Individual Root Research Articles

Do root modules still exist after they die?

BackgroundThe terminal branch orders of plant root systems are increasingly known as an ephemeral module. This concept is crucial to recognize belowground processes. However, it is unknown if root modules still exist after they die?MethodsThe decomposition patterns of the first five root orders were observed for 3 years using a branch-order classification, a litter-bag method and sequential sampling in a common subalpine tree species (Picea asperata) of southwestern China.ResultsTwo root modules were observed during the 3-year incubation. Among the first five branch orders, the first three order roots exhibited temporal patterns of mass loss, nutrients and stoichiometry distinct from their woody mother roots throughout the experimental period. This study, for the first time, reported the decomposition pattern of each individual root order and found a similar decomposition dynamic among ephemeral root branches in a forest tree species.ConclusionsResults from this study suggest that root modules may also exist after death, while more data are needed for confirmation. The findings may further advance our understanding of architecture-associated functional heterogeneity in the fine-root system and also improve our ability to predict belowground processes.

Field methods to study the spatial root density distribution of individual plants

The ecological study of root systems lags behind the understanding of the aboveground components of plant communities, mainly due to methodological challenges. As ecological root theory develops complexity, root investigation methods are required to meet higher standards of quantitative and detailed data. Spatial root density distribution of plants represents one of the main features pursued in ecological studies, as it provides insight into root foraging behavior and belowground competition. To study root density, ecologists should preferably use and develop methods with the potential to provide the most comprehensive information: Individual Root Density Distribution (IRDD), i.e. individual-level and spatially-explicit root density maps. Here, we review the existing methods to detect roots in the field (detection methods), and to infer the identity of these roots (identification methods). We discuss potential combinations of Detection and Identification (DI) methods, and the data quality that these combinations yield in respect to IRDD. We anticipate that root field ecologists progressively may want to adopt DI methods showing the highest potential to provide high-quality IRDD. These methods are (i) ground-penetrating radar or acoustic tomography in combination with tracking the roots to the individual plant (i.e. skeleton method sensu lato), (ii) soil sampling in combination with in situ root staining (for physiological individuals), or (iii) soil sampling in combination with DNA microsatellites or single nucleotide polymorphism sequencing (for genetic individuals).

Topographic Distribution of Carious Lesion on Young Permanent Mandibular Molars and Its Relation to Periapical Index Score of Apical Periodontitis: A Radiographic Analysis

INTRODUCTION: Caries in young permanent teeth progress rapidly resulting in early pulp involvement which further progresses into loss of mineralized tissue and severe periapical pathologies. The Periapical Index scoring system (PAI) proposed by Ørstavik et al. in 1986 is an invaluable diagnostic tool used to evaluate periapical lesion extent and severity by 2D digital intraoral periapical radiographic analysis with minimal radiation exposure and hence treatment planning.AIM: To evaluate the relationship of the surface distribution of caries in young permanent molars, pulpal involvement and periapical index (PAI) score with respect to individual root forming young permanent mandibular molars. MATERIALS AND METHOD: In this retrospective single-centre study, 100 pulpally involved carious young permanent mandibular molars were included, selected from the departmental records between August 2018-2019. Topographic distribution of caries and radiographic analysis (using PAI) was evaluated to see the effect of anatomical site of caries, individual anatomical form of root, and extent & severity of apical periodontitis developed.RESULT: No significant correlation between the site of caries involvement and PAI score was observed. PAI score for distal roots was higher(PAI> 2) as compared to mesial root for pulpally involved carious young permanent first molars (p-value mesial root-0.576 , distal root-0.591)CONCLUSION: PAI score is independent of the topographic distribution of caries and no correlation was observed. Periapical radiolucency does not depend on caries distribution, either it is mesial, distal or occlusal.

Development of a Radiographic Index for Periodontitis.

