). FR forms were straight (87.5 %), curved distal (9.4 %), S-shaped (2.1 %), and curved mesial (1 %). The common angulations of IL3M with SR were vertical (39 %) followed by mesioangular (25.7 %), while FR were mostly vertical (39.1 %) or horizontal (23.9 %). The classification is applicable on panoramic radiographs, and complements Winter and Pell & Gregory to provide a better description of IL3M status by adding root morphology to the angulation, occlusal, and ramus relationship.

Los terceros molares inferiores impactados (3MII) tienen diferentes formas y números de raíces. Este estudio tuvo como objetivo crear una clasificación para las formas de raíz 3MII, que debería ayudar a comprender la morfología de las raíces. Realizamos un estudio transversal retrospectivo de pacientes con 3MII en las clínicas universitarias entre 2017 y 2019. Se recuperaron radiografías panorámicas para clasificar las raíces en raíces fusionadas (RF): una o dos raíces conectadas desde la zona de furca a los ápices y raíces separadas (RS): dos o más raíces no conectadas desde la bifurcación al tercio apical, y cada tipo con formas diferentes. El análisis estadístico se realizó mediante la prueba Chi-Cuadrado. Se incluyeron 500 pacientes, hombres (54,6 %) y mujeres (45,4 %). RS se observó en 591 dientes (75,5 %) y RF en 192 dientes (24,5 %). Surgieron asociaciones estadísticamente significativas entre RS y hombres (60 %) y entre RF y mujeres (66 %) (p = .000). Las formas de RS eran rectas (45,8 %), raíces unidas (28,2 %), una recta y una curva (13,3 %), raíces curvas distales (9,1 %), raíces curvas mesiales (2,5 %) y más de dos raíces (0,3 %).). Las formas RF eran rectas (87,5 %), curvas distales (9,4 %), en forma de S (2,1 %) y curvas mesiales (1 %). Las angulaciones comunes de 3MII con RS fueron verticales (39 %), seguidas de mesioangular (25,7 %), mientras que RF fueron mayoritariamente verticales (39,1 %) u horizontales (23,9 %). La clasificación es aplicable en radiografías panorámicas y complementa a Winter y Pell & Gregory para proporcionar una mejor descripción del estado de 3MII al agregar la morfología de la raíz a la relación de angulación, oclusal y rama.

Tolerance of cultivars and clonal selections of peach rootstocks to excess aluminum / Tolerância de cultivares e seleções clonais de porta-enxertos de pessegueiro ao excesso de alumínio

Forms of aluminum (Al) present in the solution of tropical and subtropical soils can cause toxicity in rootstocks and peach cultivars, impairing growth and productivity. This can be minimized by growing Al-tolerant rootstocks and cultivars. However, this is not sufficiently known, especially because plant breeding programs do not always consider tolerance as a selection variable for genetic materials. The study aimed to (a) select cultivars and clonal selections of Al-tolerant peach rootstocks, (b) identify variables that confer Al tolerance for use in genetic improvement programs, and (c) propose critical levels (NC) and ranges of toxicity (TF) of Al in relation to morphological variables of the root system. The experimental design was completely randomized, comprising a factorial of 13 (cultivars and clonal selections) x 2 (with and without Al) with three replications. Own-rooted 'BRS Mandinho' peach seedlings (without rootstock) and grafted seedlings of 'BRS Mandinho' on different cultivars and clonal rootstock selections were cultivated in a hydroponic system, composing two levels for the Al factor (absence and presence at 100 mg L−1). The morphological variables of the canopy and root system, Al accumulation in tissues, translocation factor, and the critical level (NC) and toxicity range (TF) of Al in the roots were evaluated. Rootstocks FB-SM-09-43, JB-ESM-09-13, SAS-SAU-09-71, SS-CHI-09-40, 'Sharpe' and VEH-GRA-09-55 were tolerant at high Al concentrations. The NC of Al in the roots in relation to the root surface area of peach rootstocks was 1400 mg Al kg−1, and the FT was between 1200 and 1500 mg Al kg−1.(AU)

