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 is striped pattern of the striated muscle cells formed, How is the stri...

How is the striped pattern of the striated muscle cells formed? The functional units of the muscle fibers are the sarcomeres. Within the sarcomeres blocks of myosin and actin

Stress testing after myocardial infraction, Q. Stress Testing after Myocard...

Q. Stress Testing after Myocardial Infraction? Many post infarction deaths are sudden and occur with in the first 6 months after infarction. Exercise testing from 10 days to we

Molluscus - hormones in growth and reproduction, Molluscus - Hormones in Gr...

Molluscus - Hormones in Growth and Reproduction We know quite well about the endocrine mechanism of growth and reproduction in the freshwater snail Lymnaea stagnalis. This is

Find a chemically gated protein, You have identified a protein in a cell th...

You have identified a protein in a cell that you know that comes from the human body. With respect to that protein you have also determined that it allows sodium ions to go through

How do the golgi apparatus act, Q. How do the Golgi apparatus act and the r...

Q. How do the Golgi apparatus act and the rough endoplasmic reticulum in the production and releasing of proteins? The rough endoplasmic reticulum has in its outer membrane man

What is the difference among systole and diastole, What is the difference a...

What is the difference among systole and diastole Systole and diastole are the two stages into which the cardiac cycle is separated. Systole is the stage when the contraction o

Proteins of animal origin - fish, Proteins of Animal Origin - Fish Fish...

Proteins of Animal Origin - Fish Fish: The edible portion is skeletal muscles of the body. Even though the skeletal muscles of different animals are basically similar, fish spe

Which are the plant tissues, Which are the plant tissues responsible for th...

Which are the plant tissues responsible for the supporting of the plant? The plant supporting tissues are the collenchyma and the sclerenchyma. The collenchyma is made of li

Water relations in terrestrial environment, Water Relations in Terrestrial ...

Water Relations in Terrestrial Environment Insects are the largest group of metazoans which have most successfully invaded the terrestrial environment. In addition, most arach

Write the meaning of diabetes mellitus, Q. Write the meaning of diabetes me...

Q. Write the meaning of diabetes mellitus? The word "diabetes" is from the Greek word meaning "a siphon". Diabetes patients had polyuria (passing excessive urine) and "pass it

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