scholarly journals Chromosome stickiness during meiotic behavior analysis of Passiflora serrato-digitata L. (PassifloraCEAE)

2011 ◽  
Vol 41 (6) ◽  
pp. 1018-1023 ◽  
Author(s):  
Paulo Roberto Peres Kiihl ◽  
Andréia Rodrigues Alonso Pereira ◽  
Sara Mataroli de Godoy ◽  
Neusa Maria Colauto Stenzel ◽  
Claudicéia Risso-Pascotto
Keyword(s):  
Behavior Analysis ◽  
Metaphase Plate ◽  
Meiotic Behavior ◽  
American Continent ◽  
Segregation Process ◽  
Ethanol Acetic Acid ◽  
Experimental Base ◽  
Chromosome Stickiness ◽  
First Time ◽  
Metaphase I

Almost 90% of species of the genus Passiflora are native to the American continent, with high commercial value due to the fact that some species are used for human food while others have ornamental and medical qualities. Passiflora serrato-digitata is one of the species that integrates the Paraná Agronomic Institute germoplasm bank at its experimental base in Londrina, PR, Brazil. Collected flower buds were fixed in ethanol/acetic acid (3:1 v/v) for 24h, transferred to 70% alcohol and stored under refrigeration. Slides were prepared by the squashing technique and stained with 1.0% propionic carmine; they were analyzed under an optic microscope. Irregularities in the chromosome segregation process of P. serrato-digitata have been verified by meiotic behavior analysis. These comprised precocious migration to poles in metaphase I and II, non-oriented chromosomes in metaphase plate in metaphase I and II, laggard chromosomes in anaphase I and II towards the formation of micronucleus in telophase I and II, and microspores in tetrads. Chromosome stickiness was another irregularity reported in the Passiflora genus for the first time. These irregularities which also contributed to the formation of monads, dyads and triads, resulted in normal imbalanced 2n and 4n microspores. According to the observed Meiotic Index of 71.83%, this species is not meiotically stable.

scholarly journals Ploidy level and obligate apogamy in two populations of Argyrochosma nivea var. tenera (Pteridaceae)

Hoehnea ◽  
2015 ◽  
Vol 42 (2) ◽  
pp. 233-237 ◽  
Author(s):  
Marcela A. Hernández ◽  
Aldo R. Andrada ◽  
Valeria de los A. Páez ◽  
Olga G. Martínez
Keyword(s):  
Meiotic Chromosome ◽  
Glandular Trichomes ◽  
Hybrid Origin ◽  
American Continent ◽  
Reproduction Mode ◽  
Ethanol Acetic Acid ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
First Time ◽  
Two Populations

ABSTRACT Argyrochosma nivea var. tenera is a cheilanthoid fern from the American continent. We present herewith the study of meiotic behavior and gametic number as well as number of spores and reproduction mode (with observations from cultured gametophytes). The study material is from Northwestern Argentina. For the study of meiosis, sporangia were fixed in ethanol-acetic acid (3:1) and stained with 2% propionic haematoxylin. Micrographs were taken using light and scanning electron microscopes. Meiotic chromosome number is 2n = 3x = 81 and the presence of lagging chromosomes at telophase II is mentioned for the first time; three sets of chromosome occur at diakinesis. Sporangia have 32 trilete spores. Adult gametophytes are laminar, cordiform, asymetrical, glabrous, without glandular trichomes. In our samples, the adult gametophytes were neuter, without antheridia or archegonia, with obligate apogamous reproduction. Both populations studied might be of hybrid origin.

The Strait of Magellan—a Gateway to New Worlds

2021 ◽  
Author(s):  
Mauricio Onetto Pavez
Keyword(s):  
Global Scale ◽  
Modern World ◽  
American Continent ◽  
The Earth ◽  
Starting Point ◽  
Strait Of Magellan ◽  
The World ◽  
The Strait Of Magellan ◽  
History Of ◽  
First Time

The year 2020 marks the five hundredth anniversary of the “discovery” of the Strait of Magellan. The unveiling of this passage between 1519 and 1522 allowed the planet to be circumnavigated for the first time in the history of humanity. All maritime routes could now be connected, and the idea of the Earth, in its geographical, cosmographic, and philosophical dimensions, gained its definitive meaning. This discovery can be considered one of the founding events of the modern world and of the process of globalization that still continues today. This new connectivity awoke an immediate interest in Europe that led to the emergence of a political consciousness of possession, domination, and territorial occupation generalized on a global scale, and the American continent was the starting point for this. This consciousness also inspired a desire for knowledge about this new form of inhabiting the world. Various fields of knowledge were redefined thanks to the new spaces and measurements produced by the discovery of the southern part of the Americas, which was recorded in books on cosmography, natural history, cartography, and manuscripts, circulating mainly between the Americas and Europe. All these processes transformed the Strait of Magellan into a geopolitical space coveted by Europeans during the 16th century. As an interoceanic connector, it was used to imagine commercial routes to the Orient and political projects that could sustain these dynamics. It was also conceived as a space to speculate on the potential wealth in the extreme south of the continent. In addition, on the Spanish side, some agents of the Crown considered it a strategic place for imperial projections and the defense of the Americas.