Formas de alumínio (Al) presentes na solução de solos tropicais e subtropicais podem causar toxicidade em porta-enxertos e cultivares de pessegueiro, prejudicando o crescimento e a produtividade. Isso pode ser minimizado pelo cultivo de porta-enxertos e cultivares tolerantes ao Al. Porém, isso não é suficientemente conhecido, principalmente porque os programas de melhoramento vegetal nem sempre consideram a tolerância como uma variável de seleção de materiais genéticos. O estudo teve como objetivo (a) selecionar cultivares e seleções clonais de porta-enxertos de pessegueiro tolerantes ao Al, (b) identificar variáveis que confiram tolerância ao Al para uso em programas de melhoramento genético e (c) propor níveis críticos (NC) e faixas de toxicidade (FT) do Al em relação às variáveis morfológicas do sistema radicular. O delineamento experimental foi inteiramente casualizado, compreendendo fatorial 13 (cultivares e seleções clonais) x 2 (com e sem Al) com três repetições. Mudas de pessegueiro 'BRS Mandinho' autoenraizadas (sem porta-enxerto) e mudas enxertadas de 'BRS Mandinho' em diferentes cultivares e seleções de porta-enxertos clonais foram cultivadas em sistema hidropônico, compondo dois níveis para o fator Al (ausência e presença a 100 mg L−1). Foram avaliadas as variáveis morfológicas da parte aérea e do sistema radicular, acúmulo de Al nos tecidos, fator de translocação, NC e FT do Al nas raízes. Os porta-enxertos FB-SM-09-43, JB-ESM-09-13, SAS-SAU-09-71, SS-CHI-09-40, 'Sharpe' e VEH-GRA-09-55 foram tolerantes a altas concentrações de Al. O NC do Al nas raízes em relação à área radicular dos porta-enxertos de pessegueiro foi de 1400 mg Al kg−1, e o FT ficou entre 1200 e 1500 mg Al kg−1.(AU)

Root system structure as a criterion for the selection of grapevine genotypes that are tolerant to excess copper and the ability of phosphorus to mitigate toxicity.

Using tolerant genotypes and the correct use of fertilizers can mitigate the negative effect of elevated Cu levels in the growing medium. In this context, the study aimed to evaluate the effects of excess Cu in the root system and the effectiveness of phosphorus (P) in minimizing the phytotoxicity of Cu in three genotypes: IAC 572 [(Vitis riparia x V. rupestris) x V. caribaea], Magnolia (V. rotundifolia) and Paulsen 1103 (V. berlandieri x V. rupestris). The plants were grown in nutrient solutions and were supplemented with the following treatments: 0.3 µM Cu (Control), 60 µM Cu (Cu) and 60 µM Cu and 62 mg L-1 P (Cu + P). Root samples were sectioned for microscopy analyses, and the shoot lengths, shoot and root dry matter, relative growth rates (RGR) and tissue nutrient contents were also evaluated. The roots of the genotypes that were cultivated with high Cu concentrations produced greater numbers of branches and larger diameters, except for Magnolia genotype that was cultivated in a Cu + P solution, which had an organization similar to the control. Excess Cu caused accumulations of phenolic compounds and decreased shoot lengths, dry matter and RGR in the genotypes. In the treatments with excess Cu, there were increases in this element in the tissues, but P decreased the metal concentrations in Magnolia roots. Therefore, Cu accumulations alter the root system development patterns, growth parameters and tissue nutrient contents in the studied genotypes. Magnolia has a higher tolerance and is also the only genotype for which the use of P has been shown to be effective.

Machine learning applied to the prediction of root architecture of soybean cultivars under two water availability conditions / Machine learning aplicado à predição da arquitetura radicular de cultivares de soja sob duas condições de disponibilidade hídrica

The objective of this study was to evaluate the performance of four machine learning models, as well as multitask learning, to predict soybean root variables from simpler variables, under two water availability conditions. In order to do so, 100 soybean cultivars were conducted in a greenhouse under a control condition and a stress condition. Aerial part and root variables were evaluated. The machine learning models used to predict complex root variables were artificial neural network (ANN), random forest (RF), extreme gradient boosting (EGBoost) and support vector machine (SVM). A linear model was used for comparison purposes. Multitask learning was employed for ANN and RF. In addition, feature importance was defined using RF and XGBoost algorithms. All the machine learning models performed better than the linear model. In general, SVM had the greatest potential for the prediction of most of the root variables, with better values of RMSE, MAE and R2. Dry weight of the aerial part and root volume exhibited the greatest importance in the predictions. The models developed using multitask learning performed similarly to the ones conventionally developed. Finally, it is concluded that the machine learning models evaluated can be used to predict root variables of soybean from easily measurable variables, such as dry weight of the aerial part and root volume.(AU)