The use of radiographic indices is noticeably diminished due to the lack of simplicity and standardisation among the existing ones. The aim of this study was to introduce a radiographic index to aid clinicians in determining the extent and severity of interproximal alveolar bone loss (iABL), in relation to individual root lengths, among patients suffering from periodontitis. A retrospective analysis of 50 anonymised dental panoramic tomograms (DPTs) of patients with periodontitis was conducted. Visual interpretation of iABL was recorded by a single investigator and by 20 volunteering clinicians for the ‘worst site’ in each quintet. Results were compared to a gold standard quantification method. Intra-examiner and inter-examiner agreement were measured using the Kappa coefficient and the intra-class correlation coefficient, respectively. Validity was assessed using Cramér’s V test. The mean intra-examiner agreement on the severity and pattern of iABL was 0.808 (K) and 0.802 (K), respectively. A stronger overall inter-examiner agreement was noted when the severity in contrast to the pattern of iABL and presence/absence of furcation involvement were analysed. The statistically significant total mean agreement values from this correlation coefficient were 0.892 and 0.739, respectively. A very strong association between all the visual interpretations carried out by all participants and the gold standard measurements was evident. Within the limitations of this study, the proposed radiographic index may serve as a simple, yet valid and reliable, adjunctive screening tool to further assist clinicians in determining the extent and severity of iABL in patients with periodontitis.

Tissue-Autonomous Phenylpropanoid Production Is Essential for Establishment of Root Barriers

Plants deposit hydrophobic polymers, such as lignin or suberin, in their root cell walls to protect inner tissues and facilitate selective uptake of solutes. Insights into how individual root tissues contribute to polymer formation are important for elucidation of ultrastructure, function, and development of these protective barriers. Although the pathways responsible for production of the barrier constituents are established, our models lack spatiotemporal resolution-especially in roots-thus, the source of monomeric barrier components is not clear. This is mainly due to our restricted ability to manipulate synthesis of the broadly important phenylpropanoid pathway, as mutants in this pathway display lethal or pleiotropic phenotypes. Here, we overcome this challenge by exploiting highly controlled invivo repression systems. We provide strong evidence that autonomous production of phenylpropanoids is essential for establishment of the endodermal Casparian strip as well as adherence of the suberin matrix to the cell wall of endodermis and cork. Our work highlights that, in roots, the phenylpropanoid pathway is under tight spatiotemporal control and serves distinct roles in barrier formation across tissues and developmental zones. This becomes evident in the late endodermis, where repression of phenylpropanoid production leads to active removal of suberin in pre-suberized cells, indicating that endodermal suberin depositions might embody a steady state between continuous synthesis and degradation.

Inoculation with two Oidiodendron maius strains differentially alters the morphological characteristics of fibrous and pioneer roots of Vaccinium virgatum ‘Tifblue’ cuttings

Fine root systems of blueberries contain different individual fine roots suitable for absorptive or structural functions. However, there is limited information regarding how ericoid mycorrhizal fungi morphologically modify individual roots. Here, we focused on different individual roots that were classified into fibrous and pioneer roots based on whether their apical parts were smaller or larger than 100 μm in diameter. To develop root growth promoting techniques for cutting propagation of blueberries, we examined the hypothesis that inoculation with different Oidiodendron maius strains, EF1409 and EF1453, would alter the length and branching of pioneer and fibrous roots of the rabbiteye blueberry ‘Tifblue’ (Vaccinium virgatum) cuttings. Significant inoculation effects on individual root morphology were shown (P < 0.05); EF1409 significantly increased the length and branching of pioneer roots, whereas EF1453 moderately increased the branching of both root types, which supported our hypothesis. However, total root length and adventitious root number were not significantly affected by the different inoculations. There were positive correlations between total root length, adventitious root number, pioneer root length, and lateral root number of pioneer root. The best regression model suggested a dominant association between adventitious root number and total root length, although lateral root number of pioneer root was the second contributor to total root length. The differences in morphological alteration between the two strains suggested inter-strain or interspecific variation in function that modified morphology of different individual roots. Such variation is an important aspect for future techniques used to control the root systems of cuttings of blueberries and other ericaceous horticultural crops.

