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

Describe the need for harmonization in clinical trials, Question 1: Des...

Question 1: Describe the need for Harmonization in clinical trials? Brief on the Revised ICH terms of reference and explain the structure of ICH? Need for Harmonization i

Inheritence, What is inheritence and what is the relation between mendel an...

What is inheritence and what is the relation between mendel and darwin?

How buffer solution can be prepared, How Buffer Solution Can Be Prepared? ...

How Buffer Solution Can Be Prepared? A buffer solution can be prepared to have a desired value of pH by controlling the amount of acid and its salt in case of acidic buffer and

Explain the nasopalatine nerve and vessels, Nasopalatine nerve and vessels ...

Nasopalatine nerve and vessels Found in the nasopalatine canal, must be taken care off when placing implants in the maxillary incisor region. Subperiosteal implant placement o

What is the advantage of the occurrence of larval stage, Q. What is the evo...

Q. What is the evolutionary advantage of the occurrence of larval stage and sperm cells in the life cycle of sponges? The sexual reproduction in sponges in addition to contribu

Agro industrial-animal wastes, Animal wastes Large quantities of anima...

Animal wastes Large quantities of animal wastes are available in the country but generally they are low in nutrient content with poor feeding value to the animals. However, po

Major divisions of the chordate phylum, Q. What are the two major divisions...

Q. What are the two major divisions of the chordate phylum? Chordates are divided into vertebrates and protochordates (urochordates and cephalochordates). Q. What are the d

Conditioned reflex , CONDITIONE D REFLEX - Response which is achiev...

CONDITIONE D REFLEX - Response which is achieved by training is conditioned reflex. I. P. Pavlov in 1920 displayed it by experimenting on dog. These are voluntary in

Sedentary or light activity lifestyles - physical activity, How Sedentary o...

How Sedentary or light activity lifestyles affects Physical Activity? These people have occupations that do not demand much physical effort, we not required to walk long distan

Determine the food sources of folate, Determine the Food Sources of Folate?...

Determine the Food Sources of Folate? Folate occurs naturally in foods. Although folate is found in a wide variety of foods, it is present in a relatively low density except i

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