Distance and Direction of Retained Root Migration After Lower Third Molar Coronectomy

Background: The present study evaluated the pattern of root migration following coronectomy of the mandibular third molar in terms of distance, degree of direction, and relevant factors related to root migration. Methods: This retrospective study included 50 coronectomies in 44 patients with at least 1-year follow-up. Panoramic radiographs were taken pre-operatively, within 2 weeks after surgery, and at 3, 6, and 12 months post-operatively. Multiple factors are possibly related to root migration, so we analyzed sex, age, tooth, figure of root, residual bone height, and also as Winter’s and Pell& Gregory classification with respect to angulation, class, and position of tooth. Results: Over the first three months after the coronectomies, all retained roots moved and/or changed their root axis. The respective mean distance of retained root migration in the horizontal (C1), coronal (C2), and oblique (C3) direction during the first year post-operatively was 3.14 ± 1.86 mm, 2.42 ± 1.61 mm, and 3.45 ±1.76 mm. The mean (±SD) root axis change was 11.26 ± 5.55 degrees. The significant influencing factors related to root migration were sex, age, and in particular tooth angulation (GEE: P<0.05). The mesio- and horizontal angulation (M, H) group migrated significantly further horizontally forward (C1) over time than the vertical (V) and distoangulation (D) group. The V, D group showed significantly greater coronal migration (C2) (P=0.05) than the M, H group. The V, D group had only mesial rotation. Conclusion: These findings could contribute to evaluation and/or planning for root removal.

Somatic Embryogenesis and Plant Regeneration in Viola canescens Wall. Ex. Roxb.: An Endangered Himalayan Herb

Viola canescens Wall. ex. Roxb. is an important but threatened medicinal herb found at 1500–2400 m above mean sea level in the Himalayas. Overexploitation and habitat preference have put the plant under serious threat. Thus, the present study was undertaken to develop an efficient protocol for in vitro propagation via somatic embryogenesis. The results revealed that plant can be regenerated successfully through somatic embryogenesis using leaf derived calli. Regular subculturing of calli on Murashige and Skoog (MS) medium with 2,4-dichlorophenoxyacetic acid (2,4-D)/indole-3-butyric acid (IBA)/kinetin (Kn) and varying combinations of 2,4-D+Kn induced somatic embryogenesis. The maximum average number of somatic embryos (SE) (19.15 ± 2.66) was induced on the medium with 0.15 + 0.05 mg L−1 of 2,4-D and Kn, respectively, and this medium was used as a control. To enhance somatic embryo induction, the control MS medium was supplemented with l-glutamine (200–400 mg L−1) and casein hydrolysate (1–4%). The maximum average number of SE (27.66 ± 2.67) and average mature SE (13.16 ± 3.48) were recorded on the medium having 2 % l-glutamine and 50 mg L−1 casein hydrolysate. The induced SE were asynchronous, so, to foster their maturation, the culture medium (free from growth regulators) was supplemented with abscisic acid (ABA) and silver nitrate (AgNO3). The maximum average number (35.96 ± 3.68) of mature SE was noticed on MS medium supplemented with 1.5 mg L−1 ABA. Mature embryos had two well-developed cotyledons and an elongated hypocotyl root axis. The development of SE into plantlets was significant for embryos matured on the medium with AgNO3 and ABA, with 86.67% and 83.33% conversion on the medium with 0.20 mg L−1 6-benzylaminopurine (BAP). The plantlets thus produced acclimatized in a growth chamber before being transferred to the field, which showed 89.89% survival. The plants were morphologically similar to the mother plant with successful flowering.

Spatiotemporal Dynamics of Maize (Zea mays L.) Root Growth and Its Potential Consequences for the Assembly of the Rhizosphere Microbiota

Numerous studies have shown that plants selectively recruit microbes from the soil to establish a complex, yet stable and quite predictable microbial community on their roots – their “microbiome.” Microbiome assembly is considered as a key process in the self-organization of root systems. A fundamental question for understanding plant-microbe relationships is where a predictable microbiome is formed along the root axis and through which microbial dynamics the stable formation of a microbiome is challenged. Using maize as a model species for which numerous data on dynamic root traits are available, this mini-review aims to give an integrative overview on the dynamic nature of root growth and its consequences for microbiome assembly based on theoretical considerations from microbial community ecology.