Long-term experimental warming and fertilization have opposing effects on ectomycorrhizal root enzyme activity and fungal community composition in Arctic tundra

As the Arctic rapidly warms, deciduous ectomycorrhizal (EcM) shrubs are expanding across the tundra. While we know how EcM host plants respond to warming and the associated nutrient release predicted for a future Arctic, considerably less is known about how EcM function will respond, despite their important role in plant nutrient acquisition in the nutrient-limited tundra. To explore how EcM-associated nutrient cycling may change, we characterized EcM-associated root enzyme activity and community in a 28-year full factorial warming and fertilization experiment in Arctic tundra. We measured activity at the individual root tip-level (pmol⋅min−1⋅mm−2 root) and used EcM root tip abundance to scale to community-level activity (pmol⋅min−1⋅cm−3 soil). We then Sanger sequenced fungi on the same root tips to pair identity with function. Linear mixed effects models and multivariate analysis showed warming and fertilization generally had opposing, and sometimes interacting, effects on EcM root-associated activity. Responses also differed depending on the scale. Fertilization decreased activity on both scales while warming dampened the effect of fertilization. Additionally, warming increased EcM root tip abundance, and therefore community-level enzyme activity. Ectomycorrhizal root tip communities changed with fertilization, but not with warming. Changes in enzyme activity were moderately correlated with both changes in fungal community and soil inorganic nitrogen concentrations. The contrast in responses of root tip-level activity and community-level activity point to a potential shift in allocation to EcM function: whereas the production of degradative enzymes may become less important for nutrient acquisition, the exploration of the soil environment through increased number of EcM root tips may become more important. Furthermore, the future role of EcM in a warmer Arctic likely depends on the magnitude of nutrient release that comes with warming. While warming may increase the importance of EcM-associated nutrient cycling if nutrient availability remains low, it has the potential to decrease their importance if nutrient availability greatly increases.

DNA-Metabarcoding of Belowground Fungal Communities in Bare-Root Forest Nurseries: Focus on Different Tree Species.

The production of tree seedlings in forest nurseries and their use in the replanting of clear-cut forest sites is a common practice in the temperate and boreal forests of Europe. Although conifers dominate on replanted sites, in recent years, deciduous tree species have received more attention due to their often-higher resilience to abiotic and biotic stress factors. The aim of the present study was to assess the belowground fungal communities of bare-root cultivated seedlings of Alnus glutinosa, Betula pendula, Pinus sylvestris, Picea abies and Quercus robur in order to gain a better understanding of the associated fungi and oomycetes, and their potential effects on the seedling performance in forest nurseries and after outplanting. The study sites were at the seven largest bare-root forest nurseries in Lithuania. The sampling included the roots and adjacent soil of 2–3 year old healthy-looking seedlings. Following the isolation of the DNA from the individual root and soil samples, these were amplified using ITS rRNA as a marker, and subjected to high-throughput PacBio sequencing. The results showed the presence of 161,302 high-quality sequences, representing 2003 fungal and oomycete taxa. The most common fungi were Malassezia restricta (6.7% of all of the high-quality sequences), Wilcoxina mikolae (5.0%), Pustularia sp. 3993_4 (4.6%), and Fusarium oxysporum (3.5%). The most common oomycetes were Pythium ultimum var. ultimum (0.6%), Pythium heterothallicum (0.3%), Pythium spiculum (0.3%), and Pythium sylvaticum (0.2%). The coniferous tree species (P. abies and P. sylvestris) generally showed a higher richness of fungal taxa and a rather distinct fungal community composition compared to the deciduous tree species (A. glutinosa, B. pendula, and Q. robur). The results demonstrated that the seedling roots and the rhizosphere soil in forest nurseries support a high richness of fungal taxa. The seedling roots were primarily inhabited by saprotrophic and mycorrhizal fungi, while fungal pathogens and oomycetes were less abundant, showing that the cultivation practices used in forest nurseries secured both the production of high-quality planting stock and disease control.

Modeling Root Exudate Accumulation Gradients to Estimate Net Exudation Rates by Peatland Soil Depth.

Root exudates accumulate as a radial gradient around the root, yet little is known about variability at the individual root level. Vertical gradients in soil properties are hypothesized to cause greater accumulation of exudates in deeper soil through hindering diffusion, increasing sorption, and decreasing mineralization. To this end, a single root exudation model coupling concentration specific exudation and depth dependent soil properties was developed. The model was parameterized for a peatland ecosystem to explore deposition to the methanogen community. Numerical experiments indicate that exudates accumulated to a greater extent in deeper soil, albeit the effect was solute specific. Rhizosphere size for glucose doubled between the 10 and 80 cm depths, while the rhizoplane concentration was 1.23 times higher. Root influx of glucose increased from 1.431 to 1.758 nmol cm−1 hr−1, representing a recapture efficiency gain of 15.74% (i.e., 69.06% versus 84.8%). Driven by increased root influx, overall net exudation rates of select sugars and amino acids varied by a factor two. Model sensitivity analysis revealed that soil depth and root influx capability are key determinants of the rhizoplane concentration and subsequently net exudation, which determines whether effluxed compounds escape the root oxic shell and are available to the methanogen community.

