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

Explain about the supply curve or supply schedule, Explain about the supply...

Explain about the supply curve or supply schedule. The supply curve or schedule shows the total quantity of a good or a service supplied within aggregate, by whole sellers or f

Determine the genotypes and phenotypes, Determine the genotypes and phenoty...

Determine the genotypes and phenotypes of the F1 generaiton from a colour blind father and a mother who is homozygous for normal colour vision

Closed style - style of stigma interaction, Closed Style - Style of Stigma ...

Closed Style - Style of Stigma Interaction Cotton shows an epidermis with stomata, a cortex of thin-walled parenchyma with several vascular bundles and strands of transmitting

Periapical radiography - criteria for endosteal implants, Q. Periapical rad...

Q. Periapical radiography - criteria for endosteal implants? Periapical radiographs are images of a limited region of the mandibular or maxillary alveolus.  Periapical radiogra

Define changes associated with the skeletal system - ageing, Define Changes...

Define Changes associated with the skeletal system - Ageing? Skeletal bone loss occurs with ageing and may have serious consequences among the elderly. With ageing, there is so

Explain the work of linnaeus in animal taxonomy, Explain the work of Linnae...

Explain the work of Linnaeus in animal Taxonomy? In 18th century, the work of Linnaeus and his followers (Haartman, 1751, 1764, Kolreuter, 1761-66) helped systematic to advance

Mechanism of stomatal opening, Mechanism of Stomatal Opening It has be...

Mechanism of Stomatal Opening It has been known for over a century that stomata open because of reversible turgor changes in the guard cells. Stomata open when turgor in the g

Explain about the dehydration, Explain about the Dehydration? Dehydrati...

Explain about the Dehydration? Dehydration is defined as the excessive loss of body water. It may occur because of inadequate intake, or abnormal loss of body water or a combin

What is oral rehydration therapy, Q. What is Oral Rehydration Therapy? ...

Q. What is Oral Rehydration Therapy? Oral Rehydration Therapy (ORT) refers to providing fluids and/or oral rehydration salt solutions to the patient. An oral rehydration soluti

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