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

Determine the type of bandage, Determine the type of bandage The most com...

Determine the type of bandage The most common type of bandage is the gauze bandage, a simple woven strip of material which comes in different widths and lengths.

Dysrhythmias - complications of cardiac surgery, Dysrhythmias Usually ...

Dysrhythmias Usually occur during the initial 24-72 hours, but may occur later on also. The causes may be ventricular irritability due to manipulations of heart durin

Excretion in non-chordates, Excretion in Non-Chordates Excretion as de...

Excretion in Non-Chordates Excretion as described under Introduction of this unit refers to removal of the waste products of metabolism - carbon dioxide (CO 2 ) and water rele

What is classic blalock-taussig bt shunt in shunt operations, What is Class...

What is Classic Blalock-Taussig BT Shunt in Shunt Operations ? Subclavian artery, which arises from innominate artery, is anastomosed to pulmonary artery. In a patient with lef

What is exudative diarrhoea, Q. What is Exudative diarrhoea? Exudative ...

Q. What is Exudative diarrhoea? Exudative diarrhoea: It is associated with the mucosal damage leading to out pouring of mucus, blood and plasma proteins with a net accumulation

Activation domains, Unlike  DNA  binding  domains  and  dimerization  domai...

Unlike  DNA  binding  domains  and  dimerization  domains,  no  general  structural motifs have since been identified  in the activation  domains  of diverse transcription factors.

Protozoans - regeneration in invertebrates, Protozoans - Regeneration i...

Protozoans - Regeneration in Invertebrates Most single celled animals such as protists, i.e. protozoans, regenerate very well. If part of the cytoplasm is removed from the

Class of subphylum uniramia - insecta, Class of Subphylum Uniramia - Insect...

Class of Subphylum Uniramia - Insecta Class Insecta consists of nearly a million described species. There are more species of insects as compared to all the other species of a

Give the introduction to evaluation of patient clinical, Give the introduct...

Give the introduction to evaluation of patient clinical examination ? A careful physical examinations is a very important for assessing the cardiovascular system and after prov

Why can the genetic code be qualified as a degenerate code, Why can the gen...

Why can the genetic code be qualified as a "degenerate code"? The genetic code is a degenerate code because there are amino acids codified by more than one type of codon. It is

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