Chromosome instability in Coix gigantea Koen. (Maydeae)

1984 ◽  
Vol 26 (3) ◽  
pp. 334-338 ◽  
Author(s):  
A. Nirmala ◽  
Panuganti N. Rao
Keyword(s):  
Chromosome Number ◽  
Chiasma Frequency ◽  
Seed Set ◽  
Chromosome Instability ◽  
Pollen Grains ◽  
Chromosomal Variation ◽  
Tolerance Limits ◽  
Genomic Plasticity ◽  
Tapetal Cells ◽  
Chromosome Fragments

In Coix gigantea Koen. (2n = 20), six of the plants that survived in the progenies raised from seed collected from Madhya Pradesh showed wide intraplant variation in chromosome number and behaviour. The chromosome number varied from 2n = 7 to 29. Higher configurations involving up to 10 chromosomes were found, though associations of 3 and 4 chromosomes were more prevalent. Univalents were also fairly common. Further, chromosome fragments ranging from one to three per cell were found in several of the cells. Similar variations in chromosome number and fragments were also observed in tapetal cells. Chromosomal associations and chiasma frequency were studied in each of the chromosome classes. Laggards, ranging from one to five were observed at anaphase I and II. Pollen grains were polymorphic and completely sterile, and there was no seed set. The instability was considered as part of the genomic plasticity, coupled with polyploidy, serving to enlarge the cytogenetic diversity in the species. However, it occurs in this population to levels beyond the tolerance limits of the genome affecting the fitness of the individual.Key words: Coix, chromosomal variation.

CHROMOSOMAL INSTABILITY IN A HYBRID BETWEEN HORDEUM VULGARE AND SECALE VAVILOVII

1982 ◽  
Vol 24 (2) ◽  
pp. 207-212 ◽  
Author(s):  
George Fedak ◽  
Chiharu Nakamura
Keyword(s):  
Hordeum Vulgare ◽  
Chromosome Number ◽  
Chiasma Frequency ◽  
Chromosomal Instability ◽  
Chromosome Instability ◽  
Somatic Tissue ◽  
Unreduced Gamete ◽  
Hordeum Vulgare L ◽  
The Mean

A hybrid was obtained between Hordeum vulgare L. cv. Betzes (2n = 2x = 14) and Secale vavilovii [Nürn. (2n = 2x = 14)] in which chromosome instability was observed in somatic and meiotic tissues. In somatic tissue the chromosomes per cell varied from 7 to 24 with a mean of 19.7. Similarly in meiotic tissue the chromosome number varied from 14 to 26 with a mean of 18.3. The mean chiasma frequency was 12.9 consisting of an average Ml configuration of 0.02IV + 0.3III + 6.68II + 3.92I. It was concluded that the hybrid was derived from the union of an unreduced gamete from Betzes barley with a normal gamete from S. vavilovii.

Cytoembryology of Amaryllis hybrids

1989 ◽  
Vol 67 (3) ◽  
pp. 839-847 ◽  
Author(s):  
Tasneem F. Khaleel ◽  
Daniel Siemsen
Keyword(s):  
Chromosome Number ◽  
Seed Set ◽  
Karyotype Analysis ◽  
Pollen Grains ◽  
Basic Chromosome Number ◽  
Archesporial Cell ◽  
Anther Wall ◽  
Basic Chromosome ◽  
Development Of Gametophytes ◽  
Secretory Type

Karyotype analysis, sporogenesis, and the development of gametophytes are described for four hybrids of garden Amaryllis. The basic chromosome number is x = 11, and all four hybrids are tetraploid. The basikaryotype, which consists of two median, five submedian, and four subterminal chromosomes, is traceable in four hybrids. The anther wall is five to six layered. The tapetum is of the secretory type, and its cells become two nucleate at the onset of meiosis in the microsporocytes. Bivalents, trivalents, and quadrivalents are formed during meiosis. The endothecial cells lack fibrillar thickenings. Pollen grains are shed at the two-celled stage. About 60–70% of the pollen grains are fertile. Ovules are anatropous and bitegmic. The archesporial cell may or may not undergo periclinal division. Development of the megagametophyte is monosporic in 90% of the ovules and bisporic in the remaining 10%. All four hybrids show degeneration of embryo sacs at various stages of development which accounts for the low percentage or lack of seed set.

