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 sexually-transmitted diseases, Sexually-transmitted diseases M...

Sexually-transmitted diseases Many travelers have new sexual contacts during their journeys and are at increased risk for acquiring sexually transmitted diseases including HIV

Determine some indicators of malnutrition, Determine Some indicators of Mal...

Determine Some indicators of Malnutrition? A few of the indicators are enumerated below: 1. Indicators related to Government policies a. Nutrition policy b. Nutrition

What is mucic acid test and its principle, What is Mucic Acid Test and its ...

What is Mucic Acid Test and its principle? This is a specific test for galactose and is given by galactose as well as lactose, which is made up of galactose and glucose. Pr

Explain susceptible organisms of tubeculosis, Susceptible Organisms Wh...

Susceptible Organisms When infection proves to be caused by a fully susceptible strain of TB, the initial phase of treatment should include isoniazid, rifampin and pyrazinamid

Explain directly observed therapy of tuberculosis, Directly observed therap...

Directly observed therapy In treating TB, poor adherence to therapy is the most important cause of treatment failure and is associated with emergence of drug resistance. Medica

Determine effective half life and value of effective decay, 1. By direct me...

1. By direct measurement of the activity of the thyroid gland in several patients who had received 131 I for diagnostic purposes, it was observed that the biological elimination h

Clostridium botulinum, Clostridium botulinum is an anaerobic, Gram-positive...

Clostridium botulinum is an anaerobic, Gram-positive, spore forming, rod shaped bacteria that produces the potent neurotoxin. The organism and its spores are widely distributed in

Define role in protein metabolism and growth, Define Role in protein metabo...

Define Role in protein metabolism and growth? Severe vitamin A deficiency results in abnormal RNA metabolism and protein synthesis and hence interferes with growth. Hence vitam

EMBRYONIC PERIOD, LIST OUT THE DERIVATIVES OF 3 GERMS LAYER-ectoderm, meso...

LIST OUT THE DERIVATIVES OF 3 GERMS LAYER-ectoderm, mesoderm and endoderm

How do arthropods grow, Q. How do arthropods grow? Due to the presence ...

Q. How do arthropods grow? Due to the presence of exoskeleton the growth of an arthropod is periodical during the growth period the animal loses the exoskeleton, develops and g

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