scholarly journals Early events during embryogenesis in Zea mays L.

2014 ◽  
Vol 50 (1-2) ◽  
pp. 289-290 ◽  
Author(s):  
A. A. Van Lammeren
Keyword(s):  
Zea Mays ◽  
Structural Changes ◽  
Zea Mays L ◽  
Mature Embryo ◽  
Early Embryogenesis ◽  
Central Cell ◽  
Egg Cell ◽  
Cellular Endosperm ◽  
Well Differentiated

The megagametophyte of <em>Zea mays</em> L. undergoes a series of structural changes after fertilization resulting in a well differentiated mature embryo and cellular endosperm at 480 hours after pollination in greenhouse conditions. In the present work emphasis was laid on the localization of the cytoplasm in the synergids, central cell-endosperm and egg cell-zygote prior to and after fertilization. The observations are discussed in relation to the process of early embryogenesis.

scholarly journals The ultrastructure of the mature embryo sac in the natural tetraploid of red clover (Trifolium pratense L.): that has a very low rate of seed formation

2014 ◽  
Vol 66 (1) ◽  
pp. 13-20 ◽  
Author(s):  
Gönül Algan ◽  
H. Nurhan Bakar
Keyword(s):  
Endoplasmic Reticulum ◽  
Trifolium Pratense ◽  
Embryo Sac ◽  
Red Clover ◽  
Mature Embryo ◽  
Polar Nucleus ◽  
Central Cell ◽  
Egg Cell ◽  
Ultrastructural Organization ◽  
Seed Formation

In this study, ultrastructural organization of cells in the mature embryo sac of natural tetraploid <em>Trifolium pratense</em> L. was investigated. The mature embryo sac of this plant contains an egg cell with two synergids at the micropylar end, and a central cell with two polar nuclei. The ultrastructure of these cells agrees with what is known for most angiosperms studied with the electron microscope. The egg cell is a large and highly vacuolate cell, partially surrounded by a wall. Much of the cytoplasm is located around the nucleus at the chalazal end and there are few numbers of channel-shaped endoplasmic reticulum, mitochondria, plastids and numerous ribosomes distributed throughout the cytoplasm. Unlike the egg cell, much of the cytoplasm in synergid cells is located at micropylar part of the cell and the synergid cytoplasm contains especially, large numbers of rough endoplasmic reticulum, free ribosomes, mitochondria and plastids. The central cell of <em>T. pratense</em> L. contains two large polar nuclei which lie close to the egg apparatus. Each polar nucleus has a single, large, dense nucleolus that contains several nucleolar vacuoles. Much of the central cell cytoplasm consisting of granular and agranular endoplasmic reticulum, mitochondria, plastids, ribosomes, dictyosomes and lipid bodies are placed around polar nuclei.

Early embryogenesis in Arabidopsis thaliana. I. The mature embryo sac

1991 ◽  
Vol 69 (3) ◽  
pp. 447-460 ◽  
Author(s):  
S. G. Mansfield ◽  
L. G. Briarty ◽  
S. Erni
Keyword(s):  
Arabidopsis Thaliana ◽  
Endoplasmic Reticulum ◽  
Embryo Sac ◽  
Mature Embryo ◽  
Central Cell ◽  
Egg Cell ◽  
Cell Cytoplasm ◽  
Intimate Contact ◽  
Egg Apparatus ◽  
Common Wall

Arabidopsis thaliana has a seven-celled eight-nucleate megagametophyte of the Polygonum type; each cell type displays a different form of structural specialization. The egg apparatus cells are highly polarized; the egg has a large micropylar vacuole and chalazally sited nucleus, whereas the opposite is true for the synergids. At the chalazal region of the egg apparatus cells there are no cell wall boundaries, although their plasmalemmas are in intimate contact. The common wall between the two synergids is thin and irregular and contains plasmodesmatal connections. The synergid cytoplasm is rich in organelles; profiles of rough endoplasmic reticulum appear in masses of parallel stacked cisternae, and large accumulations of mitochondria occur adjacent to the filiform apparatus. The egg cell cytoplasm is quiescent; ribosome concentration and frequencies of dictyosomes and endoplasmic reticulum are noticeably lower and plastids are poorly differentiated. The central cell is long and vacuolate with a large diploid nucleus; fusion of the polar nuclei occurs prior to embryo sac maturity. The cytoplasm contains numerous starch-containing plastids accumulated in a shell around the nucleus. A high ribosome concentration and the absence of vacuoles and dictyosomes typifies the antipodal cell cytoplasm. All antipodal cells are interconnected by plasmodesmata as well as being connected to the nucellus and central cell. Key words: Arabidopsis, embryo sac, embryogenesis, cell specializations, stereology.