O objetivo deste estudo foi avaliar o desempenho de quatro modelos de machine learning, bem como multitask learning, para predizer variáveis radiculares de soja a partir de variáveis simples, em duas condições de disponibilidade hídrica. Para isso,100 cultivares de soja foram conduzidas em casa de vegetação sob uma condição controle e uma condição estresse. Foram avaliadas as variáveis da parte aérea e da raiz. Os modelos machine learning usados para predizer variáveis complexas do sistema radicular foram rede neural artificial (RNA), random forest (RF), extreme gradient boosting (EGBoost) e support vector machine (SVM). O modelo linear foi usado para fins de comparação. O multitask learning foi empregado para RNA e RF. Além disso, a importância das variáveis foi definida usando algoritmos RF e XGBoost. Todos os modelos de machine learning apresentaram melhor desempenho do que o modelo linear. Em geral, SVM apresentou o maior potencial de predição da maioria das variáveis raiz, com melhores valores de RMSE, MAE e R2. O peso seco da parte aérea e o volume da raiz exibiram as maiores importâncias nas predições. Os modelos desenvolvidos por meio do multitask learning apresentaram desempenhos semelhantes aos desenvolvidos convencionalmente. Por fim, conclui-se que os modelos de machine learning avaliados podem ser usados para predizer variáveis radiculares de soja a partir de variáveis facilmente mensuráveis, como massa seca da parte aérea e volume radicular.(AU)

Root and root canal system morphology of maxillary first premolars in a Chilean subpopulation: a cone-beam Computed Tomography Study / Morfología radicular y del sistema de canales radiculares de los primeros premolares maxilares en una subpoblación chilena: un estudio de tomografía computarizada de haz de cono

SUMMARY: The maxillary first premolar (MFP) presents a highly variable and complex root morphology; it is also one of the teeth most likely to suffer vertical root fractures. The aim of this study was to describe the morphology of the root and root canal system of the MFP in a Chilean population using Cone-Beam Computed Tomography (CBCT). One hundred and twenty-one MFP were evaluated (60 left and 61 right), belonging to subjects of both sexes. Descriptive and statiscal analysis of the data was carried out, with a value of P < 0.05 being statistically significant. One root was observed in 71 % of teeth and two roots in 29 %; statistically significant differences were observed in the number of roots by sex (p<0.05). Two root canals were found in 69.5 % of teeth and one canal in 30.5 %. In terms of morphological classification, 41.3 % of cases were Vertucci Type IV. The proximal cementodentinal walls were the thinnest. The MFP presented a high degree of morphological variation in a Chilean subpopulation.

RESUMEN: El primer premolar maxilar (PPM) presenta una morfología radicular muy variable y compleja; también es uno de los dientes con mayor probabilidad de sufrir fracturas radiculares verticales. El objetivo de este estudio fue describir la morfología de la raíz y el sistema de conductos radiculares del PPM en una población chilena mediante tomografía computarizada de haz cónico (CBCT). Se evaluaron 121 PPM (60 izquierdas y 61 derechas), pertenecientes a sujetos de ambos sexos. Se realizó un análisis descriptivo y estadístico de los datos, siendo estadísticamente significativo un valor de P < 0,05. Se observó una raíz en el 71 % de los dientes y dos raíces en el 29 %; se observaron diferencias estadísticamente significativas en el número de raíces por sexo (p<0.05). Se encontraron dos conductos radiculares en el 69,5 % de los dientes y un conducto en el 30,5 %. En cuanto a la clasificación morfológica, el 41,3 % de los casos fueron Vertucci Tipo IV. Las paredes cementodentinales proximales fueron las más delgadas. El PPM presentó un alto grado de variación morfológica en una subpoblación chilena.

The variation in crown-root morphology of anterior teeth assessed with cone-beam computed tomography

ABSTRACT Objective: To determine the discrepancy of crown-root morphology of anterior teeth, using cone-beam computed tomography (CBCT), and to provide a guidance for proper torque expression. Methods: A total of eligible 200 CBCT were imported into Invivo v. 5.4 software, to obtain the middle labio-lingual sections of anterior teeth. AutoCAD 2007 software was applied to measure the crown-root angulation (Collum angle) and the angle formed by a tangent to the center of the labial surface and the long axis of the crown (labial surface angle). SPSS 18.0 was used for statistical comparisons of the two measurements, at the level of p< 0.05, and the Pearson correlation analysis was applied to investigate the association between the two measurements. Results: The value of Collum angle in maxillary central incisor was close to 0°. Significantly negative Collum angle in lateral incisors and maxillary canine, and positive value in mandibular canine were detected (p < 0.001). The labial surface angle in canine was significantly greater than the intra-arch incisors (p< 0.001), and no significant difference was detected between the central and lateral incisors (p > 0.05). Notably, there was also a significant positive correlation between the two measurements. Conclusions: The crown-root angulations were greatly different among anterior teeth. Accompanying the obvious crown-root angulations, the canines both in maxillary and mandibular arches presented considerable labial surface curvatures. Hence, equivalent deviation during bracket bonding might cause greater torque expression error and increase the risk of alveolar fenestration and dehiscence.

