Pollen morphology of some Tamarix (Tamaricaceae) species of Iran

2020 ◽  
Vol 62 (1-2) ◽  
pp. 151-161
Author(s):  
T. Shagholi ◽  
M. Keshavarzi ◽  
M. Sheidai
Keyword(s):  
North Africa ◽  
Pollen Grains ◽  
Ecological Niches ◽  
Multivariate Statistical Methods ◽  
Multivariate Statistical ◽  
Qualitative And Quantitative ◽  
Petal Length ◽  
Electron Microscopes ◽  
High Level ◽  
Scanning Electron Microscopes

Tamarix L. (Tamaricaceae) is a halophytic shrub in different parts of Asia and North Africa. Taxonomy and species limitation of Tamarix is very complex. This genus has three sections as Tamarix, Oligadenia, and Polyadenia, which are mainly separated by petal length, the number of stamens, the shape of androecial disk and attachment of filament on the androecial disk. As there was no palynological data on pollen features of Tamarix species of Iran, in the present study 12 qualitative and quantitative pollen features were evaluated to find diagnostic ones. Pollen grains of 8 Tamarix species were collected from nature. Pollen grains were studied without any treatment. Measurements were based on at least 50 pollen grains per specimen. Light and scanning electron microscopes were used. Multivariate statistical methods were applied to clarify the species relationships based on pollen data. All species studied showed monad and tricolpate (except some individuals of T. androssowii). Some Tamarix species show a high level of variability, in response to ecological niches and phenotypic plasticity, which make Tamarix species separation much more difficult. Based on the results of the present study, pollen grains features are not in agreement with previous morphological and molecular genetics about the sectional distinction.

scholarly journals Pollen morphology of some Turkish Campanula spp. and their taxonomic value

1970 ◽  
Vol 37 (1) ◽  
pp. 33-42 ◽  
Author(s):  
Ismuhan Potoglu Erkara ◽  
Atila Ocak ◽  
Sevil Pehlivan
Keyword(s):  
Key Words ◽  
Pollen Morphology ◽  
Pollen Grains ◽  
Exine Sculpture ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
First Time ◽  
Scanning Electron

Detailed pollen morphological structures of 12 Turkish species of Campanula L., e.g. C. argaea, C. cymbalaria, C. glomerata subsp. hispida, C. latiloba subsp. latiloba, C. lyrata subsp. lyrata, C. olympica, C. persicifolia, C. pterocaula, C. rapunculoides subsp. cordifolia, C. rapunculus var. rapunculus, C. stricta var. stricta, C. pamphylica subsp. tokurii have been studied under light (LM) and scanning electron microscopes (SEM) for the first time. LM and SEM investigations show that the pollen grains of 12 taxa are more or less oblato-sphaeroidal, triporate (and/or tetraporate), tectum-scabrate, or with circular amb. The exine sculpture is granulate-scabrate in C. argaea, C. lyrata subsp. lyrata, C. stricta var. stricta, C. glomerata subsp. hispida and C. pamphylica subsp. tokurii; but those of C. cymbalaria, C. latiloba subsp. latiloba, C. olympica, C. persicifolia, C. pterocaula, C. rapunculoides subsp. cordifolia and C. rapunculus var. rapunculus are rugulate-scabrate.   Key words: Campanula, Pollen grains, Pollen morphology doi:10.3329/bjb.v37i1.1561 Bangladesh J. Bot. 37(1): 33-42, 2008 (June)

scholarly journals Corporate rating forecasting using Artificial Intelligence statistical techniques

2019 ◽  
Vol 16 (2) ◽  
pp. 295-312 ◽  
Author(s):  
Daniel Caridad ◽  
Jana Hančlová ◽  
Hosn el Woujoud Bousselmi ◽  
Lorena Caridad y López del Río
Keyword(s):  
Artificial Intelligence ◽  
Credit Rating ◽  
Financial Health ◽  
Multivariate Statistical Methods ◽  
Multivariate Statistical ◽  
Rating Agencies ◽  
Large Samples ◽  
Public Data ◽  
High Level