Assembly patterns of the rhizosphere microbiome along the longitudinal root axis of maize (Zea mays L.)

&lt;p&gt;This study was conducted within the framework of the DFG project SPP2089 &amp;#8220;Rhizosphere Spatiotemporal Organization &amp;#8211; a Key to Rhizosphere Functions&amp;#8221;.&lt;/p&gt;&lt;p&gt;Different plant species select for individual subsets of bulk soil microbial communities within root systems. The fast variability of root environments implies that roots constitute highly dynamic habitats. Rapid root elongation, combined with widely varying quality and quantity of rhizodeposition between different root regions, lead to continuously changing conditions for colonizing microorganisms. As the microbiome concept implies a rather static outcome of the microbial assembly, it raises the question as to where and how the dynamic transition of a microbial bulk soil community into a plant species-specific rhizosphere microbiome is taking place.&lt;/p&gt;&lt;p&gt;To investigate the assembly of communities of prokaryotes and their microbial predators (Cercozoa, Rhizaria; protists) along the longitudinal root axis of maize (Zea mays L.), plants were grown in an agricultural loamy soil. Rhizosphere soil was sampled at distinct locations along roots. Diversity and co-occurrence of rhizosphere microbiota along the root axis were tracked by high-throughput sequencing, diversity measures and network analyses.&lt;/p&gt;&lt;p&gt;High variation in beta diversity at root tips and the root hair zone indicated substantial randomness of community assembly. Deterministic processes of community assembly were revealed by low variability of beta diversity, changes in network topology, and the appearance of regular phylogenetic co-occurrence patterns in bipartite networks between prokaryotes and their microbial predators. Deterministic processes were most robust in regions with fully developed lateral roots, suggesting that a consistent rhizosphere microbiome finally assembled. For the targeted improvement of microbiome function, such knowledge on the processes of microbiome assembly on roots and its temporal and spatial variability is of crucial importance.&lt;/p&gt;

Assembly Patterns of the Rhizosphere Microbiome Along the Longitudinal Root Axis of Maize (Zea mays L.)

It is by now well proven that different plant species within their specific root systems select for distinct subsets of microbiota from bulk soil – their individual rhizosphere microbiomes. In maize, root growth advances several centimeters each day, with the locations, quality and quantity of rhizodeposition changing. We investigated the assembly of communities of prokaryotes (archaea and bacteria) and their protistan predators (Cercozoa, Rhizaria) along the longitudinal root axis of maize (Zea mays L.). We grew maize plants in an agricultural loamy soil and sampled rhizosphere soil at distinct locations along maize roots. We applied high-throughput sequencing, followed by diversity and network analyses in order to track changes in relative abundances, diversity and co-occurrence of rhizosphere microbiota along the root axis. Apart from a reduction of operational taxonomic unit (OTU) richness and a strong shift in community composition between bulk soil and root tips, patterns of microbial community assembly along maize-roots were more complex than expected. High variation in beta diversity at root tips and the root hair zone indicated substantial randomness of community assembly. Root hair zone communities were characterized by massive co-occurrence of microbial taxa, likely fueled by abundant resource supply from rhizodeposition. Further up the root where lateral roots emerged processes of community assembly appeared to be more deterministic (e.g., through competition and predation). This shift toward significance of deterministic processes was revealed by low variability of beta diversity, changes in network topology, and the appearance of regular phylogenetic co-occurrence patterns in bipartite networks between prokaryotes and their potential protistan predators. Such patterns were strongest in regions with fully developed laterals, suggesting that a consistent rhizosphere microbiome finally assembled. For the targeted improvement of microbiome function, such knowledge on the processes of microbiome assembly on roots and its temporal and spatial variability is crucially important.