Metaphase position of an interchange quadrivalent of Allium triquetrum

1988 ◽  
Vol 90 (3) ◽  
pp. 493-499
Author(s):  
GEOFFREY K. RICKARDS ◽  
WENDY A. BAKER
Keyword(s):  
Linear Array ◽  
Metaphase Plate ◽  
Real Data ◽  
Slide Preparation ◽  
Metaphase I

The position of an interchange quadrivalent at metaphase I of Allium triquetrum was modelled so as to simulate the original placement of the quadrivalent in the spindle and the preparation of linear spreads through squashing. In this way an expected distribution for the quadrivalent in linear spreads was generated. The procedure used polar views of metaphase I to which the quadrivalent was assigned pairs of positions normally occupied by bivalents. The positions of the bivalents and assigned quadrivalent were then into a linear array and analysed as ‘real’ data. Comparisons with observed distributions showed that a general bias in favour of marginal placement of the quadrivalent in the linear array is expected; and also showed that the quadrivalent is positioned non-randomly in the metaphase plate prior to slide preparation.

scholarly journals Identification of a Marine Green Alga Percursaria percursa from Hypersaline Springs in the Middle of the North American Continent

2005 ◽  
Vol 119 (1) ◽  
pp. 82 ◽  
Author(s):  
Kathleen L. Londry ◽  
Pascal H. Badiou ◽  
Stephen E. Grasby
Keyword(s):  
Green Alga ◽  
Microbial Mat ◽  
American Continent ◽  
North American Continent ◽  
The North ◽  
Western Shore ◽  
Dominant Member ◽  
Hypersaline Springs ◽  
First Time ◽  
North Western

The chlorophycean alga Percursaria percursa (Ulvaceae, Ulvales, Chlorophyceae), typical of marine inter-tidal zones, is reported for the first time from hypersaline springs located along the north-western shore of Lake Winnipegosis in Manitoba. Although not usually found inland, P. percursa is the dominant member of microbial mat communities that thrive in shallow pools at the outlets of hypersaline springs.

scholarly journals Species Composition and New Records of Diatom Taxa on Phyllodictyon pulcherrimum (Chlorophyceae) from the Gulf of California

Diversity ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 339
Author(s):  
Francisco Omar López-Fuerte ◽  
David Alfaro Siqueiros Beltrones ◽  
María del Carmen Altamirano-Cerecedo
Keyword(s):  
Gulf Of California ◽  
New Records ◽  
American Continent ◽  
Epiphytic Diatoms ◽  
Taxonomic Analysis ◽  
The North ◽  
The Pacific ◽  
The Pacific Ocean ◽  
First Time ◽  
The North Pacific

A taxonomic analysis of diatoms found on Phyllodictyon pulcherrimum yielded a total of 244 diatom taxa (all illustrated) within 27 orders, 45 families, and 86 genera. The Taxa were briefly documented in a list including identification references and morphometric data. Thirty-eight of the taxa identified at the species and infraspecific levels represent new records for the coasts of Mexico. Seven were recorded for the first time on the American continent: Auricula flabelliformis, A. pulchra, Campylodiscus scalaris, Coscinodiscus mesoleius, Dimeregramma fulvum, Navicula palpebralis var. angulosa, and Seminavis barbarae, and one, Nitzschia fusiformis, for the Pacific Ocean. This is the second record of the chlorophyte P. pulcherrimum in the north Pacific and the third for Mexican waters. The results confirm that surveying rare macroalgae species as hosts for epiphytic diatoms provides opportunities to seek new records of diatom taxa, or even new taxa, in regions around the world.

scholarly journals The demography of the Canary Islands from a genetic perspective

2020 ◽  
Author(s):  
Rosa Fregel ◽  
Alejandra C Ordóñez ◽  
Javier G Serrano
Keyword(s):  
Canary Islands ◽  
Demographic History ◽  
American Continent ◽  
North African ◽  
European Colonization ◽  
History Of ◽  
The Impact ◽  
First Time ◽  
Canarian Archipelago ◽  
North African Origin

Abstract The establishment of European colonies across the world had important demographic consequences because it brought together diverse and distant civilizations for the first time. One clear example of this phenomenon is observed in the Canary Islands. The modern Canarian population is mainly the result of the admixture of natives of North African origin and European colonizers. However, additional migratory flows reached the islands due to the importation of enslaved Africans to cultivate sugarcane and the intense commercial contact with the American continent. In this review, we evaluate how the genetic analysis of indigenous, historical, and current populations has provided a glimpse into the Canary Islands’ complex genetic composition. We show that each island subpopulation’s characterization is needed to fully disentangle the demographic history of the Canarian archipelago. Finally, we discuss what research avenues remain to be explored to improve our knowledge of the impact that the European colonization had on its native population.

scholarly journals II.—The true date of the English Discovery of the American Continent under John and Sebastian Cabot

