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

Lab report, Why making a smoke print of a leaf

Why making a smoke print of a leaf

Define methods for determining ph - nutritional biochemistry, Define Method...

Define Methods for determining pH? There are two general methods for determining pH of a solution. One is the colorimetric method and the other most common method is the use of

Symptoms of oesophagitis, Q. Symptoms of oesophagitis? The symptoms of ...

Q. Symptoms of oesophagitis? The symptoms of oesophagitis include heartburn or pyrosis, iron-deficiency anaemia due to chronic tissue bleeding, aspiration, which may cause coug

Cephalopods - feeding and digestion in molluscs, Cephalopods - Feeding and ...

Cephalopods - Feeding and Digestion in Molluscs Cephalopods are carnivorous. Tentacles or arms are food capturing organs. The number of tentacles changes in different cephalop

What is genes duplication, What is genes Duplication ? Duplication of g...

What is genes Duplication ? Duplication of genes can happen when a portion of a chromosome breaks off and attaches itself to the end of its homologous chromosome, as seen below

Knock-out experiment, Knock-out experiment  is a method for deleting, mutat...

Knock-out experiment  is a method for deleting, mutating or otherwise inactivating the gene in a mouse. This laborious technique involves transfecting a crippled gene into cultured

Pulse oximetry readings, Outline three client considerations when taking an...

Outline three client considerations when taking an accurate pulse oximetry reading.

Define about the growth and development in children, Define about the Growt...

Define about the Growth and development in children? Growth and development in children can be studied under the following heads: . • Changes in physical development and bod

Statistical measures - population, Statistical Measures - Population A...

Statistical Measures - Population A population has a number of group characteristics that are statistical measures unique to the population group and are not the characteristi

Biological adaptation, Biological Adaptation These adaptations depend ...

Biological Adaptation These adaptations depend on the geology and basic fertility of the region and some of the mechanisms that are especially well developed in tropical rain

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