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

Why iodine is vital for human beings, Q. Why iodine is vital for human bein...

Q. Why iodine is vital for human beings? Iodine is a essential chemical element for the proper functioning of the thyroid since it is part of the hormones produced by this glan

Lungs - respiratory organs, Lungs - Respiratory Organs In arachnid art...

Lungs - Respiratory Organs In arachnid arthropods such as scorpion and spider, respiration takes place by means of book lungs. There are four pairs of these structures in the

What are mitochondria, Mitochondria are the organelles in which the most si...

Mitochondria are the organelles in which the most significant part of the cellular respiration happens: the ATP production.

Crab, What are the excretory organs of crab

What are the excretory organs of crab

What is coarctation of aorta, What is Coarctation of Aorta ? More commo...

What is Coarctation of Aorta ? More common in males (3:l). Narrowing of aorta typically located near aortic attachment of ligamenturn arteriosum or PDA. It can be a localized

What is cell theory, What is cell theory? Cell theory declares that the...

What is cell theory? Cell theory declares that the cell is the constituent unit of living beings. Before the discovery of the cell, it was not identified that living beings

Viruses, are viruses cellular organisms

are viruses cellular organisms

Cycles of matter, describe the path of nitrogen through its biogenochemicsa...

describe the path of nitrogen through its biogenochemicsal cycle

Explain about the micronutrient deficiencies, Explain about the Micronutrie...

Explain about the Micronutrient Deficiencies? Micronutrient deficiencies are more common during calamities. Can you guess, why? This is due to the lack of diversified food item

Induction of antimicrobial substances, Induction of antimicrobial substance...

Induction of antimicrobial substances Phytoalexins are antimicrobial substances produced by plants in response to pathogen. They accumulate at the site of infection. For exam

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