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

Pneumonia, Pneumonia Pneumonia is an inflammatory process in which th...

Pneumonia Pneumonia is an inflammatory process in which there is consolidation in lung caused by exudates filing the alveolar spaces. Gas exchange cannot take place in the c

Ecosystem control, Ecosystem Control Another important aspect of ecosy...

Ecosystem Control Another important aspect of ecosystem functioning that is how it maintains its ecological balance. By now, it must be obvious to you that an ecosystem is a d

What is kingdom plantae or how organism included in plantae, What is Kingdo...

What is Kingdom Plantae and what organism included in Plantae? Kingdom Plantae :  includes organisms that are eukaryotic, multicellular, photosynthetic. Their cells also cont

Are nematodes triploblastic or diploblastic animals, Q. Are nematodes tripl...

Q. Are nematodes triploblastic or diploblastic animals? Just like platyhelminthes, nematodes are triploblastics that is they present three germ layers (ectoderm, endoderm and m

What is short acting insulin, Q. What is Short acting insulin? Short ac...

Q. What is Short acting insulin? Short acting: This type of insulin begins working quickly, works hardest 2- 3 hours after injection but is completely gone after 4-6 hrs. So if

What are the differences between minerals and ores , Menerals are naturally...

Menerals are naturally occurring inorganic solids with a crystalline structure and a definite range of chemical formula. Ores are concentrations of minerals in rock.

Zoogly, are protozoans primitive to life .

are protozoans primitive to life .

Can you explain the anoxia, Q. What is the anoxia? Anoxia is a situatio...

Q. What is the anoxia? Anoxia is a situation in which there is no available oxygen in the cell without oxygen the respiratory chain stops there is no ATP production the cell do

Importance of pituitary gland, Importance of pituitary gland Pitutar...

Importance of pituitary gland Pitutary gland is very small and it is about the size of a large pea seed. It is very important as it controls the functions of all the othe

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