RESUMO Objetivo: Determinar a discrepância na morfologia coroa-raiz de dentes anteriores, utilizando tomografia computadorizada de feixe cônico (TCFC), e fornecer parâmetros para a expressão apropriada do torque. Método: No total, 200 tomografias elegíveis foram importadas para o software Invivo 5.4 para obtenção das secções médias vestibulolinguais dos dentes anteriores. Osoftware AutoCAD 2007 foi usado para medir a angulação coroa-raiz (ângulo Collum) e o ângulo formado por uma tangente ao centro da superfície vestibular da coroa e o longo eixo da coroa (ângulo da superfície vestibular). O software SPSS 18.0 foi utilizado para as comparações estatísticas das duas medições, com nível de significância de p< 0,05, e a análise de correlação de Pearson foi aplicada para investigar a associação entre as duas medições. Resultados: O valor do ângulo Collum do incisivo central superior foi próximo a 0°. Foram detectados valores significativamente negativos para o ângulo Collum nos incisivos laterais e caninos superiores, mas valores positivos nos caninos inferiores (p< 0,001). O ângulo da superfície vestibular no canino foi significativamente maior do que nos incisivos intra-arcada (p< 0,001), e nenhuma diferença significativa foi detectada entre incisivos centrais e laterais (p> 0,05). Também foi observada uma correlação positiva significativa entre as duas medições. Conclusões: As angulações coroa-raiz foram muito diferentes entre os dentes anteriores. Os caninos superiores e inferiores apresentaram considerável curvatura na superfície vestibular, associada a uma evidente angulação coroa-raiz. Consequentemente, desvios durante a colagem de braquetes podem desencadear maior erro na expressão de torque e aumentar o risco de fenestração alveolar e deiscência, sendo necessária uma avaliação antes da colagem.

The Steroid Saponin Protodioscin Modulates Arabidopsis thaliana Root Morphology Altering Auxin Homeostasis, Transport and Distribution.

To date, synthetic herbicides are the main tools used for weed control, with consequent damage to both the environment and human health. In this respect, searching for new natural molecules and understanding their mode of action could represent an alternative strategy or support to traditional management methods for sustainable agriculture. Protodioscin is a natural molecule belonging to the class of steroid saponins, mainly produced by monocotyledons. In the present paper, protodioscin's phytotoxic potential was assessed to identify its target and the potential mode of action in the model plant Arabidopsis thaliana. The results highlighted that the root system was the main target of protodioscin, which caused a high inhibitory effect on the primary root length (ED50 50 µM) with morphological alteration, accompanied by a significant increase in the lateral root number and root hair density. Through a pharmacological and microscopic approach, it was underlined that this saponin modified both auxin distribution and transport, causing an auxin accumulation in the region of root maturation and an alteration of proteins responsible for the auxin efflux (PIN2). In conclusion, the saponin protodioscin can modulate the root system of A. thaliana by interfering with the auxin transport (PAT).

Rapid responses of root traits and productivity to phosphorus and cation additions in a tropical lowland forest in Amazonia.

Soil nutrient availability can strongly affect root traits. In tropical forests, phosphorus (P) is often considered the main limiting nutrient for plants. However, support for the P paradigm is limited, and N and cations might also control tropical forests functioning. We used a large-scale experiment to determine how the factorial addition of nitrogen (N), P and cations affected root productivity and traits related to nutrient acquisition strategies (morphological traits, phosphatase activity, arbuscular mycorrhizal colonisation and nutrient contents) in a primary rainforest growing on low-fertility soils in Central Amazonia after 1 yr of fertilisation. Multiple root traits and productivity were affected. Phosphorus additions increased annual root productivity and root diameter, but decreased root phosphatase activity. Cation additions increased root productivity at certain times of year, also increasing root diameter and mycorrhizal colonisation. P and cation additions increased their element concentrations in root tissues. No responses were detected with N addition. Here we showed that rock-derived nutrients determined root functioning in low-fertility Amazonian soils, demonstrating not only the hypothesised importance of P, but also highlighting the role of cations. The changes in fine root traits and productivity indicated that even slow-growing tropical rainforests can respond rapidly to changes in resource availability.

