Helianthus annuus Embryogenesis: Embryo Sac Wall Projections Before and After Fertilization

1971 ◽  
Vol 132 (4) ◽  
pp. 367-371 ◽  
Author(s):  
William Newcomb ◽  
Taylor A. Steeves
Keyword(s):  
Helianthus Annuus ◽  
Embryo Sac ◽  
Before And After

Ultrastructure of the developing embryo sac of sunflower (Helianthus annuus) before and after fertilization

1991 ◽  
Vol 69 (1) ◽  
pp. 191-202 ◽  
Author(s):  
Hua Yan ◽  
Hong-Yuan Yang ◽  
William A. Jensen
Keyword(s):  
Plasma Membrane ◽  
Helianthus Annuus ◽  
Embryo Sac ◽  
Active Role ◽  
Central Cell ◽  
Wall Material ◽  
Young Embryo ◽  
Before And After ◽  
Membrane Contact ◽  
Female Germ Unit

The ultrastructure of the embryo sac of the sunflower (Helianthus annuus) was investigated before and after fertilization. In the young embryo sac, walls were observed that completely surrounded the egg, synergids, and the central cell. However, as maturation continued, the extent of the wall changed. By the time the embryo was mature, the chalazal portion of the walls of the egg and synergids had disappeared so these cells have a plasma membrane to plasma membrane contact. This is also true for the central cell, which has plasma membrane contact with the egg and synergids. However, the chalazal and lateral walls of the central cell become considerably thicker at this time. Before the entry of the pollen tube, the synergid that is located toward the placenta degenerates. After fertilization, a wall forms over the chalazal portion of the zygote and the persistent synergid. The endosperm appears to play an active role in this process, contributing substantial amounts of wall material. However, the wall covering the chalazal portion of the zygote is not complete by the time the zygote divides. In the proembryo, ribosome density increases and lipid bodies decrease in number. The suspensory cell has autophagic vacuoles that encircle some of the organelles. Our results support the concept that the egg, synergids, and central cell form a single functional unit, the female germ unit. Key words: sunflower, ultrastructure, embryo sac, female germ unit.

The development of the embryo sac of sunflower Helianthus annuus after fertilization

1973 ◽  
Vol 51 (5) ◽  
pp. 879-890 ◽  
Author(s):  
William Newcomb
Keyword(s):  
Helianthus Annuus ◽  
Mitotic Spindle ◽  
Embryo Sac ◽  
Endosperm Development ◽  
Primary Endosperm Nucleus ◽  
Single Row ◽  
Wall Formation ◽  
Globular Stage ◽  
Spindle Apparatus ◽  
Single Fertilization

The degeneration of one synergid denotes the initiation of embryo and endosperm development in the embryo sac of sunflower Helianthus annuus L. The other synergid, the persistent synergid, is present until the late globular stage of embryogenesis. The primary endosperm nucleus divides before the zygote nucleus forming a coenocytic nuclear endosperm. When about eight endosperm nuclei are present during the early globular stage of embryogenesis, endosperm wall formation starts at the micropylar end of the embryo sac. The walls continue to grow toward the chalazal end of the embryo sac apparently as a result of the activity of Golgi located at the tips of the growing walls. Most endosperm wall formation is not associated with a mitotic spindle apparatus in sunflower. The suspensor of the embryo consists of a large basal cell during the proembryo stages, a single row of cells during the early globular stages, and at the late globular stage a double tier of cells near the radicle end of the embryo and a single row at the micropylar end of the embryo sac. Occasionally embryo development occurs in the absence of endosperm when only single fertilization has taken place. The development and nutritional implications of post-fertilization events in the sunflower embryo sac are discussed.

