Spore studies in the genus Gymnocarpium

1983 ◽  
Vol 61 (2) ◽  
pp. 377-388 ◽  
Author(s):  
Kathleen M. Pryer ◽  
D. M. Britton
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
North America ◽  
Ploidy Level ◽  
Species Discrimination ◽  
Scanning Electron Micrographs ◽  
Positive Identification ◽  
Distinctive Morphology ◽  
Diploid Taxon ◽  
Scanning Electron

Scanning electron microscopy was used to examine the variation in perispore characters within and between six currently recognized taxa of the genus Gymnocarpium Newm. in North America. Representative scanning electron micrographs are presented and depict the perispore features observed. Spores of those taxa studied here do not each possess a distinctive morphology providing practical species discrimination, rather they all exhibit similar patterns of variation. Spore size was also examined and shown to be correlated to ploidy level, permitting positive identification of the diploid taxon G. dryopteris ssp. disjunctum from the tetraploid G. dryopteris ssp. dryopteris.

Elemental Analysis of Alkalis and Dental Deposits Associated with Coca Chewing in Ecuador

2006 ◽  
Vol 17 (1) ◽  
pp. 77-89 ◽  
Author(s):  
Douglas H. Ubelaker ◽  
Karen E. Stothert
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Spectral Analysis ◽  
North America ◽  
Elemental Analysis ◽  
X Ray ◽  
Tooth Structure ◽  
Elemental Analyses ◽  
The Relationship ◽  
Scanning Electron

AbstractThe relationship between Andean coca use and dental deposits is explored through the use of scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS). Elemental analyses of samples of large dental deposits from archeologically recovered skeletons from Ecuador dating between 500 B.C. and A.D. 1532 are compared with those of normal calculus deposits of individuals from North America (modern and precontact), of normal tooth structure and of samples of alkali recovered from Ecuadorian artifacts thought to have been employed in coca use. Spectral analysis revealed homogeneity among all dental samples (deposits and structure) and that they are distinct from the elemental pattern revealed in the analysis of the artifact alkalis.

Alternative Method of Rapid Drying Vascular Specimens for Scanning Electron Microscopy

2003 ◽  
Vol 10 (2) ◽  
pp. 285-287 ◽  
Author(s):  
DáŠa Slížová ◽  
Otakar Krs ◽  
Blanka PospíŠilová
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Electron Micrographs ◽  
Low Cost ◽  
High Rate ◽  
Drying Methods ◽  
Scanning Electron Micrographs ◽  
Air Drying ◽  
Critical Point Drying ◽  
Scanning Electron

Purpose: To report the use of hexamethyldisilazane (HMDS) as an alternative to critical point drying for preparing stented canine peripheral vessels for scanning electron microscopy (SEM). Technique: Vascular specimens were fixed in 4% formaldehyde overnight, dehydrated in a graded ethanol series, followed by immersion in 100% hexamethyldisilazane. After air drying, the specimens were mounted on stainless steel stubs, coated with gold, and examined in the SEM. The electron micrographs were of high quality, showing the layers of the vascular wall and the incorporated stent covered by a neointimal layer. The micrographs were comparable to corresponding histological sections, but detailed endothelial patterns were more visible. Conclusions: HMDS treatment and subsequent air drying provides good quality scanning electron micrographs that reveal both endothelial patterns and the layered architecture of stented vessels. The disadvantage of HMDS drying may be a shrinkage and distortion similar to other drying agents. Ease of handling, low cost, and a high rate of success are advantages that favor HMDS desiccation over other drying methods.

scholarly journals Molecular phylogeny and morphologic data of strains of the genus Coelastrella (Chlorophyta, Scenedesmaceae) from a tropical region in North America (Yucatan Peninsula)

2017 ◽  
Vol 95 (3) ◽  
pp. 527 ◽  
Author(s):  
Katia Ancona-Canché ◽  
Silvia López-Adrián ◽  
Margarita Espinosa-Aguilar ◽  
Gloria Garduño-Solórzano ◽  
Tanit Toledano-Thompson ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Phenotypic Plasticity ◽  
North America ◽  
Yucatan Peninsula ◽  
Tropical Region ◽  
Its2 Rdna ◽  
Yucatán Peninsula ◽  
Good Support ◽  
Scanning Electron