Primer premolar inferior con dos conductos y doble trayecto fistuloso: caso clínico / First lower premolar with two canals and double fistulous path: a clinical case

El tratamiento endodóntico del primer premolar inferior, cuando presenta varios conductos o varias raíces puede ser un gran desafío. En el presente trabajo se describe un caso clínico de un paciente de sexo masculino de 60 años de edad que concurre al Servicio de Guardia de la Facultad de Odontología de la Universidad de Buenos Aires (FOUBA). Al examen clínico y radiográfico se descubre la presencia de dos trayectos fistulosos que corresponden a la misma pieza dentaria con diagnóstico de absceso alveolar crónico. Concluimos que el operador debe realizar un minucioso diagnóstico, y analizar y conocer las diferentes configuraciones anatómicas para tratarlas adecuadamente, aumentando así las probabilidades de éxito del tratamiento (AU)

Endodontic treatment of the first lower premolar when it has multiple ducts or multiple roots can be a challenge. This paper describes a clinical case of a 60-year-old male patient who attends the on-call service of the School of Dentistry of the University of Buenos Aires (FOUBA). Upon clinical and radiographic examination, the presence of two sinusal tracts that corresponded to the same dental piece with a diagnosis of chronic alveolar abscess was discovered. We conclude that the operator must carry out a thorough diagnosis and analyze and understand the different anatomical configurations in order to properly treat them, thus increasing the probability of treatment success (AU)

Vermicompost improves maize, millet and sorghum growth in iron mine tailings.

The Fundão dam was designed to store iron mine tailings in the region of Mariana, MG, Brazil. When it ruptured, the tailings overflowed. These tailings affected the soil due to the formation of a thick crust as a result of drying (compaction) and hindered the natural revegetation process. In this context, the use of organic fertilizers, including vermicompost, is method of reducing the physical limitations on root growth caused by soil properties and changing soil-metal interactions. For this reason, vermicompost was added to iron mine tailings, and its morphological and physiological effects on maize, millet and sorghum plants were studied. The experiment was conducted in a greenhouse using 6 dm3 pots. The plants were subjected to three treatments: mine tailings, mine tailings + vermicompost, and a reference soil. From the V3 stage onwards, biweekly growth, leaf gas exchange and chlorophyll fluorescence evaluations were performed. At the end of the experiment, dry biomass and metal, macro- and micronutrient contents were quantified, and the root morphology was evaluated. The tailings created physical limitations on root growth and had low nutrient content as well as high concentrations of chromium, iron and manganese. The addition of vermicompost favored increases in shoot and root dry biomass, increases in root length, volume, surface area and diameter, and the absorption of macro- and micronutrients, which was reflected in the growth of the studied species. In addition, vermicompost led to greater investment in thick and very thick roots, and in general, the plants showed no symptoms of metal toxicity. Considering the characteristics of the studied tailings, it can be concluded that vermicompost favors the growth of plant species and may be a viable method for beginning the recovery process in areas containing iron mine tailings.

Establishment and optimization of a hydroponic system for root morphological and nutritional analysis of citrus

The hydroponic growth system is a convenient platform for studying whole plant physiology, especially for root morphological and nutritional analysis. However, we found that most hydroponic systems described in the literature are not suitable for citrus plants. In this study, a hydroponic system for citrus was designed, comprising three principal components: power and time switch, aeration and hydroponic culture. Herein, details of the protocol were described, including equipment setup, seed pregermination and cultivation, together with preparation and transfer of nutrient solution into hydroponics. In order to demonstrate the adaptability of the trifoliate orange plant to our hydroponic system, comparative tests between soil- and hydroponically-grown plants were carried out. The results showed that the plants grew normally and there were no obvious differences between soil- and hydroponically-grown plants. In addition, nutrient deficiency and transcriptional analysis were carried out to test the efficiency, functionality and suitability of our hydroponic system for the application of physiological and molecular analysis. The results, compared with previous studies, showed that our hydroponic system delivered superior performance as regards the physiological and molecular analysis. Taken together, we established the culture system which is best suited for the growth of trifoliate oranges under hydroponic conditions. The hydroponic system described in this paper is easily constructed and controlled at a low cost. It may serve a wide gamut of experimental purposes, especially root morphological and nutritional analysis of trifoliate oranges and the system is also adaptable to other citrus plants by varying the device size.(AU)

