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

Assortment, Assortment is a method in which the meiosis produces new combi...

Assortment is a method in which the meiosis produces new combinations of the genetic information. The paternal and maternal chromosomes line up randomly during the process of syna

Blood pressure, An adequate level of pressure is needed in the arteries to ...

An adequate level of pressure is needed in the arteries to keep the blood flowing through the cardiovascular system. The chief determinant of arterial pressure is the volume of blo

Determine the excitation threshold concerning neurons, How different are th...

How different are the concepts of action potential, resting potential and excitation threshold concerning neurons? Action potential is the maximum positive voltage level achiev

Define about the spectral techniques - colorimetry, Define about the Spectr...

Define about the Spectral Techniques - Colorimetry? Many determinations in the biochemistry laboratory are based on measurements of radiant energy emitted, transmitted, absorbe

Production diseases, Pr o d u c t i o n Diseases The production...

Pr o d u c t i o n Diseases The production diseases, which were previously referred as metabolic diseases, include diseases like parturient paresis (milk fever), downer

Explain about the osteomalacia - deficiency of vitamin d, Explain about the...

Explain about the Osteomalacia - Deficiency of Vitamin D? It occurs when there is a lack of vitamin D and calcium, in women who have had many pregnancies, who subsist on a meag

Show takhtajans system of classification, Q. Show Takhtajans System of Clas...

Q. Show Takhtajans System of Classification? Another important phytogenetic system was proposed by Takhtajan, the famous Russian Palaeobotanist working at Komarov Botanical Ins

What is the original concentration, A sample of yeast cells was serially di...

A sample of yeast cells was serially diluted 1/10 five times then serially diluted 1/3. the number of yeasts was338 yeasts per ml. what was the original concentration? Please show

Scope of user charges, Normal 0 false false false EN-IN...

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

Cell division., sir i''m not understanding cell division rightly. in ca...

sir i''m not understanding cell division rightly. in case of meiosis both paternal and maternal chromosome goes in two cell separately while in case of mitosis they go alongwit

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