Importance of individual root traits to understand crop root system in agronomic and environmental contexts.

Resource acquisition, one of the major functions of roots, can contribute to crop growth and mitigating environmental impacts. The spatio-temporal distribution of roots in the soil in relation to the dynamics of the soil resources is critical in resource acquisition. Root distribution is determined by root system development. The root system consists of many individual roots of different types and ages. Each individual root has specific development, resource acquisition, and transport traits, which change with root growth. The integration of individual root traits in the root system could exhibit crop performance in the various environments via root distribution in the soil. However, the relationship between individual root traits and the pattern of root distribution is complicated. To understand this complicated relationship, we need to evaluate enormous numbers of individual root traits and understand the relationship between individual root development and root distribution as well as the integrated functions of individual root traits along with dynamics of resources in the soil.

金塔绿洲不同林龄多枝柽柳根系分叉数与分支角度的关系

PDF HTML阅读 XML下载 导出引用 引用提醒 金塔绿洲不同林龄多枝柽柳根系分叉数与分支角度的关系 DOI: 10.5846/stxb201907261581 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41861009，41461013） Relationship between root forks and branch angle of Tamarix ramosissima at different stand ages in oasis of Jinta County Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:根系构型影响根系空间分布和营养吸收效率，反映了植物适应环境胁迫的生存策略。采用标准化主轴估计（Standardized major axis estimation，SMA）的方法，分析了甘肃金塔北海子国家湿地公园3年生和6年生多枝柽柳（Tamarix ramosissima）根系分叉数与分支角度的异速生长关系。结果表明：随着林龄的增长，湿地群落盖度、高度逐渐增加，多枝柽柳种群的盖度、密度、高度和地上生物量以及根系深度、分叉数、比根长、比表面积、各级根系直径随之增加，根系分支角度和根冠比逐渐减小；多枝柽柳根系分叉数与分支角度回归方程的标准主轴斜率逐渐增大（P<0.05），随着林龄的增长，多枝柽柳根系分叉数的增加速度逐渐大于根系分支角度的生长速度，二者在林龄间呈现出差异化的异速生长关系。随着林龄的增长，多枝柽柳根系构型模式由"扩散型"转变为"紧缩型"，体现了种群应对生境胁迫和竞争的生态适应机制。 Abstract:The root architecture influences root spatial distribution and resorptiton efficiency of nutrients, which may reflect the plant growth strategies to adapt to the environmental stresses. This paper studied the relationship between root forks and branch angle of Tamarix ramosissim at three-year and six-year. The study site was located in Jinta Beihaizi Wetland Park of Gansu Province with the method of standardized major axis estimation (SMA). The height, density and above-ground biomass of the wetland communities were recorded from 5 m×5 m grids at two plots with six replicates. Seventy-two plants of Tamarix ramosissim were selected; the above-ground parts of those plants were cut while the roots were collected by excavating the whole root system, and both were taken back to the lab. In the laboratory, the roots were scanned with Win-RHIZO to measure the root forks and root length. The individual roots was dissected according to the branching order, starting from the distal end of the root system that was numbered as the first order and then increasing sequentially with each branch from the first order to the third order roots. The biomasses of different plots were put in an oven and dried (at 80℃ for 12 h), and then measured. Similarly, the soil moisture content was also measured by oven-drying (at 105 ℃for 24 h). The results showed that with the increasing stand ages, the density, cover, height of the plant community increased, while the root-shoot ratio, root branch angle decreased, the specific cover, density, height, above biomass, root depth, root forks, specific root length and specific root surface area increased, and diameter of different root orders increased. In addition, with the increasing stand ages, the standardized major axis slope of regression equation in the scaling relationships between root forks and branch angle increased (P<0.05). Additionally, the increase speed of the root forks was greater than the growth speed of the root branch angle, and the allometric relationship between root forks and branch angle of Tamarix ramosissima was distinguished at different stand ages. With the increasing stand ages, the root architecture model of Tamarix ramosissima form diffusion to gathering, reflected the mechanism of ecological adaptation under conditions of environmental stresses and competition of the population. 参考文献 相似文献 引证文献

The microbiomes on the roots of wheat (Triticum aestivum L.) and rice (Oryza sativa L.) exhibit significant differences in structure between root types and along root axes.