Establishment and optimization of a hydroponic system for root morphological and nutritional analysis of citrus

The hydroponic growth system is a convenient platform for studying whole plant physiology, especially for root morphological and nutritional analysis. However, we found that most hydroponic systems described in the literature are not suitable for citrus plants. In this study, a hydroponic system for citrus was designed, comprising three principal components: power and time switch, aeration and hydroponic culture. Herein, details of the protocol were described, including equipment setup, seed pregermination and cultivation, together with preparation and transfer of nutrient solution into hydroponics. In order to demonstrate the adaptability of the trifoliate orange plant to our hydroponic system, comparative tests between soil- and hydroponically-grown plants were carried out. The results showed that the plants grew normally and there were no obvious differences between soil- and hydroponically-grown plants. In addition, nutrient deficiency and transcriptional analysis were carried out to test the efficiency, functionality and suitability of our hydroponic system for the application of physiological and molecular analysis. The results, compared with previous studies, showed that our hydroponic system delivered superior performance as regards the physiological and molecular analysis. Taken together, we established the culture system which is best suited for the growth of trifoliate oranges under hydroponic conditions. The hydroponic system described in this paper is easily constructed and controlled at a low cost. It may serve a wide gamut of experimental purposes, especially root morphological and nutritional analysis of trifoliate oranges and the system is also adaptable to other citrus plants by varying the device size.

Natural Root Cellular Variation in Responses to Osmotic Stress in Arabidopsis thaliana Accessions.

Arabidopsis naturally occurring populations have allowed for the identification of considerable genetic variation remodeled by adaptation to different environments and stress conditions. Water is a key resource that limits plant growth, and its availability is initially sensed by root tissues. The root's ability to adjust its physiology and morphology under water deficit makes this organ a useful model to understand how plants respond to water stress. Here, we used hyperosmotic shock stress treatments in different Arabidopsis accessions to analyze the root cell morphological responses. We found that osmotic stress conditions reduced root growth and root apical meristem (RAM) size, promoting premature cell differentiation without affecting the stem cell niche morphology. This phenotype was accompanied by a cluster of small epidermal and cortex cells with radial expansion and root hairs at the transition to the elongation zone. We also found this radial expansion with root hairs when plants are grown under hypoosmotic conditions. Finally, root growth was less affected by osmotic stress in the Sg-2 accession followed by Ws, Cvi-0, and Col-0; however, after a strong osmotic stress, Sg-2 and Cvi-0 were the most resilience accessions. The sensitivity differences among these accessions were not explained by stress-related gene expression. This work provides new cellular insights on the Arabidopsis root phenotypic variability and plasticity to osmotic stress.

Iron and callose homeostatic regulation in rice roots under low phosphorus.

BACKGROUND: Phosphorus (Pi) deficiency induces root morphological remodeling in plants. The primary root length of rice increased under Pi deficiency stress; however, the underlying mechanism is not well understood. In this study, transcriptome analysis (RNA-seq) and Real-time quantitative PCR (qRT-PCR) techniques were combined with the determination of physiological and biochemical indexes to research the regulation mechanisms of iron (Fe) accumulation and callose deposition in rice roots, to illuminate the relationship between Fe accumulation and primary root growth under Pi deficient conditions. RESULTS: Induced expression of LPR1 genes was observed under low Pi, which also caused Fe accumulation, resulting in iron plaque formation on the root surface in rice; however, in contrast to Arabidopsis, low Pi promoted primary root lengthening in rice. This might be due to Fe accumulation and callose deposition being still appropriately regulated under low Pi. The down-regulated expression of Fe-uptake-related key genes (including IRT, NAS, NAAT, YSLs, OsNRAMP1, ZIPs, ARF, and Rabs) inhibited iron uptake pathways I, II, and III in rice roots under low Pi conditions. In contrast, due to the up-regulated expression of the VITs gene, Fe was increasingly stored in both root vacuoles and cell walls. Furthermore, due to induced expression and increased activity of ß-1-3 glucanase, callose deposition was more controlled in low Pi treated rice roots. In addition, low Pi and low Fe treatment still caused primary root lengthening. CONCLUSIONS: The obtained results indicate that Low phosphorus induces iron and callose homeostatic regulation in rice roots. Because of the Fe homeostatic regulation, Fe plays a small role in rice root morphological remodeling under low Pi.