Induction of bicellular pollen by trifluralin treatment and occurrence of triploids and aneuploids after fertilization in maize

Genome ◽  
1999 ◽  
Vol 42 (1) ◽  
pp. 154-157 ◽  
Author(s):  
Akio Kato
Keyword(s):  
Zea Mays ◽  
Effective Treatment ◽  
Key Words ◽  
Zea Mays L ◽  
Generative Cell ◽  
Pollen Grains ◽  
Aluminum Foil ◽  
Central Cell ◽  
Vegetative Nucleus ◽  
Chromosome Counts

By spraying tassels of maize (Zea mays L.) with a trifluralin solution before flowering, viable bicellular pollen grains (with one vegetative nucleus and one mitotically arrested diploid generative cell) were produced. Fertilization between a central cell (2n) of diploid plants and the mitotically arrested generative cell (2n) of the bicellular pollen induced by trifluralin treatment was detected by the presence of shriveled kernels on pollinated ears. A covered method (tassels covered with aluminum foil for 24 h after spraying) and a non-covered method were compared, and the non-covered treatment with 0.2-0.4% trefanocide solutions was the most effective treatment in producing viable bicellular pollen. About 40-50% of the kernels were shriveled on pollinated ears from the treatments. Chromosome counts on seedlings obtained from 0.3% non-covered treatment revealed 24% were triploid and 4% were aneuploid (2n = 19, 21, and 22).Key words: aneuploid, bicellular pollen, trifluralin, triploid, Zea mays L.

scholarly journals Effects of phosphorus deficiency on anatomical structures in maize (Zea mays L.)

1970 ◽  
Vol 39 (1) ◽  
pp. 57-60 ◽  
Author(s):  
Bimal Chandra Sarker ◽  
JL Karmoker ◽  
Parveen Rashid
Keyword(s):  
Zea Mays ◽  
Structural Changes ◽  
Zea Mays L ◽  
Vascular System ◽  
Phosphorus Deficiency ◽  
Sand Culture ◽  
Anatomical Structures ◽  
Vascular Area ◽  
Half Strength ◽  
Pericycle Cells

Anatomical response of maize (Zea mays L.) to phosphorus deficiency grown in sand culture and half strength Hoagland solution revealed that phosphorus deficiency caused a decrease in diameter of the root and stem as well as thickness of the leaf. Epidermal cells of the root, stem and leaf became thickened, cortical zone of root and stem was reduced, endodermal and pericycle cells became smaller and thick walled in phosphorus deficient plants. The prominent structural changes due to phosphorus deficiency occurred in the vascular system where the vascular area is decreased with less number of xylem vessels and smaller size of the cavity. Phosphorus deficiency also resulted in decreased number and smaller sized stomata in leaves. Key words: Phosphorus deficiency; Anatomy; Maize; Zea mays L. DOI: 10.3329/bjb.v39i1.5527Bangladesh J. Bot. 39(1): 57-60, 2010 (June)

Late steps of egg cell differentiation are accelerated by pollination in Zea mays L.

Planta ◽  
2000 ◽  
Vol 210 (5) ◽  
pp. 749-757 ◽  
Author(s):  
Rafał Mól ◽  
Krystyna Idzikowska ◽  
Christian Dumas ◽  
Elisabeth Matthys-Rochon
Keyword(s):  
Zea Mays ◽  
Cell Differentiation ◽  
Zea Mays L ◽  
Egg Cell

Ultrastructural observations of the mature megagametophyte and the fertilization in wheat (Triticum aestivum)

1985 ◽  
Vol 63 (2) ◽  
pp. 163-178 ◽  
Author(s):  
Ruilin You ◽  
William A. Jensen
Keyword(s):  
Triticum Aestivum ◽  
Pollen Tube ◽  
Cell Walls ◽  
Embryo Sac ◽  
Mature Embryo ◽  
Central Cell ◽  
The Other ◽  
Egg Cell ◽  
Filiform Apparatus ◽  
Egg Apparatus

The mature embryo sac of wheat contains an egg apparatus composed of an egg cell and two synergids at the micropylar end, a central cell with two large polar nuclei in the middle, and a mass of 20 to 30 antipodals at the chalazal end. A comparison was made of the ultrastructural features of the various cells of the embryo sac. The features included the position of the nucleus and vacuoles, the number, structure, and distribution of organelles, and the extent of the cell walls surrounding each cell. The pollen tube enters one synergid through the filiform apparatus from the micropyle. The penetration and discharge of the pollen tube causes the further degeneration of that synergid, which had already undergone changes before pollination. The second synergid does not change further in appearance following the penetration of the first by the pollen-altered tube. Half an hour after pollination at 20–25 °C, two male nuclei are seen in the cytoplasm of the egg and the central cell. At about 1 h after pollination, one sperm has made contact with the egg nucleus, while the other sperm is fusing with one of the polar nuclei.