There is increasing interest in understanding how the microbial communities on roots can be manipulated to improve plant productivity. Root systems are not homogeneous organs but are comprised of different root types of various ages and anatomies that perform different functions. Relatively little is known about how this variation influences the distribution and abundance of microorganisms on roots and in the rhizosphere. Such information is important for understanding how root-microbe interactions might affect root function and prevent diseases. This study tested specific hypotheses related to the spatial variation of bacterial and fungal communities on wheat (Triticum aestivum L.) and rice (Oryza sativa L.) roots grown in contrasting soils. We demonstrate that microbial communities differed significantly between soil type, between host species, between root types, and with position along the root axes. The magnitude of variation between different root types and along individual roots was comparable with the variation detected between different plant species. We discuss the general patterns that emerged in this variation and identify bacterial and fungal taxa that were consistently more abundant on specific regions of the root system. We argue that these patterns should be measured more routinely so that localised root-microbe interactions can be better linked with root system design, plant health and performance.

A digital twin strategy for major failure detection in fused deposition modeling processes

Part distortion during additive manufacturing (AM) may lead to catastrophic failure and significant waste of resources. Existing work often focuses on identification and detection of individual root causes such as melt pool geometries or extruder clogging to prevent part failures. Since the end-effect of major print failures can be the result of multiple error sources (including unknowns), relying on detection of individual root causes may misclassify some failed prints as successful. Instead, detecting end-effects or part distortion could provide early warning of major failures regardless of potential error sources. Distortion detection, however, currently involves computationally expensive simulation and analysis of sensing data. One promising solution is to adopt digital twin strategy to quickly compare model prediction to features extracted from in situ sensing data. This study extends the digital twin strategy to major distortion detection by developing (1) a multi-view optical sensing system for movable print beds and (2) failure detection methods by analyzing multi-view of part images layer by layer. Since the digital twin of actual prints at specific layers are generated offline, delay can be reduced to determine if a significant enough quality departure has occurred to justify termination of the print. In the experimental evaluation of this approach for a FDM machine with a moving print bed, failure was rapidly detected in two of the three test prints, while in the remaining print, failure was successfully detected after a short delay.

Cbct analysis of apical distance between second lower premolars, first and second lower molars and mandibular canal

Introduction. Mandibular canal with the associated neurovascular bundle may be closely related to the apices of mandibular teeth. In order to avoid injuries and damages to the inferior alveolar nerve during invasive dental procedures, it is important to know its localization. The aim of this study was to determine the average vertical distances of the root apices of second premolars, first molars and second molars mesially and distally from the upper projection of the mandibular canal on the sagittal section of CBCT images, and determine if there were statistically significant differences between the age and gender groups. Material and methods. The research was conducted at the Faculty of Medicine of the University of Banja Luka, and the sample consisted of 146 CBCT images of patients. CBCT images were obtained using Planmeca ProMax 3D Mid instrument (Planmeca, Helsinki, Finland) and analyzed using Planmeca Romexis Viewer software. In the sagittal section, the vertical distance from the root apex to the upper projection of the mandibular canal was measured for each examined tooth. Results. The distal root of the first molar (4.88 mm) had the greatest average vertical distance of the root apex from the mandibular canal, and the distal root of the second molar had the smallest average vertical distance (2.76 mm). There was statistically significant difference between certain age groups in the values of individual roots, for the second molar mesially and distally (p &lt; 0.05), while for the first molar mesially the value of p was at the limit of significance (p = 0.05). Conclusion. The results of this study showed that distal root of the mandibular second molar had the smallest vertical distance from mandibular canal, therefore an extra caution during a root canal treatment and careful planning of oral surgery in this region is recommended.

Semiautomated 3D Root Segmentation and Evaluation Based on X-Ray CT Imagery.