Forecasting companies long-term financial health is provided by Credit Rating Agencies (CRA) such as S&P, Moody’s, Fitch and others. Estimates of rates are based on publicly available data, and on the so-called ‘qualitative information’. Nowadays, it is possible to produce quite precise forecasts for these ratings using economic and financial information that is available in financial databases, utilizing statistical models or, alternatively, Artificial Intelligence techniques. Several approaches, both cross section and dynamic are proposed, using different methods. Artificial Neural Networks (ANN) provide better results than multivariate statistical methods and are used to estimate ratings within all the range provided by the CRAs, obtaining more desegregated results than several proposed models available for intervals of ratings. Two large samples of companies ‘public data’ obtained from Bloomberg are used to obtain forecasts of S&P and Moody’s ratings directly from these data with high level of accuracy. This also permits to check the published rating’s reliability provided by different CRAs.

Major element variations in ocean-floor basalts

1971 ◽  
Vol 268 (1192) ◽  
pp. 495-505 ◽  
Keyword(s):  
Statistical Methods ◽  
Major Element ◽  
Point Of View ◽  
Ocean Floor ◽  
Multivariate Statistical Methods ◽  
Calcic Plagioclase ◽  
Multivariate Statistical ◽  
Moderate Amount ◽  
High Level ◽  
Analytical Variation

Although ocean-floor basalts form a very convergent group from the point of view of their major element compositions, the variation that they do show can be interpreted in geological terms to a certain extent, though analytical variation must contribute substantially to that observed. Multivariate statistical methods demonstrate a high-level fractional crystallization trend in 94 selected ocean-floor basalts caused by precipitation of calcic plagioclase, forsteritic olivine and augite. After this effect is subtracted, a moderate amount of variation remains which can be interpreted as caused by crystal-liquid processes involving amphibole, though this is less certain. A new average of ocean-floor basalt compositions is presented, and it is suggested that the term ‘oceanic tholeiite’ should not be retained.

scholarly journals Pollen morphology of some Turkish Ajuga L. (Lamiaceae) and its taxonomic value

1970 ◽  
Vol 40 (1) ◽  
pp. 29-33 ◽  
Author(s):  
Yavuz Bulent Kose ◽  
Ismahan Potoglu Erkara ◽  
Sevim Alan
Keyword(s):  
Key Words ◽  
Pollen Morphology ◽  
Pollen Grains ◽  
Exine Sculpture ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
First Time ◽  
Scanning Electron

Pollen morphological structures of eight Turkish species of Ajuga, namely A. bombycina Boiss., A. chamaepitys (L.) Schreber ssp. chia var. chia (Schreber) Arcangeli, A. chamaepitys (L.) Schreber ssp. chia var. ciliata Briq., A. chamaepitys (L.) Schreber ssp. cuneatifolia (Stapf) P. H. Davis, A. genevensis L., A. laxmannii (L.) Benthum, A.orientalis L. and A. reptans L. have been studied under light and scanning electron microscopes for the first time. It is revealed that the pollen grains of Ajuga taxa are more or less suboblata-subprolata and tricolpatae. The exine sculpture is granulate in A. chamaepitys subsp. chia var. chia, A. chamaepitys subsp. cuneatifolia, A. genevensis, A. laxmannii, A. orientalis and A. reptans, but it is reticulate in A. bombycina and A. chamaepitys subsp. chia var. ciliata. Key words: Turkish Ajuga; Pollen morphology; Taxonomic value DOI: http://dx.doi.org/10.3329/bjb.v40i1.7994 Bangladesh J. Bot. 40(1): 29-33, 2011 (June)

scholarly journals POLLEN MORPHOLOGY OF LYCIUM (SOLANACEAE) SPECIES IN IRAN

2021 ◽  
Vol 56 ◽  
pp. 183-190
Author(s):  
Fatemeh MOUSAVIMANESH ◽  
◽  
Maryam KESHAVARZI ◽  
Zahra NAZEM BOKAEE ◽  
◽  
...  
Keyword(s):  
Pollen Morphology ◽  
Pollen Grains ◽  
Identification Problems ◽  
Multivariate Statistical ◽  
Qualitative And Quantitative ◽  
Exine Sculpture ◽  
Solanaceae Species ◽  
Palynological Study ◽  
First Time ◽  
Diagnostic Importance