Archaeologia ◽  
1871 ◽  
Vol 43 (1) ◽  
pp. 17-42
Author(s):  
Richard Henry Major
Keyword(s):  
East Coast ◽  
North Coast ◽  
American Continent ◽  
Terra Firma ◽  
The North ◽  
Great Achievement ◽  
Entire Collection ◽  
To Come ◽  
First Time ◽  
Sound Judgment

While there remain any in this utilitarian age who value accuracy in history, the date of the discovery of the continent of America by English vessels will not be regarded as unimportant. It is well known that Columbus, whose great achievement of 1492 has placed him on a pinnacle of renown which neither rivalry nor detraction can ever eclipse or undermine, was himself preceded in the actual discovery of terra firma by John and Sebastian Cabot. It was not till 1498 that that prince of navigators lighted on the north coast of South America, whereas it is a fact beyond all question that in 1497 John Cabot, accompanied by his son Sebastian, was on the east coast of North America. The question is, whether in that year they discovered that coast for the first time, or whether in 1494 it had been already seen by them, though possibly not explored. Both these suppositions have had their advocates at different periods, but in later years the materials for forming a sound judgment on the question have much increased under our hands, and I should not be occupying your time now if I were not of opinion that the entire collection of documents in our possession is sufficient to enable us to come to a decided conclusion.

THE ULTRASTRUCTURE OF KINETOCHORES OF UNPAIRED CHROMOSOMES IN A WHEAT HYBRID

1973 ◽  
Vol 15 (4) ◽  
pp. 801-806 ◽  
Author(s):  
E. B. Wagenaar ◽  
D. F. Bray
Keyword(s):  
Sister Chromatid ◽  
Metaphase Plate ◽  
Polar Regions ◽  
Equatorial Plate ◽  
Univalent Chromosome ◽  
Wheat Hybrid ◽  
Opposite Pole ◽  
Kinetochore Region ◽  
Metaphase I

The kinetochore region of unpaired chromosomes (univalents) consists of two kinetochores, each belonging to a sister chromatid, that are located adjacent to one another on the surface of the univalent chromosome. This condition results in a movement by the univalent towards one of the polar regions at the onset of metaphase I. Once arrived in this region, one of the sister kinetochores obtains attachments of microtubules from the opposite pole. This results in a gradual return of the univalent to the equatorial plate, where it reaches an equilibrium. The sister kinetochores remain adjacent during the movement, but once arrived at the metaphase plate they develop a typical mitotic appearance, in which the sister kinetochores have opposite positions on the chromosomes.

THE IDENTIFICATION AND MEIOTIC BEHAVIOR OF A DITELOSOMIC LINE IN AVENA SATIVA L

1970 ◽  
Vol 12 (4) ◽  
pp. 876-881 ◽  
Author(s):  
J. P. Dubuc ◽  
R. C. McGinnis
Keyword(s):  
Avena Sativa ◽  
Reciprocal Translocation ◽  
Meiotic Behavior ◽  
Telocentric Chromosome ◽  
Chromosome 20 ◽  
Ditelosomic Line ◽  
Metaphase I

A ditelosomic line was crossed with 12 identified monosomics. The metaphase I pairing was studied in the 40 + t – chromosome progenies. The telocentric chromosome was found to be homologous to the three previously identified monosomics namely, −7, −10, and −20 suggesting that the same chromosome is missing in all three lines. None of the chromosomes in monosomic condition used in the crosses except ST-7 and ST-17 from A. byzantina were involved in the reciprocal translocation present between Sun II and Garry and Rodney.The gene for normal vs. abaxial curling of the leaves was located on the short arm of chromosome 20. The genes for diploidisation and normal vs. kinky neck were located on 20L.

scholarly journals Chromosome Number and Meiotic Behavior of Cultivated Chia, Salvia hispanica (Lamiaceae)

HortScience ◽  
1990 ◽  
Vol 25 (12) ◽  
pp. 1646-1647 ◽  
Author(s):  
A. Estilai ◽  
A. Hashemi ◽  
K. Truman
Keyword(s):  
Chromosome Number ◽  
Species Identification ◽  
Southern California ◽  
Herbarium Specimens ◽  
Meiotic Behavior ◽  
Root Tips ◽  
Chromosome Counts ◽  
Salvia Hispanica ◽  
Meiotic Analyses ◽  
Metaphase I

Edible chia seeds, purchased from the local markets in Guatemala, Mexico, and southern California, were used for species identification, chromosome counts, karyotype construction, and meiotic analyses. Plants raised from those seeds had ovate leaves, dense racemose inflorescences, pale-blue flowers, and were identified from herbarium specimens as Salvia hispanica L. Mitotic analyses of root tips from 50 plants showed 2n = 12—the lowest chromosome number in the genus. Chromosomes were small, ranging from 2 to 3.5 pm. One pair of chromosomes was metacentric (with the long arm: short arm ratio, r = 1.5), four pairs were submetacentric (r = 2.6 to 3.6), and one pair was telocentric (r = 12). Meiosis was regular and six bivalents were observed at metaphase I. Ring and rod bivalents averaged 1.53 ± 1.05 and 4.47 ± 1.05, respectively;

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