Root age influences failure location in grass species during mechanical testing

Aims Root tensile tests are often rejected if failure location is outside the middle section of samples. This study aims to identify where and why failure occurs along a root axis, and hence to revisit current approaches to test-validity. Methods Roots from Festuca arundinacea; Lolium multiflorum; Lolium perenne were sampled from field-grown plants. Roots were tensile tested using a universal testing machine. Root samples were randomly allocated into two groups for testing. Group 1 roots were orientated with the older tissue closest to the top clamp, group 2 roots were orientated oppositely. Tensile strength, Young’s modulus and failure location were recorded for each sample. Results Lolium multiflorum roots were thinner and stronger than roots of Festuca arundinacea. Failure location in tensile tests depended significantly on tissue age with 75% of samples failing in the younger third of root tissue regardless of the root orientation in the testing frame. Only 7% of roots failed in the middle third of the sample. Conclusions Fibrous roots tested in tension were observed to consistently fail in the younger tissue along the root axis. Exclusion of samples which fail outside the middle region of the root axis needs re-evaluation for a range of species.

Local brassinosteroid biosynthesis enables optimal root growth

Brassinosteroid hormones are indispensable for root growth and they control both cell division and cell elongation through the establishment of an increasing signaling gradient along the longitudinal root axis. Because of their limited mobility, the importance of brassinosteroid distribution for achieving the signaling maximum is largely overlooked. Expression pattern analysis of all known brassinosteroid biosynthetic enzymes revealed that not all cells in the Arabidopsis thaliana root possess full biosynthetic machinery and completion of biosynthesis relies on cell-to-cell movement of the hormone precursors. We demonstrate that brassinosteroid biosynthesis is largely restricted to the root elongation zone where it overlaps with brassinosteroid signaling maxima. Moreover, optimal root growth requires hormone concentrations, low in the meristem and high in the root elongation zone attributable to an increased biosynthesis. Our finding that spatiotemporal regulation of hormone synthesis results in a local hormone accumulation provides a paradigm for hormone-driven organ growth in the absence of long-distance hormone transport in plants.

Germination under High Temperatures of Maize Adapted to the Cerrado of Tocantins

The purpose of this study was to evaluate the response of germination and vigor in maize seeds in laboratory conditions, exposure to high temperatures, in order to highlight the most adaptable genotypes at these temperatures. Were supplied three cultivars of the PIONEIRA LTDA. (PIONEIRA HS-9, PIONEIRA HS-14i, PIONEIRA ROBUSTO), to perform the experiment, in addition to the commercial cultivar BRS 3040. After the selection of superior genotypes, were performed at temperatures of 25 reviews, 30, 35 and 40ºC, these being: germination, first count, seedling dry mass and speed index of the emergence of seedlings. At the temperature of 25°C were made the cold test and seedling length, shoot and root axis. The results were submitted to analysis of variance, comparison of averages by Tukey test, to three genotypes and regression analysis to high school, to three genotypes and the witness commercial. Whereas the maximum temperature of 35°C tested, one could observe that the PIONEIRA HS-6 genotype presented the best adaptation to high temperatures. The PIONEIRA ROBUSTO genotype was more adapted to high temperatures whereas as the highest temperature of 40°C. The BRS 3040 was not adapted to the high temperatures in relation to genotypes produced under conditions of high temperatures of the Cerrado.

Root hair-endophyte stacking (RHESt) in an ancient Afro-Indian crop creates an unusual physico-chemical barrier to trap pathogen(s)

The ancient African crop, finger millet, has broad resistance to pathogens including the toxigenic fungusFusarium graminearum. Here we report the discovery of a novel plant defence mechanism, resulting from an unusual symbiosis between finger millet and a root-inhabiting bacterial endophyte, M6 (Enterobactersp.). Seed-coated M6 swarms towardsFusariumattempting to penetrate root epidermis, induces growth of root hairs which then bend parallel to the root axis, then forms biofilm-mediated microcolonies, resulting in a remarkable, multi-layer root hair-endophyte stack (RHESt). RHESt results in a physical barrier that prevents entry and/or trapsF. graminearumwhich is then killed. Thus M6 creates its own specialized killing microhabitat. M6 killing requires c-di-GMP-dependent signalling, diverse fungicides and xenobiotic resistance. Further molecular evidence suggests long-term host-endophyte-pathogen co-evolution. The end-result of this remarkable symbiosis is reduced DON mycotoxin, potentially benefiting millions of subsistence farmers and livestock. RHESt demonstrates the value of exploring ancient, orphan crop microbiomes.