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

Probability concept of requirements vs risk of deficient, Define Probabilit...

Define Probability concept of requirements vs risk of deficient and excess intake? Figure best illustrates the concept of a requirement for an essential nutrient. The relations

How can the blood coagulation process be described, How can the blood coagu...

How can the blood coagulation (clotting) process be described? Blood clotting encompasses a sequence of chemical reactions whose respective products are enzymes that catalyze t

Explain law of the transmission of acquired characteristics, What is meant ...

What is meant by the law of use and disuse and by the law of the transmission of acquired characteristics? According to the law of use and disuse the characteristics of a body

Community-based health insurance systems, Normal 0 false fals...

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

How a sample contaiinng this isotope decay, Please help with the following:...

Please help with the following: 32P is an unstable isotope of phosphorus that has a half-life of 14.29 days. Atoms of this isotope undergo beta decay in which a neutron decays i

Role of wound epidermis and apical epidermal cap, Role of Wound Epidermis a...

Role of Wound Epidermis and Apical Epidermal Cap Earlier described that amputation, the stump epidermal cells at the wound edge migrate over and quickly cover the wound to fro

Consequences of shifting the chemical equilibrium, Q. What are the conseque...

Q. What are the consequences of shifting the chemical equilibrium of the formation of bicarbonate from carbon dioxide and water towards the increase of product (bicarbonate) format

Explain gluconeogenesis, Explain Gluconeogenesis Gluconeogenesis (i.e...

Explain Gluconeogenesis Gluconeogenesis (i.e synthesis of  new  glucose)  is  the  synthesis of carbohydrate from  non-carbohydrate, source. The major  substrates for glucone

Tissue culture, Note on production of haploid by tissue culture.

Note on production of haploid by tissue culture.

Excretory organs, The excretory organs and excretory materials of plants an...

The excretory organs and excretory materials of plants and animals

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