Lycium (Solanaceae) has more than 100 species in arid and semi-arid parts of the world. In Iran, this medicinal plant is represented by 6 species, on which no palynological study has been conducted. Pollen morphology of 7 taxa are considered for the first time to evaluate the species relationships based on palynological data. Observations were made by use of Scanning electron microscopy on untreated pollen grains. Multivariate statistical analyses were carried out for qualitative and quantitative pollen features in the species studied. Results show that all pollen grains were monad, isopolar, zonotricolporate in prolate and preprolate shape. Exine sculpture was of striate and regulate patterns. Variations in pollen grains are considered to overcome the identification problems in species separation in morphologically similar taxa in this genus in Iran. The importance of pollen features in delimitation in some genera of Solanaceae was previously proven and the present study elucidates that some features as exine sculpture and some quantitative characters are of diagnostic importance in Lycium species native to Iran.

scholarly journals Main directions of the study of plant invasions in Russia

2021 ◽  
Vol 9 (4) ◽  
pp. 45-56
Author(s):  
Valeriy K. Tokhtar ◽  
Yulia K. Vinogradova ◽  
Alexander A. Notov ◽  
Аndrey Yu. Kurskoy ◽  
Elena S. Danilova
Keyword(s):  
Invasive Species ◽  
Alien Species ◽  
Statistical Methods ◽  
Plant Invasion ◽  
Species Group ◽  
Ecological Niches ◽  
Multivariate Statistical Methods ◽  
Multivariate Statistical ◽  
Alien Plant ◽  
Invasive Flora

Abstract This article is focused on the analysis of major approaches to plant invasion research used by Russian researchers. They fall within three main groups: 1. Conventional approaches to floristic analysis based on the Russian scientific tradition of floristic research, 2. Approaches focused on the study of the fraction of invasive flora, making blacklists and regional Black books, 3. New comprehensive approaches based on a synthesis of methods used in botany, geo-information technology and population genetics. Multivariate statistical methods allow for the visualization of various data, including those on alien species group structures in various regions. They make it possible to identify boundaries of ecological niches occupied by plants in respect to climate-and-environmental or ecological variables. An assessment of current statistical interdependence between alien plant characteristics and scores of factors limiting their dissemination facilitates the making of predictive models of plant invasion. Examples of multivariate statistical methods used in invasion biology were analyzed, along with different approaches to the study of the variability of alien species. Alien and invasive fractions of the flora of the Trans-Siberian Railway were analyzed not by administrative units but by natural biomes. This approach allowed us to assess the correlation between the number of invasive species with different natural-climatic and floristic characteristics of biomes. The publication of "Black Books" of various administrative subjects of Russia according to a unified methodology allowed us to make an inventory of invasive species over the vast territory of the country. The experience gained by Russian researchers may be further used for developing universal approaches to plant invasion research.

A standard organic sample for evaluating the imaging capabilities of Scanning Electron Microscopes

1994 ◽  
Vol 52 ◽  
pp. 1020-1021
Author(s):  
Patrick Echlin
Keyword(s):  
Noble Metals ◽  
Pollen Grains ◽  
Polystyrene Spheres ◽  
Medical Laboratories ◽  
Organic Sample ◽  
Digital Scanning ◽  
Electron Microscopes ◽  
Beam Currents ◽  
Scanning Electron Microscopes ◽  
Scanning Electron

We have been evaluating several digital scanning electron microscopes prior to the eventual purchase of an instrument. Most manufacturers demonstrate the capabilities of their instruments by using test specimens such as ultra-thin films of sputtered or evaporated noble metals, semi-conductors and photo resists and highly polished multi-compositional specimens made up of light and heavy elements. The microscope we need will be used for imaging and analysis by people from bio-medical laboratories and we are particularly interested in the quality of images we can obtain at low voltages and low beam currents from uncoated and coated samples and whether the specimens suffer any contamination and beam damage during examination and analysis. We do not envisage working at accelerating voltages much above 15keV. We needed a standard organic sample which was stable and easy to prepare and representative of the type of material we would be examining in the microscope we will eventually purchase. After investigating polystyrene spheres and a number of more natural bio-organic samples, including coffee creamer, starch, flour, pollen grains and spores we discovered that spray dried milk is an ideal sample to use for these instrumental evaluations.