Endosperm development in Zea mays; implication of gametic imprinting and paternal excess in regulation of transfer layer development

Development ◽  
1995 ◽  
Vol 121 (9) ◽  
pp. 3089-3097 ◽  
Author(s):  
W. L. Charlton ◽  
C. L. Keen ◽  
C. Merriman ◽  
P. Lynch ◽  
A. J. Greenland ◽  
...  
Keyword(s):  
Zea Mays ◽  
Sperm Nucleus ◽  
Endosperm Development ◽  
Central Cell ◽  
Egg Cell ◽  
Cell Nuclei ◽  
Transfer Layer ◽  
Sperm Nuclei ◽  
Gametic Imprinting ◽  
Layer Development

Fertilisation in maize (Zea mays), in common with most angiosperms, involves two fusion events: one of the two sperm nuclei unites with the egg cell nucleus, while the other sperm nucleus fuses with the two central cell nuclei giving rise to the triploid endosperm. Since deviation from this nuclear ratio (2:1 maternal/paternal) in the endosperm can result in abortion, it has been suggested that the genomes of the sperm and/or central cell are differentially imprinted during sexual development. By crossing a normal diploid maize line as female with its autotetraploid counterpart, an unbalanced genomic ratio (2:2 maternal/paternal) is created in the endosperm which often results in the eventual abortion of the tissue. Detailed structural comparison of these aberrant endosperms with normal endosperms reveals that the formation of the transfer cell layer, a tissue formed some 8 days after pollination and responsible for the transport of nutrients into the endosperm, is almost completely suppressed under conditions of paternal genomic excess. The first structural analysis of the development of this tissue in normal and aberrant endosperms is reported, and the implications of regulating the formation of such a tissue by gametically imprinted genes are discussed in the light of current theories on the consequences of genomic imbalance on early embryonic development.

Silicon Effects on Metal Tolerance and Structural Changes in Maize (Zea mays L.) Grown on a Cadmium and Zinc Enriched Soil

2008 ◽  
Vol 197 (1-4) ◽  
pp. 323-330 ◽  
Author(s):  
Karina Patrícia Vieira da Cunha ◽  
Clístenes Williams Araújo do Nascimento
Keyword(s):  
Zea Mays ◽  
Structural Changes ◽  
Zea Mays L ◽  
Metal Tolerance

Ultrastructural studies on the embryo sac of Viscum minimum: II. Megagametogenesis

1994 ◽  
Vol 72 (11) ◽  
pp. 1613-1628 ◽  
Author(s):  
M. Zaki ◽  
J. Kuijt
Keyword(s):  
Early Stage ◽  
Light And Electron Microscopy ◽  
Embryo Sac ◽  
Mature Embryo ◽  
Mitotic Division ◽  
Central Cell ◽  
Egg Cell ◽  
Ultrastructural Studies ◽  
Stage Of Development ◽  
Final Length

Embryo sac development of Viscum minimum was investigated using light and electron microscopy. Stages described involve uninucleate, binucleate, four-nucleate, and mature embryo sacs following cellularization. During the early stage of development, prior to mitosis, numerous small vacuoles are initiated in the cytoplasm of a uninucleate functional megaspore. The centrally located nucleus undergoes the first mitotic division and results in formation of two identical nuclei sharing a common cytoplasm. As the vacuole increases rapidly in size, the two nuclei become separated and move to opposite poles where the second mitotic division takes place. A remarkable elongation of the embryo sac is observed between the second and third mitotic division. Eventually, the embryo sac reaches its final length, two-thirds of the length of the ovary, at cellularization. Elongation of the embryo sac is closely related to the increase in vacuole size. Factors involved in vacuole formation and in the elongation of the embryo sac are discussed along with changes accompanying the transition from a sporophytic to a gametophytic pattern of development. Ultrastructural studies on the mature embryo sac, following cellularization, suggest that the egg cell is the least active cell in the megagametophyte. On the other hand, the synergids appear metabolically very active, being rich in plastids, mitochondria, dictyosomes, numerous vesicles, polysomes, and reserves. The central cell is the largest cell in the embryo sac. In a mature embryo sac the central cell has two adjacent nuclei, suggesting that fusion of the nuclei is completed following pollination and fertilization. The antipodals possess a complete set of organelles, numerous free and aggregated ribosomes, and endoplasmic reticulum. It is believed the antipodals play a significant nutritive role during the development of the embryo sac of V. minimum. Modification of the wall between antipodals and central cell and its role in nutrient transportations are discussed. Key words: embryo sac, embryogenesis, gametogenesis, megagametogenesis, mistletoes, ultrastructure.

Sign in / Sign up

Export Citation Format

Share Document