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

How old is the universe, How old is the universe? From the analysis of ...

How old is the universe? From the analysis of data collected by the Hubble telescope the age of the universe is estimated to be about 12 billion years.

Describe the the growth of the plants in the 2 groups, There has not been r...

There has not been rain for several months. A biologist is driving down the highway and notices that a large number of corn fields have corn that is wilted and short. She wonders i

Define the roller drying (drum drying) method, Define the Roller Drying (Dr...

Define the Roller Drying (Drum drying) Method? One of the important techniques for drying liquid food products is the roller drier. Like spray drying, roller drying can only be

How to recognition of congenital heart disease, How to Recognition of Conge...

How to Recognition of Congenital Heart Disease ? The manifestations of CE-ID are different in a neonate, an infant or a child. It is often easy to recognise the presence of CHD

Define the postsynaptic potential in neuron a, Neuron A is a healthy neuron...

Neuron A is a healthy neuron with all the usual ion channels.  When at rest with a membrane voltage of R millivolts, neuron A produces no action potentials.  The voltage thres

Control of gene expression, explain the relationship between the terms.. In...

explain the relationship between the terms.. Inducer,activation transcription factor,enhancer

What is cellular grade. explain in brief., What is Cellular grade? Explain ...

What is Cellular grade? Explain in brief. Organisms with this kind of cellular organization are referred to as the parazoan. They have distinct cells which function independent

Explain about the spectrophotometer, Explain about the Spectrophotometer? ...

Explain about the Spectrophotometer? The spectrophotometer, a key instrument today in biomedical laboratories, was invented in 1939 by the American chemist Arnold O. Beckman (1

Explain brachial or radial approach, Q. Explain Brachial or Radial Approach...

Q. Explain Brachial or Radial Approach ? This technique involves performing the coronary angiogram through the right brachial artery in the right ante-cubital fossa. Usually a

Define hormonal and receptor proteins, Define Hormonal and Receptor Protein...

Define Hormonal and Receptor Proteins? Hormonal proteins : Hormonal proteins coordinate the bodily activities. Several peptide and protein hormones (like insulin and growth ho

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