Background Computed X-ray tomography (CTX) is a high-end nondestructive approach for the visual assessment of root architecture in soil. Nevertheless, in order to evaluate high-resolution CTX data of root architectures, manual segmentation of the depicted root systems from large-scale volume data is currently necessary, which is both time consuming and error prone. The duration of such a segmentation is of importance, especially for time-resolved growth analysis, where several instances of a plant need to be segmented and evaluated. Specifically, in our application, the contrast between soil and root data varies due to different growth stages and watering situations at the time of scanning. Additionally, the root system itself is expanding in length and in the diameter of individual roots. Objective For semiautomated and robust root system segmentation from CTX data, we propose the RootForce approach, which is an extension of Frangi's “multi-scale vesselness” method and integrates a 3D local variance. It allows a precise delineation of roots with diameters down to several μm in pots with varying diameters. Additionally, RootForce is not limited to the segmentation of small below-ground organs, but is also able to handle storage roots with a diameter larger than 40 voxels. Results Using CTX volume data of full-grown bean plants as well as time-resolved (3D + time) growth studies of cassava plants, RootForce produces similar (and much faster) results compared to manual segmentation of the regarded root architectures. Furthermore, RootForce enables the user to obtain traits not possible to be calculated before, such as total root volume (Vroot), total root length (Lroot), root volume over depth, root growth angles (θmin, θmean, and θmax), root surrounding soil density Dsoil, or form fraction F. Discussion. The proposed RootForce tool can provide a higher efficiency for the semiautomatic high-throughput assessment of the root architectures of different types of plants from large-scale CTX. Furthermore, for all datasets within a growth experiment, only a single set of parameters is needed. Thus, the proposed tool can be used for a wide range of growth experiments in the field of plant phenotyping.

Root vascular traits differ systematically between African savanna tree and grass species, with implications for water use.

Belowground functional traits play a significant role in determining plant water-use strategies and plant performance, but we lack data on root traits across communities, particularly in the tropical savanna biome, where vegetation dynamics are hypothesized to be strongly driven by tree-grass functional differences in water use. We grew seedlings of 21 tree and 18 grass species (N = 5 individuals per species) from the southern African savanna biome under greenhouse conditions and collected fine-root segments from plants for histological analysis. We identified and measured xylem vessels in 539 individual root cross sections. We then quantified six root vascular anatomy traits and tested them for phylogenetic signals and tree-grass differences in trait values associated with vessel size, number, and hydraulic conductivity. Grass roots had larger root xylem vessels than trees, a higher proportion of their root cross-sectional area comprised vessels, and they had higher estimated axial conductivities than trees, while trees had a higher number of vessels per root cross-sectional area than grasses did. We found evidence of associations between trait values and phylogenetic relatedness in most of these traits across tree species, but not grasses. Our findings support the hypothesis that grass roots have higher water transport capacity than tree roots in terms of maximum axial conductivity, consistent with the observation that grasses are more "aggressive" water users than trees under conditions of high soil moisture availability. Our study identifies root functional traits that may drive differential responses of trees and grasses to soil moisture availability.

Micropropagation in Moringa oleifera Lam for high-throughput Multiplication

Moringa oleifera is the most widely cultivated species of the Moringaceae family Attributed to several medicinal uses and a high nutritional value. An efficient in vitro clonal propagation methodology for Moringa oleifera (PKM1 Variety) was developed using nodal explants of young seedlings grown ex vitro. Nodes were cultured in Murashige and Skoog (MS) medium with different combinations of plant growth regulators. Multiple shoots were successfully achieved by culturing nodal explants in a medium containing different concentrations of 6-Benzylaminopurine (BAP) and Kinetin (Kin) in combination with naphthalene acetic acid (NAA). BAP at 2mgL-1was considered optimal for generating a maximum an average of 6.03±0.21 auxillary shoots per explants after 60 days of culture inoculation. A high rate of multiplication has been established by routine subculture on a similar shoot induction medium. Maximum numbers of individual roots were established on a medium containing indole-3-butyric acid (IBA) at 1.5mgL-1. Primary hardening was done in pots containing the potting mixture and transferred plantlets were covered with clear polythene bags. Seventy per-cent of the rooted plants survived and secondary hardening was carried out after 15 days in a shaded greenhouse.