DEVELOPMENT OF THE EMBRYO SAC AND EMBRYO OF TEFF, ERAGROSTIS TEF

1966 ◽  
Vol 44 (8) ◽  
pp. 1071-1075 ◽  
Author(s):  
Melak H. Mengesha ◽  
A. T. Guard
Keyword(s):  
Female Gametophyte ◽  
Leaf Blade ◽  
Floral Development ◽  
Flag Leaf ◽  
Embryo Sac ◽  
Eragrostis Tef ◽  
Careful Study ◽  
Embryo Formation ◽  
Self Pollination ◽  
Before And After

A careful study of the floral development of Eragrostis tef indicates that the flowers do not open and that self-pollination is the rule. Observations of the development of the female gametophyte show that it is of the normal monosporic type common to most angiosperms. The three antipodals divide several times as is common in grasses. Study of many ovules before and after fertilization showed absence of any apomictic type of embryo formation. Fertilization was found to occur in the basal floret of a spikelet when that floret was at the base of the flag leaf blade.

Optimization of extraction conditions of antioxidants from sunflower shells (Helianthus annuus L.) before and after enzymatic treatment

2011 ◽  
Vol 33 (1) ◽  
pp. 123-131 ◽  
Author(s):  
Aleksandra Szydłowska-Czerniak ◽  
Konrad Trokowski ◽  
Edward Szłyk
Keyword(s):  
Helianthus Annuus ◽  
Enzymatic Treatment ◽  
Helianthus Annuus L ◽  
Before And After

Changes in poly(A) RNA and TMG snRNA distribution in the embryo sac of Hyacinthus orientalis L. before and after fertilization

2008 ◽  
Vol 21 (4) ◽  
pp. 247-257 ◽  
Author(s):  
Szymon Pięciński ◽  
Dariusz Jan Smoliński ◽  
Krzysztof Zienkiewicz ◽  
Elżbieta Bednarska
Keyword(s):  
Embryo Sac ◽  
Before And After ◽  
Hyacinthus Orientalis

scholarly journals Embryo development in Carica papaya Linn

2021 ◽  
Author(s):  
Miguel Acevedo-Benavides ◽  
Pablo Bolaños-Villegas
Keyword(s):  
Cell Fate ◽  
Female Gametophyte ◽  
Carica Papaya ◽  
Genetic Regulation ◽  
Draft Genome ◽  
Embryo Sac ◽  
Egg Cell ◽  
Parental Line ◽  
Before And After ◽  
Autonomous Development

ABSTRACTPapaya (Carica papaya Linn.) is a tropical plant whose draft genome has been sequenced. Papaya produces large fruits rich in vitamins A and C and is an important cash crop in developing countries. Nonetheless, little is known about how the female gametophyte develops, how it is fertilized and how it develops into a mature seed containing an embryo and an endosperm. The Papaya female gametophyte displays a Polygonum-type architecture consisting of two synergid cells, an egg cell, a central cell, and three antipodal cells. Reports are available of the presumed existence of varieties in which cross fertilization is bypassed and autonomous development of embryos occurs (e.g., apomixis). In this study, we analyzed the development of female gametophytes in a commercial Hawaiian parental line and in the presumed apomictic Costa Rican line L1. Samples were collected before and after anthesis to compare the overall structure, size and transcriptional patterns of several genes that may be involved in egg and endosperm cell fate and proliferation. These genes were the putative papaya homologs of ARGONAUTE9 (AGO9), MEDEA (MEA), RETINOBLASTOMA RELATED-1 (RBR1), and SLOW WALKER-1 (SWA1). Our results suggest that its feasible to identify the contour of structural features of Polygonum-type development, and that in bagged female flowers of line L1 we might have observed autonomous development of embryo-like structures. Possible downregulation of papaya homologs for AGO9, MEA, RBR1 and SWA1 was observed in embryo sacs from line L1 before and after anthesis, which may suggest a tentative link between suspected apomixis and transcriptional downregulation of genes for RNA-directed DNA methylation, histone remodelers, and rRNA processing. Most notably, the large size of the papaya embryo sac suggests that it could be a cytological alternative to Arabidopsis thaliana for study. Significant variation in embryo sac size was observed between the varieties under study, suggesting wide differences in the genetic regulation of anatomical features.

