Polygonum type - monosporic embryo sacs, Biology

Assignment Help:

Polygonum Type - Monosporic Embryo Sacs

The embryo sac is formed from the chalazal megaspore in the tetrad and is eight-nucleate. The development of the embryo sac begins with elongation of the functional megaspore. Initially, the megaspore cytoplasm is non-vacuolated but later small vacuoles appear which fuse to form a large vacuole. The spindle of the nuclear division in the megaspore is oriented along the long axis of the cell. Wall is not formed after the nucleus divides.

A large central vacuole appears between the two daughter nuclei. It expands and pushes the nuclei towards the opposite poles of the cell. Both the nuclei divide to form four nuclei, two at each pole. By a further division an eight nucleate condition is reached. This is followed by cellular organisation of the embryo sac. Out of the four nuclei at the micropylar end of the sac, three organize into egg apparatus and the fourth is left free in the cytoplasm of the central cell as the upper polar nucleus. Similarly, three nuclei of the chalazal quartet form three antipodal cells; the fourth one functions as the lower polar nucleus. Eventually, the latter comes to lie close to the upper polar nucleus.


Related Discussions:- Polygonum type - monosporic embryo sacs

Explain the membrane equilibria, Explain the Membrane Equilibria? A sem...

Explain the Membrane Equilibria? A semipermeable membrane used to separate two liquid phases can, in principle, be permeable to certain species and impermeable to others. A mem

Define the cooper''s run (12 minute run) method, Define the Cooper's Run (1...

Define the Cooper's Run (12 minute run) Method? To undertake this test, a 400 metre running track is required-marked every 100 m and a stop watch. The test comprises of noticin

On site sanitation, Introduction: There are different technologies avai...

Introduction: There are different technologies available for dealing with waste water management and excreta.  Some are suitable for dealing off-site sanitation and other can b

Is geometric isomers have the same connectivity, Geometric isomers: Select ...

Geometric isomers: Select one: a. Have the same molecular weight b. Have the same connectivity c. Have a different configuration about a double bond d. All of the above

Illustrate about the intra-ocular pressure, Illustrate about the Intra-ocul...

Illustrate about the Intra-ocular pressure It is the pressure maintained inside the eye above the atmospheric pressure. It is higher than fluid pressure in any other tissue (2-

Describe prematurity in coronaw artery disease, Describe Prematurity in cor...

Describe Prematurity in coronaw artery disease ? CAD in Indians tends to be more aggressive and manifests at a younger age. Generally CAD occurring before the age of 55 years i

Drawbacks of lamellar model, Drawbacks of Lamellar model This model ...

Drawbacks of Lamellar model This model does not explain the elasticity of PM. Although this model says that PM is elastic but it also states that head of lipid molecules is

Explain enzyme glutamate oxaloacetate, Enzyme  glutamate oxaloacetate tran...

Enzyme  glutamate oxaloacetate transaminase catalyzes  the  reaction between glutamate and oxaloacetate with the formation of a-ketoglutarate and aspartate due to transfer  of one

Objectives of gingival curettage - endodontic surgery, Objectives of Gingiv...

Objectives of Gingival Curettage - Endodontic Surgery a) Provides access and visibility of the apex, b) Removal inflamed tissues, c) Provides biopsy. -  It’s advisable

Molecular biology, how biochemical evidence proof DNA as a genetic material...

how biochemical evidence proof DNA as a genetic material?

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