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

Explain the role of cuvier in animal taxonomy, Explain the role of cuvier i...

Explain the role of cuvier in animal taxonomy? Cuvier (1769-1832) was critical of Lamarck's evolutionary concept which thereafter remained in oblivion for half a century. Cuvi

What are the grain boundaries, What are the Grain boundaries Grain boun...

What are the Grain boundaries Grain boundaries disrupt the motion of dislocations by a material, so reducing crystallite size is a common way to improve strength. Since grain b

Explain adverse effects of ribavirin, Adverse Effects of Ribavirin  Sys...

Adverse Effects of Ribavirin  Systemic ribavirin has been associated with hemolytic anemia. Oral ribavirin plus interferon appears to cause a higher incidence of cough, pruritu

Explain about the derived proteins, Explain about the Derived Proteins? ...

Explain about the Derived Proteins? These are not naturally taking place proteins and are obtained from simple proteins by the action of enzymes and chemical agents, heat, mech

Explain about the ascomycota - fungi, Explain about the Ascomycota - Fungi?...

Explain about the Ascomycota - Fungi? Ascomycota - Ascomycetes or sac-like fungi have septate mycelium. These are called so because sexual reproduction involves the formation o

State about charles elton, What evidence did Charles Elton collect that sug...

What evidence did Charles Elton collect that suggested that fluctuations in hare and lynx populations were related? What other evidence shows that these fluctuations ma

Define iron requirements of infants, Define Iron requirements of infants? ...

Define Iron requirements of infants? The maintenance needs for all age groups is 14 mcg/kg body weights. For infants and preschoolers, iron needs for growth and' expansion of b

Write out electronic configuration, Give number of valence electrons for te...

Give number of valence electrons for technetium. Write out electronic configuration for the valence electrons. Give the number of valence electrons and the number of electronic con

What is a burette and how is it used, What is a burette and how is it used?...

What is a burette and how is it used? A burette is a uniform-bore glass tube with fine gradations and a stopcock at the bottom, used particularly in laboratory procedures for a

Main means by which autotrophic beings obtain energy, What is the main mean...

What is the main means by which autotrophic beings obtain energy? The major means by which autotrophs obtain energy is photosynthesis (There are also chemosynthetic autotrophs)

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