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

Wind as a medium for dispersal, Wind as a medium for Dispersal Many mic...

Wind as a medium for Dispersal Many microorganisms, fungal spores and bacteria are freely transported over long distances even by moderate winds. In wind pollinated plants, the

Define non-digestible oligosaccharides (ndo), Define Non-Digestible Oligosa...

Define Non-Digestible Oligosaccharides (NDO) Among the various food components, the best prebiotic effects seen to be exerted by the NDOs. They are oligomeric carbohydrates, wh

Operative requirements for stage i surgery, Operative requirements for stag...

Operative requirements for stage i surgery Although Implant placement under general anesthesia must be done in an operating theatre with complete resources, most implant surger

What are the main risk factors for hypertension, Q. What are the main risk ...

Q. What are the main risk factors for hypertension? The major risks factors for hypertension are tobacco smoking, stress, obesity, sedentary lifestyle and alcoholism.

What are the main classes into which the phylum is divided, What are the ma...

What are the main classes into which the phylum is divided? What are some examples of each and in which form (polyp or medusae) are they found? Coelenterates are separated into

Division phase or mitosis, DIVISION PHASE OR MITOSIS (M- PHASE) Cell di...

DIVISION PHASE OR MITOSIS (M- PHASE) Cell division was first  observed by  Naegeli 1842 in plant cells ,but  thoroughly described by Eduard strasburger  1875. Fleming 1879 desc

Mucoproteins (glycoproteins), MUCOPROTEIN S (GLYCOPROTEINS) Protein...

MUCOPROTEIN S (GLYCOPROTEINS) Proteins having conjugated mucosaccharides that form viscous mucus or mucoid secretions. The gastric mucus or mucoprotein is resistant to p

Determine the sodium-potassium atpase pumps, A normal healthy cell is bathe...

A normal healthy cell is bathed in a normal extracellular saline.  The plasma membrane of the cell contains voltage-gated sodium channels, sodium-glucose co-transporters, and sodiu

Can you define p-waves, Q. Can you define P-Waves? Changes in P-wave mo...

Q. Can you define P-Waves? Changes in P-wave morphology have been well described in resting tracings and are very useful in identifying right and left sided hemodynamic alterat

What is the constitutional unit of proteins, What is the constitutional uni...

What is the constitutional unit of proteins? The constitutional units of proteins are the amino acids. Protein Structure Review - a) Image Diversity b) amino acid stru

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