The development of the embryo sac of sunflower Helianthus annuus before fertilization

1973 ◽  
Vol 51 (5) ◽  
pp. 863-878 ◽  
Author(s):  
William Newcomb
Keyword(s):  
Endoplasmic Reticulum ◽  
Helianthus Annuus ◽  
Rough Endoplasmic Reticulum ◽  
Lipid Droplets ◽  
Embryo Sac ◽  
Egg Cell ◽  
Electron Microscopic ◽  
Linear Tetrad ◽  
Golgi Bodies ◽  
Large Clusters

The megaspore mother cell of sunflower Helianthus annuus L. undergoes two meiotic divisions to form a linear tetrad of haploid megaspores. The chalazal megaspore increases in size while the other megaspores and the nucellus degenerate such that the integumentary tapetum is adjacent to the embryo sac. Mitotic divisions occur forming the coenocytic two- and four-nucleate embryo sacs and the seven- or eight-nucleate six-celled embryo sac. Electron-microscopic observations suggest that the antipodals are very active synthetically but start degenerating before fertilization. Similarly the synergids are also apparently very active synthetically before fertilization as judged by the presence of extensive regions of dilated rough endoplasmic reticulum and many Golgi bodies and associated vesicles. The egg cell is characterized by the presence of many free ribosomes and small undifferentiated plastids. The central cell contains many circular strands of rough endoplasmic reticulum, lipid droplets, and large clusters of apparently active Golgi; it is a transfer cell resulting from the presence of embryo sac wall ingrowths. The development and the possible nutritional interrelationships of the megagametophyte and surrounding tissues are discussed.

Deformation Replication

1970 ◽  
Vol 28 ◽  
pp. 280-281
Author(s):  
J. Temple Black
Keyword(s):  
Cutting Speed ◽  
Machining Process ◽  
Depth Of Cut ◽  
Rake Face ◽  
Orthogonal Machining ◽  
Aluminum Chips ◽  
Before And After ◽  
Materials Used ◽  
Glass Knife ◽  
Very High

Tool materials used in ultramicrotomy are glass, developed by Latta and Hartmann (1) and diamond, introduced by Fernandez-Moran (2). While diamonds produce more good sections per knife edge than glass, they are expensive; require careful mounting and handling; and are time consuming to clean before and after usage, purchase from vendors (3-6 months waiting time), and regrind. Glass offers an easily accessible, inexpensive material ($0.04 per knife) with very high compressive strength (3) that can be employed in microtomy of metals (4) as well as biological materials. When the orthogonal machining process is being studied, glass offers additional advantages. Sections of metal or plastic can be dried down on the rake face, coated with Au-Pd, and examined directly in the SEM with no additional handling (5). Figure 1 shows aluminum chips microtomed with a 75° glass knife at a cutting speed of 1 mm/sec with a depth of cut of 1000 Å lying on the rake face of the knife.

The Clinical, Roentgenological and Morphological Effects of an Acute Exposure of Phosgene on the Lungs of Dogs

1971 ◽  
Vol 29 ◽  
pp. 236-237
Author(s):  
R. F. Bils ◽  
W. F. Diller ◽  
F. Huth
Keyword(s):  
Latent Period ◽  
Chemical Industry ◽  
Toxic Substance ◽  
Lung Edema ◽  
X Rays ◽  
Beagle Dogs ◽  
Male And Female ◽  
Morphological Alterations ◽  
Before And After ◽  
Electron Microscopes

Phosgene still plays an important role as a toxic substance in the chemical industry. Thiess (1968) recently reported observations on numerous cases of phosgene poisoning. A serious difficulty in the clinical handling of phosgene poisoning cases is a relatively long latent period, up to 12 hours, with no obvious signs of severity. At about 12 hours heavy lung edema appears suddenly, however changes can be seen in routine X-rays taken after only a few hours' exposure (Diller et al., 1969). This study was undertaken to correlate these early changes seen by the roengenologist with morphological alterations in the lungs seen in the'light and electron microscopes.Forty-two adult male and female Beagle dogs were selected for these exposure experiments. Treated animals were exposed to 94.5-107-5 ppm phosgene for 10 min. in a 15 m3 chamber. Roentgenograms were made of the thorax of each animal before and after exposure, up to 24 hrs.

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