Evidence for root adaptation to a spatially discontinuous water availability in the absence of external water potential gradients

We hereby show that root systems adapt to a spatially discontinuous pattern of water availability even when the gradients of water potential across them are vanishingly small. A paper microfluidic approach allowed us to expose the entire root system of Brassica rapa plants to a square array of water sources, separated by dry areas. Gradients in the concentration of water vapor across the root system were as small as 10-4⋅mM⋅m-1 (∼4 orders of magnitude smaller than in conventional hydrotropism assays). Despite such minuscule gradients (which greatly limit the possible influence of the well-understood gradient-driven hydrotropic response), our results show that 1) individual roots as well as the root system as a whole adapt to the pattern of water availability to maximize access to water, and that 2) this adaptation increases as water sources become more rare. These results suggest that either plant roots are more sensitive to water gradients than humanmade water sensors by 3-5 orders of magnitude, or they might have developed, like other organisms, mechanisms for water foraging that allow them to find water in the absence of an external gradient in water potential.

Sequential Application of Antioxidants Rectifies Ion Imbalance and Strengthens Antioxidant Systems in Salt-Stressed Cucumber.

Exogenous antioxidant applications enable salt-stressed plants to successfully cope with different environmental stresses. The objectives of this investigation were to study the effects of sequential treatments of proline (Pro), ascorbic acid (AsA), and/or glutathione (GSH) on 100 mM NaCl-stressed cucumber transplant’s physio-biochemical and growth traits as well as systems of antioxidant defense. Under salinity stress, different treatment of AsA, Pro, or/and GSH improved growth characteristics, stomatal conductance (gs), enhanced the activities of glutathione reductase (GR), superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT) as well as increased contents of AsA, Pro, and GSH. However, sequential application of antioxidants (GSH-Pro- AsA) significantly exceeded all individual applications, reducing leaf and root Cd2+ and Na+ contents in comparison to the control. In plants grown under NaCl-salt stress, growth characteristics, photosynthetic efficiency, membrane stability index (MSI), relative water content (RWC), contents of root and leaf K+ and Ca2+, and ratios of K+/Na+ and Ca2+/Na+ were notably reduced, while leaf contents of non-enzymatic and enzymatic antioxidants, as well as root and leaf Cd2+ and Na+ concentrations were remarkably increased. However, AsA, Pro, or/and GSH treatments significantly improved all investigated growth characteristics, photosynthetic efficiency, RWC and MSI, as well as AsA, Pro, and GSH, and enzymatic activity, leaf and root K+ and Ca2+ contents and their ratios to Na+, while significantly reduced leaf and root Cd2+ and Na+ contents.

Genetic variations of root development traits under different concentrations and forms of nitrogen in Bangladeshi rice (Oryza sativa L.) accessions

ABSTRACT Genetic variations in the root traits of rice remain unexplored in relation to varietal groups and diverse ecosystems. Therefore, we evaluated 257 Bangladeshi accessions, which included landraces and improved varieties belonging to four ecotypes (Aus, Aman, Boro and Jhum), to understand genetic variations in the total root length (TRL), maximum root length and root number under different concentrations of ammonium and nitrate nitrogen in hydroponic culture. There were large variations in all traits across all nitrogen levels. Active elongation of individual roots of the landrace type across all nitrogen conditions suggested a higher potential for the uptake of nutrients by extending roots distribution in any nitrogen environment, while the active development of primary root primordia in the improved type in the presence of nitrate suggested a higher potential for the uptake of nitrate from the soil surface by extending roots distribution around soil surface. Cluster analysis classified the examined accessions into two groups according to their TRL: cluster I with a longer TRL and cluster II with a shorter TRL across all nitrogen conditions. Each of these groups was further divided into two sub-clusters: sub-cluster Ia, in which the longer TRL resulted from active development of primary root primordia, sub-cluster Ib, in which the longer TRL resulted from active elongation of individual roots, sub-cluster IIa, in which the shorter TRL resulted from severe reduction of the elongation of individual roots, and sub-cluster IIb, in which the shorter TRL resulted from a moderate reduction in the elongation of individual roots. Further investigation revealed a difference in the composition of these four sub-clusters among the four ecotypes, indicating that Aman was the most diverse ecotype, followed by Aus. The root traits of these promising accessions could be exploited in the future to understand genetic and physiological mechanism(s) of adaptation to diverse ecosystems.