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 are the inheritance patterns of the rh blood system, What are the inhe...

What are the inheritance and dominance patterns of the Rh blood system? The inheritance pattern of the Rh blood system is autosomal dominant, i.e., the heterozygous manifests a

Human reproduction, Why is the human placenta referred to as haemochorial t...

Why is the human placenta referred to as haemochorial type? Name the hormone it secretes to facilitate parturition.

Cell theory, Cell theory is one of the four (or five) unifying concepts in...

Cell theory is one of the four (or five) unifying concepts in the biology. The cell theory states that all the living things are composed of at least one cell and that cell is the

Name the three types of joints in human skeleton, Describe giving one examp...

Describe giving one example of each, the three types of joints in human skeleton, based on the capacity of movement. A patient was complaining of frequent urination, excessive

How is digestion performed in protozoans, How is digestion performed in pro...

How is digestion performed in protozoans? Digestion in protozoans is intracellular digestion: organic material is internalized and degraded inside the cell. Protozoans get

Dietary recommendations proposed by whom, Q. Dietary recommendations propos...

Q. Dietary recommendations proposed by WHOM? We learnt about their etiological factors, metabolic alterations, clinical anifestations and dietary management of the disease of h

Peroxisome and lysosome, e use itwhat is difference between peroxisme and l...

e use itwhat is difference between peroxisme and lysosome what is function of it and where w

Choice of graft material depends on, Choice of graft material depends on ...

Choice of graft material depends on - Its nature towards bone e.g., Osteoconductive or osteoinductive - Its architecture i.e., granular or block, pore si-e - Its origin -

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