scholarly journals Taxonomic Description and Reproductive Behavior of Giant Pangola (Digitaria valida Stent)

1969 ◽  
Vol 44 (2) ◽  
pp. 53-59
Author(s):  
A. Sotomayor-Ríos ◽  
K. F. Schertz ◽  
R. Woodbury ◽  
J. Vélez Fortuño
Keyword(s):  
Chromosome Number ◽  
Reproductive Behavior ◽  
Somatic Chromosome ◽  
Seed Set ◽  
Pollen Grains ◽  
Breeding Program ◽  
Chromosome Constitution ◽  
Low Fertility ◽  
Taxonomic Description ◽  
Multivalent Formation

The chromosome number and reproductive behavior of Giant Pangola, a type of Digitaria valida Stent, were determined to evaluate the possibility of using it in a breeding program. It was also described and verified taxonomically. The observations revealed anomalies which would appear to severely handicap its use in breeding. The somatic chromosome constitution of 42 is different from those previously reported for this species. Microsporogenesis was irregular in all cells studied, characterized by multivalent formation, lagging univalents, and micronuclei, and resulted in only 2.3 percent of the pollen grains staining completely in IKI solution. No degeneration was observed during megasporogenesis but was usually apparent after megaspore formation. It is concluded that the chromosomal irregularities noted may be sufficient to cause the very low seed set and that this low fertility will limit the utilization of Giant Pangola in a breeding program.

POLLEN PRODUCTION AND DISSEMINATING PROPERTIES OF TRITICALE RELATIVE TO WHEAT

1972 ◽  
Vol 52 (4) ◽  
pp. 569-574 ◽  
Author(s):  
K. C. YEUNG ◽  
E. N. LARTER
Keyword(s):  
Seed Set ◽  
Marker Gene ◽  
Pollen Grains ◽  
Triticum Aestivum L ◽  
Hybrid Seed Production ◽  
Pollen Production ◽  
Hexaploid Triticale ◽  
Anther Length ◽  
Anther Extrusion ◽  
Wide Range

A study of the pollen production properties of three hexaploid triticale strains (Triticale hexaploide Lart.) showed that their anther length was significantly greater than that of wheat anthers (Triticum aestivum L. em Thell.) and the estimated number of pollen grains per anther ranged from 15,000 to 21,000. In comparison, a total of 8000 grains per anther was estimated for wheat, cult Manitou. Eighty-nine percent anther extrusion occurred in triticale cult Rosner, while Manitou averaged 70% anther extrusion. The period of anthesis of triticale varied according to strain but generally was of longer duration than in Manitou and thereby promoted outcrossing. Using a triticale strain carrying a dominant marker gene, 50% seed-set was obtained at a distance of 12 m leeward of the pollen source; however, a small percentage was still obtained at a distance of 30 m. It would appear from the limited number of triticales used in this study that a wide range of variability exists within this species in its pollen production and disseminating properties. With appropriate selection pressures, strains with an outbreeding habit could be developed for the purpose of hybrid seed production.

Aspidistra revoluta, a new species from limestone areas in Chongqing, China

Phytotaxa ◽  
2016 ◽  
Vol 257 (3) ◽  
pp. 280 ◽  
Author(s):  
Hao Zhou ◽  
Si-rong Yi ◽  
Qi Gao ◽  
Jie Huang ◽  
Yu-jing Wei
Keyword(s):  
New Species ◽  
Chromosome Number ◽  
Average Length ◽  
Chromosome Complement ◽  
Pollen Grains ◽  
The Other ◽  
Morphological Comparison ◽  
Chongqing Municipality ◽  
Karyotype Asymmetry ◽  
A New Species

Aspidistra revoluta (Asparagaceae) is described and illustrated as a new species from limestone areas in southern Chongqing Municipality, China. The new species can be distinguished from the other Aspidistra species by its unique umbrella-like pistil with large revolute stigma lobes that bent downwards and touch the base of the perigone. A detailed morphological comparison among A. revoluta, A. nanchuanensis and A. carnosa is provided. The pollen grains of A. revoluta are subspherical and inaperturate, with verrucous exine. The chromosome number is 2n = 38, and the karyotype is formulated as 2n = 22m + 6sm + 10st. The average length of chromosome complement is 4.50 μm, and the karyotype asymmetry indexes A1 and A2 are respectively 0.37±0.03 and 0.49±0.01.