scholarly journals On the Sub-Nanometer Resolution of Scanning Electron and Helium Ion Microscopes

2009 ◽  
Vol 17 (2) ◽  
pp. 6-13 ◽  
Author(s):  
András E. Vladár ◽  
Michael T. Postek ◽  
Bin Ming
Keyword(s):  
High Resolution ◽  
Lattice Spacing ◽  
Nanometer Scale ◽  
The Past ◽  
Helium Ion ◽  
Dimensional Measurements ◽  
Electron Microscopes ◽  
High Level ◽  
Scanning Electron Microscopes ◽  
Scanning Electron

All forms of microscopy are being pushed to the limit by nanotechnology. This is especially true for high-resolution scanning electron and helium ion microscopes, which are proving to be extremely useful for nanometer-scale imaging, characterization, and dimensional measurements. Excellent resolution is essential for imaging nanomaterials. Hence, there is a relentless quest to achieve better and better resolution with various electron and ion microscopes and to monitor and maintain these instruments to achieve the best possible performance levels.The ability to resolve fine details with a microscope has greatly improved over the past 20 years. The resolution achievable with the newest scanning electron microscopes (SEMs) can now be at or below 0.4 nm and for the scanning helium ion microscope (HeIM), 0.24 nm has been reported. To put this into perspective, the {111} crystal plane in silicon (Si) has 0.32 nm lattice spacing, so one cubic nanometer in the Si crystal contains only a few atoms. Therefore, an instrument must be performing at the highest level possible to resolve routinely the finest structures. Clearly, the instrument operator must also be functioning at a high level as well to achieve the best resolution and to prove that the instrument is capable of doing the work.

scholarly journals Palynological features of eleven Aethionema taxa from Turkey and their systematic implications

2017 ◽  
Vol 24 (2) ◽  
pp. 197-204 ◽  
Author(s):  
Mehmet Cengiz Karaismailoglu
Keyword(s):  
Pollen Morphology ◽  
Pollen Grains ◽  
Plant Taxon ◽  
Surface Ornamentation ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Scanning Electron

Pollen morphology of 11 taxa, including 2 endemic of the genus Aethionema W.T. Aiton from Turkey was examined under light and scanning electron microscopes. The pollens of Aethionema are mostly isopolar and bilaterally symmetric; spheroidal, prolate, perprolate and subprolate with the polar axes 14.07-26.41 μm and the equatorial axes 7.85-22.02 μm; mostly tricolpate, rarely 2-colpate; surface ornamentation is micro or macro reticulate. The exine thickness varies between 0.66 and 1.91 μm, and in tine thickness ranges from 0.27 to 0.85 μm. It is found that dimension of pollen grains, surface ornamentation, apocolpidium and amb diameter are taxonomically significant.Bangladesh J. Plant Taxon. 24(2): 197-204.

Toward High-Resolution Low-Voltage SEM

1988 ◽  
Vol 46 ◽  
pp. 218-219
Author(s):  
Zhifeng Shao
Keyword(s):  
Low Voltage ◽  
Spherical Aberration ◽  
Chromatic Aberration ◽  
Limiting Factor ◽  
Operating Voltage ◽  
Probe Radius ◽  
Non Local ◽  
Electron Microscopes ◽  
Image Position ◽  
Scanning Electron Microscopes

Recently, low voltage (≤5kV) scanning electron microscopes have become popular because of their unprecedented advantages, such as minimized charging effects and smaller specimen damage, etc. Perhaps the most important advantage of LVSEM is that they may be able to provide ultrahigh resolution since the interaction volume decreases when electron energy is reduced. It is obvious that no matter how low the operating voltage is, the resolution is always poorer than the probe radius. To achieve 10Å resolution at 5kV (including non-local effects), we would require a probe radius of 5∽6 Å. At low voltages, we can no longer ignore the effects of chromatic aberration because of the increased ratio δV/V. The 3rd order spherical aberration is another major limiting factor. The optimized aperture should be calculated as

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