<p><strong>Background: </strong>Scenedesmaceae family exhibits great morphological variability. High phenotypic plasticity and the presence of cryptic species have resulted in taxonomic re-assignments of Scenedesmaceae members.</p><p><strong>Study strains: </strong><strong>S</strong>trains CORE-1, CORE-2 and CORE-3 were characterized.</p><p><strong>Study site: </strong>Yucatan Peninsula</p><p><strong>Methods: </strong><strong>Morphological analyses were executed by optical and scanning electron microscopy. P</strong>hylogenetic relationships were examined by ITS-2 and ITS1-5.8S-ITS2 rDNA regions.<strong></strong></p><p><strong>Results:</strong> Optical and scanning electron microscopy analyses indicated spherical to ellipsoidal cells and autospore formation correspond to members of the family Scenedesmaceae, as well as observable pyrenoid starch plates. Detailed morphology analysis indicated that CORE-1 had visible granulations dispersed on the cell wall, suggesting identity with <em>Verrucodesmus verrucosus</em>. However CORE-1 did not show genetic relations with this species, and was instead clustered close to the genus <em>Coelastrella</em>. CORE-2 did not show any particular structure or ornamentation, but it did show genetic relations with <em>Coelastrella</em> with good support. CORE-3 showed meridional ribs from end to end, one of them forked and well pronounced, and orange cells in older cultures characteristic of <em>Coelastrella</em> specimens. Phylogenetic trees of ITS-2 and ITS1-5.8S-ITS2 rDNA sequences indicated with good support that all strains were related to the genus <em>Coelastrella</em> despite their morphologic differences.</p><p><strong>Conclusions: </strong>This study reports freshwater <em>Coelastrella</em> strains from a tropical region in North America (Yucatan Peninsula) for the first time. The results contribute to knowledge of <em>Coelastrella</em> species, and the fact that they do not always show structures that are useful for taxonomic assignment, probably as a result of phenotypic plasticity.</p>

Delicate Botanical Specimens Preserved for Scanning Electron Microscopy by Critical Point Drying

1971 ◽  
Vol 29 ◽  
pp. 450-451
Author(s):  
Arthur L. Cohen ◽  
Gerald E. Garner
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Critical Point ◽  
Freeze Drying ◽  
Animal Cell ◽  
Pollen Grains ◽  
Scanning Electron Micrographs ◽  
Animal Cells ◽  
Critical Point Drying ◽  
Scanning Electron

The surface forms and structures of animal cells have been strikingly preserved for scanning electron microscopy by freeze-drying and by critical point drying both by the method with CO2 used as the transitional fluid and the later procedure which uses a fluorocarbon (Freon 13) as a medium for the transition from the liquid to the gaseous environment. Freeze-drying is often prolonged (5-12 hours as compared with an hour or less by the critical point method) and in our experience with mold cultures on agar, the substrate shrivels and cracks and hyphal filaments are distorted.Despite, and possibly because of a flexible but inelastic cell wall, plant cells often show greater distortion than do animal cells after evaporative drying or replacement dehydration for mixrotechnical work. The animal cell membrane can contract more or less uniformly on drying - as shown by the numerous micrographs of well-preserved erythrocytes, while plant cell walls often crumple. The many scanning electron micrographs of partially collapsed pollen grains bear witness to this fact.

Quantitative Scanning Electron Microscopy of the Cellular Structure of Wood

1990 ◽  
Vol 48 (1) ◽  
pp. 554-555
Author(s):  
Barbara A. Reine ◽  
Norman J. Fowler ◽  
R. M. Fisher
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Shear Strength ◽  
Cellular Structure ◽  
Cell Structure ◽  
Cork Oak ◽  
Scanning Electron Micrographs ◽  
Quantitative Interpretation ◽  
Structural Components ◽  
Scanning Electron

The physical properties of wood, such as density, moisture content, tensile, compression and shear strength, elastic modulus and anisotropy all vary considerably between different species of wood. These variations are reflected in the long standing differentiations into hard and soft woods that have been established as well as quality classifications or commercial grades such as clear grain, select, structural etc. that are commonly used. These variations in properties arise from differences in the size, shape and distribution of the cells, as well as in the thickness of the cellulose-lignin walls that enclose them.Scanning electron micrographs that are representative of the variations in cellular structure that exist between woods are shown in Figure 1 for ultrasoft hard maple and ultrasoft cork oak. These higher magnification images illustrate the duplex cell configuration that is required to sustain the growth of trees and support their height. Although the differences in cell structure are quite apparent in the micrographs, any quantitative interpretation of the various properties mentioned above requires detailed measurements of specific microstructural components to obtain statistically significant measurements of the relevant structural components.

scholarly journals The species of Mentzelia (Loasaceae) in Mexico, part 2: Mentzelia section Bartonia