CYTOLOGY OF 2n POLLEN FORMATION IN DIPLOID ALFALFA, MEDICAGO SATIVA

1979 ◽  
Vol 21 (4) ◽  
pp. 525-530 ◽  
Author(s):  
Nicholi Vorsa ◽  
E. T. Bingham
Keyword(s):  
Medicago Sativa ◽  
Seed Set ◽  
Pollen Grains ◽  
Genetic Constitution ◽  
2N Pollen ◽  
Diploid Parent ◽  
2N Gamete ◽  
Medicago Sativa L ◽  
Pollen Formation ◽  
Mother Cells

Four diploid (2x) clones of alfalfa, Medicago sativa L., which produced good seed set when used as male parents in 4x-2x crosses were selected for study. The 2x clones descended from 2x haploids of cultivated 4x alfalfa. Fertility in the 4x-2x cross was due to the production of pollen with the unreduced chromosome number (2n pollen) from the 2x parent. The cytological mechanism of 2n pollen formation was found to be disorientation of spindles at metaphase II in up to 38% of the pollen mother cells. Thus, both n and 2n pollen were produced by all four diploids examined. Normal spindles at metaphase II were oriented such that they defined the poles of a tetrahedron and resulted in normal tetrads in a tetrahedral arrangement. Disoriented spindles were basically parallel to each other and resulted in formation of dyads and occasionally a triad. Dyads developed into two 2n pollen grains; triads developed into one 2n and two n pollen grains. Since both n and 2n pollen grains are produced by the diploids, they can be maintained as diploids or they can be used as male parents in crosses to tetraploids. The genetic constitution of 2n pollen resulting from parallel spindles is similar to that expected after first division restitution of meiosis and much of the heterozygosity of the diploid parent is conserved in the gametes. The 2n gamete mechanism has potential application in germplasm transfer and in maximizing heterozygosity in tetraploid hybrids.

scholarly journals Pollen, Tapetum, and Orbicule Development inColletia paradoxaandDiscaria americana(Rhamnaceae)

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
M. Gotelli ◽  
B. Galati ◽  
D. Medan
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Pollen Grains ◽  
Pollen Grain ◽  
Ultrastructural Changes ◽  
Transmission Electron ◽  
The Family ◽  
Tapetal Cells ◽  
Grain Formation

Tapetum, orbicule, and pollen grain ontogeny inColletia paradoxaandDiscaria americanawere studied with transmission electron microscopy (TEM). The ultrastructural changes observed during the different stages of development in the tapetal cells and related to orbicule and pollen grain formation are described. The proorbicules have the appearance of lipid globule, and their formation is related to the endoplasmic reticulum of rough type (ERr). This is the first report on the presence of orbicules in the family Rhamnaceae. Pollen grains are shed at the bicellular stage.

scholarly journals Why so many flowers? A preliminary assessment of mixed pollination strategy enhancing sexual reproduction of the invasive <i>Acacia longifolia</i> in Portugal

Web Ecology ◽  
2018 ◽  
Vol 18 (1) ◽  
pp. 47-54 ◽  
Author(s):  
Manuela Giovanetti ◽  
Margarida Ramos ◽  
Cristina Máguas
Keyword(s):  
Invasive Plant ◽  
Seed Set ◽  
Pollen Grains ◽  
Striking Difference ◽  
Pollination Syndromes ◽  
Pollination Success ◽  
Relative Contribution ◽  
Acacia Longifolia ◽  
Exclusion Experiments ◽  
Pollination Strategy

