Tetrasporic embryo sacs, Biology

Assignment Help:

Tetrasporic Embryo Sacs

In this group neither of the meiotic divisions is accompanied by wall formation so that at the end of meiosis all the four haploid nuclei remain in a common cytoplasm forming what is termed a coenomegaspore. A tetrasporic embryo sac is more heterogeneous than a bisporic embryo sac because the four products of meiosis involved in its formation are genetically different. The nuclear behavior in tetrasporic embryo sacs is quite variable. The arrangement of the four nuclei in the coenomegaspore before the beginning of post-meiotic mitosis is of three types:

(A) 2+2 arrangement; two nuclei at the micropylar ad and two of the chalazal end

 (B) 1+1+1+1 arrangement; one nucleus at the micropylar end, one at the chalazal end, and two placed laterally, one in each side, and

(C) 1+3 arrangement; one nucleus at the micropylar end and three at the chalazal end. Depending on whether nuclear fusion occurs or not, the number of the post-meiotic mitosis in the coenomegaspore and final organisation of the embryo sac, tetrasporic embryo sacs are of many types.


Related Discussions:- Tetrasporic embryo sacs

Conditioned reflex , CONDITIONE D REFLEX - Response which is achiev...

CONDITIONE D REFLEX - Response which is achieved by training is conditioned reflex. I. P. Pavlov in 1920 displayed it by experimenting on dog. These are voluntary in

Explain in detail about male reproductive system, Explain in detail about M...

Explain in detail about Male Reproductive System The male reproductive organ consists of the following:  A pair of testes, held in scortum; produces spermatooa and testoster

Veterbrate, Draw and describe the structure of amphibian,reptile mammal and...

Draw and describe the structure of amphibian,reptile mammal and bird

Tail - structure of the sperm, Tail - Structure of the Sperm The tail ...

Tail - Structure of the Sperm The tail or flagellum is the longest part of the sperm. By its movement it causes the sperm to swim with the head forward. It consists of a thin

What is class crinoidea, What is Class Crinoidea? This Class includes t...

What is Class Crinoidea? This Class includes the sea lilies and the feather stars. What makes them different from the other Echinoderms is the placement of their mouth and anus

Newton, meaning of the law of inertia

meaning of the law of inertia

What is plutonium reprocessing, Q. What is plutonium reprocessing? Why is i...

Q. What is plutonium reprocessing? Why is it a big environmental issue? The Plutonium is the highly radioactive chemical element produced from uranium by nuclear plants. The Pl

Food intoxications, Food borne intoxications are basically food borne illne...

Food borne intoxications are basically food borne illness caused due to ingestion of toxin produced my microorganisms (mycotoxins, bacterial toxins). Natural toxins present in food

Explain composition of amino acid, Explain amino acid composition In te...

Explain amino acid composition In terms of amino acid composition, high radiation doses such as those required for sterilization (e.g. 25-27Kgy), do not change the content of c

Bronchial asthma, Bronchial asthma: Bronchial asthma is characterised ...

Bronchial asthma: Bronchial asthma is characterised by bouts of  dyspnoea as a result of  temporary narrowing of bronchi due to bronchial spasm, mucosal edema and thick secret

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