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
John Schenk ◽  
Carolina Granados Mendoza ◽  
Andres Eduardo Estrada-Castillón
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Species Diversity ◽  
North America ◽  
Species Identification ◽  
Seed Coat ◽  
Western North America ◽  
Distribution Ranges ◽  
Scanning Electron ◽  
Study Species

Background: Mentzelia (Loasaceae) is primarily distributed in western North America. The genus is classified into six monophyletic sections, among which species of section Bartonia are particularly poorly understood. Questions: What species of Mentzelia section Bartonia occur in Mexico? What are the species distribution ranges and what are their defining attributes? Study species: Mentzelia section Bartonia. Methods: Field, herbarium, distribution, and scanning electron microscopy studies were conducted to assess species diversity. Seed coat microsculpture patterns were evaluated to confirm species identities and understand their distributions throughout Mexico. Results: Six species from section Bartonia were recognized, with taxa distributed into either the Chihuahuan or Sonoran deserts. Mentzelia longiloba var. pinacatensis is the only Mexican endemic. Conclusions: Although this work comprehensively addressed the species of section Bartonia in Mexico, two groups will continue to present identification challenges: the M. longiloba and M. mexicana-M. saxicola complexes. Overlapping and variable characters will continue to complicate species identification in the M. longiloba complex, while the late-season loss of primary leaves will obscure species identification between M. mexicana and M. saxicola.

Gomphosinica selincuoensis sp. nov., a new diatom (Bacillariophyceae) from North Tibet, China

Phytotaxa ◽  
2019 ◽  
Vol 423 (3) ◽  
pp. 195-205 ◽  
Author(s):  
LI YANG ◽  
QING-MIN YOU ◽  
J. P. KOCIOLEK ◽  
LI-QING WANG ◽  
WEI ZHANG
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
New Species ◽  
North America ◽  
The Other ◽  
Central Portion ◽  
Similar Species ◽  
A New Species ◽  
Scanning Electron

A new species, Gomphosinica selincuoensis sp. nov., is described from Lake Selincuo, North Tibet, China. This taxon is clearly different from the other species in genus Gomphosinica, with a distinctly protracted, rostrate headpole, relatively higher striae density, and distinctive areolae arrangement within the striae. Striae have areolae mostly in 3 rows, but there are places near the central portion of the valve and at footpole where there are only 2 rows of areolae per stria. Characteristics of this taxon, as observed in light and scanning electron microscopy, support its systematic placement in the genus Gomphosinica. This new species is compared with similar species in Gomphosinica from China and North America, and the biogeographic distribution of the genus is discussed.

scholarly journals Description of the egg of Anopheles (Anopheles) intermedius (Peryassu, 1908) (Diptera: Culicidae) by scanning electron microscopy

1997 ◽  
Vol 39 (1) ◽  
pp. 5-10 ◽  
Author(s):  
Oswaldo Paulo Forattini ◽  
Maria Anice Mureb Sallum ◽  
Daniel C. Flores
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Electron Micrographs ◽  
Scanning Electron Micrographs ◽  
Scanning Electron

The egg of Anopheles (Anopheles) intermedius (Peryassu, 1908) is described and illustrated with scanning electron micrographs. Literature data on An. (Ano.) maculipes (Theobald, 1903) is provided

Isoetes ×echtuckerii, hyb. nov., a new triploid quillwort from northeastern North America

2000 ◽  
Vol 77 (11) ◽  
pp. 1662-1668 ◽  
Author(s):  
Daniel F Brunton ◽  
Donald M Britton
Keyword(s):  
Electron Microscopy ◽  
United States ◽  
Scanning Electron Microscopy ◽  
North America ◽  
United States Of America ◽  
Interspecific Hybrid ◽  
Eastern Canada ◽  
Northeastern North America ◽  
Spore Ornamentation ◽  
Scanning Electron

A new interspecific Isoetes hybrid, I. echinospora Dur. × I. tuckermanii A. Br., is described from northeastern North America by means of cytology and the scanning electron microscopy of spores. Isoetes ×echtuckerii D.F. Brunton and D.M. Britton, hyb. nov., is the name proposed for this taxon. It is triploid, produces only aborted, sterile spores and has spore ornamentation intermediate between that of its putative parents. Populations have been identified in eastern Canada and the adjacent United States of America growing in association with one or both parents in shallow, fresh water along oligotrophic lake and river shores. Key words: Isoetes ×echtuckerii, interspecific hybrid, Canada, United States of America.

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