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

Theory of epigenesis - pre-mendelian theory, Theor y of Epigenesis (i)...

Theor y of Epigenesis (i)          It was proposed by C.F. Wolff & supported by Von Baer. (ii)         Wolff proposed that germ cells contain definite but undifferentiated

Diversity is good axioms of conservation biology, "Diversity is good" is on...

"Diversity is good" is one of the axioms of conservation biology. However in absentia of historical information, why is noting higher diversity in a system NOT the best way to eval

Determine the concept of digestion of fats, Which of the following assist i...

Which of the following assist in the digestion of fats? A. Production of bile salts in the liver and the secretion of those bile salts into the small intestine. B. Emulsific

Renal function & cardiovascular - change related with ageing, Define Renal ...

Define Renal Function & cardiovascular - change related with ageing? Changes associated with the cardiovascular and renal function: The progressive accumulation of athermanous

What is the location of the salivary glands in humans, What is the location...

What is the location of the salivary glands in humans? There are 6 major salivary glands and they are located one in every parotid gland, two beneath the mandibles (submandibul

What are the factors which influence the spoilage of meat, Q. What are the ...

Q. What are the factors which influence the spoilage of meat? Can you list a few? Ans. Sure enough, you should be able to enumerate these having learnt about them earlier

Chordata, what are the two main subdivisions of the phylum chordata

what are the two main subdivisions of the phylum chordata

Research to improve health care delivery, Research to Improve Health Care D...

Research to Improve Health Care Delivery: Today, much  of health  care  delivery  system remains  imitative  and intuitive rather than innovative,  creative or  scientific in

What is the digestive enzyme that acts within the stomach, What is the dige...

What is the digestive enzyme that acts within the stomach? Which type of food does it digest? What are the cells that produce that enzyme? The digestive enzyme that acts in the

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