Abstract. Acacia longifolia, a native legume from Australia, has been introduced in many European countries and elsewhere, thus becoming one of the most important global invasive species. In Europe, its flowering occurs in a period unsuitable for insect activity: nonetheless it is considered entomophilous. Floral traits of this species are puzzling: brightly coloured and scented as liked by insects, but with abundant staminate small-sized flowers and relatively small pollen grains, as it is common in anemophilous species. Invasion processes are especially favoured when reshaping local ecological networks, thus the interest in understanding pollination syndromes associated with invasive plant species that may facilitate invasiveness. Moreover, a striking difference exists between its massive flowering and relatively poor seed set. We introduced a novel approach: first, we consider the possibility that a part of the pollination success is carried on by wind and, second, we weighted the ethological perspective of the main pollinator. During the flowering season of A. longifolia (February–April 2016), we carried on exclusion experiments to detect the relative contribution of insects and wind. While the exclusion experiments corroborated the need for pollen vectors, we actually recorded a low abundance of insects. The honeybee, known pollinator of acacias, was relatively rare and not always productive in terms of successful visits. While wind contributed to seed set, focal observations confirmed that honeybees transfer pollen when visiting both the inflorescences to collect pollen and the extrafloral nectaries to collect nectar. The mixed pollination strategy of A. longifolia may then be the basis of its success in invading Portugal's windy coasts.

scholarly journals Dynamics of Polysaccharides and Neutral Lipids during Anther Development in Castor (Ricinus communis)

2015 ◽  
Vol 140 (4) ◽  
pp. 356-361 ◽  
Author(s):  
Dongmei Wei ◽  
Huimin Xu ◽  
Ruili Li
Keyword(s):  
Neutral Lipids ◽  
Ricinus Communis ◽  
Starch Content ◽  
Single Layer ◽  
Pollen Grains ◽  
Middle Layer ◽  
Anther Development ◽  
Anther Wall ◽  
Starch Grains ◽  
Tapetal Cells

Anthers contain starch and neutral lipids, which have key roles in microspore ontogeny and gametophyte development. In this study, we observed the dynamic changes in starch and neutral lipids in the anther developmental processes of castor (Ricinus communis) by cytochemical methods. Starch grains and neutral lipids presented a regular dynamic distribution during anther development. In young anthers, some neutral lipids accumulated in sporogenous cells, whereas neutral lipids disappeared with microspore growth. At the late microspore stage, starch grains began to accumulate in microspores, and the starch content of bicellular pollen significantly increased after microspore mitosis. At anthesis, starch grains and neutral lipids accumulated in the mature pollen grains. Visible changes occurred in anther wall cells. The epidermis, middle layer, and tapetum were degenerated, and only a single layer of endothecium remained at anthesis. The dynamic variation of starch grains and neutral lipids in tapetal cells was consistent with the changes in microspores and pollen during anther development. All these findings demonstrated that tapetal cells directly interacted with the developing gametophytes. The tapetal cells play an important role in supplying nutritional substances for microspore absorption. Moreover, the endothecium protects the pollen and contributes to anther dehiscence. The results of this study provide a foundation for the further research on sexual reproduction in angiosperms.

Palynological analysis of five selected Onosma taxa

Biologia ◽  
2008 ◽  
Vol 63 (2) ◽  
Author(s):  
Filippo Maggi ◽  
Vladislav Kolarčik ◽  
Pavol Mártonfi
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Chromosome Number ◽  
Pollen Grains ◽  
Pollen Size ◽  
Palynological Analysis ◽  
Positive Correlation ◽  
Pollen Characters ◽  
Scanning Electron

AbstractPollen size and exine structure of the following five Onosma L. species from Slovakia and Italy were studied by light and scanning electron microscopy: Onosma echioides, O. tornensis, O. visianii, O. arenaria, and O. pseudoarenaria. Among the taxa studied, O. echioides has the smallest pollen grains in average (10.5–17.5 × 8.0–14.5 µm), and O. pseudoarenaria the largest grains in average (15.3–20.5 × 12.3–16.3 µm). Pollen grains of all 5 species are small sized, 3-syncolporate, subprolate, heteropolar, with ovate equatorial outlines and circular to rounded triangular polar outlines; the tectum is microechinate. A positive correlation is found between pollen size and chromosome number. The value of pollen characters for taxonomic purposes and the position of the taxa studied within the genus Onosma are discussed.

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