Female gametophyte, Biology

Assignment Help:

Female Gametophyte

The development of a female gametophyte is initiated with the enlargement of one of the megaspores (usually the one close to the chalaza in a linear tetrad) followed by three mitotic divisions. Thus, the female gametophyte, also called the embryo sac is almost always a 7-celled or 8-nucleate structure. The eight nuclei thus formed organize into the egg apparatus, central cell with two polar nuclei and three antipodal cells. This mode of embryo sac development occurs in the majority of flowering plants.

There are variations from this mode of female gametophyte development. In order to visualize these deviations let us recall the formation of megaspore tetrad. Out of the four megaspores, three degenerate and only one participates in the formation of embryo sac. This mode of development of female gametophyte is known as the monosporic type. In some plants, two megaspores out of four participate. For example, if after meiosis, the lower or the upper dyad produces the embryo sac and the other degenerates, the development is termed bisporic. Sometimes, cell plate formation does not occur after any of the meiotic divisions and all the four megaspore nuclei contribute to embryo sac formation. 'This is called tetrasporic type of development. Depending upon the orientation and subsequent behavior of the megaspore nuclei and their derivatives, the tetrasporic gametophyte may be of several types.


Related Discussions:- Female gametophyte

What is the defense mechanism to stop an infection, What is the defense mec...

What is the defense mechanism that begins to work when inflammation fails to stop an infection? If the inflammatory attack is not enough to halt the infectious process the body

History of cell biology, HISTORY OF CELL BIOLOGY Scientific knowledge gro...

HISTORY OF CELL BIOLOGY Scientific knowledge grows with the development of new tools and techniques for studying various physical and biological processes. This is true also of t

Attempted suicide - psychiatric emergencies, Attempted Suicide: Suicid...

Attempted Suicide: Suicide and homicide represent major source of morbidity and mortality in psychiatric practice.  Suicide means killing of  oneself.  An attempted suicide is

Explain clostriduim botulinum, Q. Explain Clostriduim botulinum? Clostr...

Q. Explain Clostriduim botulinum? Clostriduim botulinum is widely distributed in soil and marine sediments throughout the. world. It is also found in the intestinal tract of a

What are atherosclerosis, Atherosclerosis, the most common part of hardenin...

Atherosclerosis, the most common part of hardening of the arteries, is characterized by the presence of cholesterol-rich arterial thickenings (atheromas).  This progressive  diseas

Grow Ligth Colors, What colors of light are needed in a grow light for stra...

What colors of light are needed in a grow light for strawberry development?

What are the main features of the meristematic cells, What are the main fea...

What are the main features of the meristematic cells? Why do these cells require to have a high mitotic rate? Meristematic cells have very thin cell walls, small vacuoles, a w

Chromosomes, Chromosomes  are the condensed, fibrillar, self- replicating g...

Chromosomes  are the condensed, fibrillar, self- replicating genetic structures of cells containing the cellular DNA which bears in its nucleotide sequence the linear array of gene

Speciation, SPECIATION - Origin of new species: An isolated popula...

SPECIATION - Origin of new species: An isolated population of a species independently develops different types of mutations. The later accumulate in its gene pool. Afte

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd