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

Nursing assessment - hypospadias, Nursing Assessment Hypospadias can b...

Nursing Assessment Hypospadias can be observed by nurse or parents at birth. The child presents with abnormal pattern of voiding and presence of chordae. The stream of ur

Explain the the lysogenic cycle in diversity of life, Explain the The Lysog...

Explain the The Lysogenic Cycle in diversity of life? The Lysogenic Life History of Bacteriophage Viruses. Even though viruses are structurally simple, consisting of merely a n

Explain the mortality and survivorship curves, Explain the Mortality and Su...

Explain the Mortality and Survivorship Curves? Mortality : Just as a population has a birth rate, so does it have a death rate. A populations rate of death, or the number of

Role of mesoderm and ectoderm in limb morphogenesis, Role of Mesoderm and E...

Role of Mesoderm and Ectoderm in Limb Morphogenesis A series of very interesting experiments on wing and leg buds of chick embryos have clarified the respective roles of meso

What is the plasma membrane of the cell, What is the plasma membrane of the...

What is the plasma membrane of the cell? What are its main functions? The plasma membrane is the outer membrane of the cell; it delimits the cell itself and a cell interior wit

Rock be well-known from living things, Critical thinking the organization o...

Critical thinking the organization of a rock is much simpler than that of living things. By what other criteria can a rock be well-known from living things? Rocks are not comp

What is excessive fat intake, What is Excessive Fat Intake? Although mi...

What is Excessive Fat Intake? Although minimum amount of fat is essential as calculated above but upper limit of fat should be drawn due to its link with an increased risk of d

Names and uses of the various laboratory tools, What are the names and uses...

What are the names and uses of the various laboratory tools? Tools are beakers, microscopes, tweezers, hot plates, lasers, test tubes, voltmeters, Erlenmeyer flasks, thermomete

How different is the amphibian heart from the fish heart, How different is ...

How different is the amphibian heart from the fish heart? The fish heart has only two chambers, a ventricle and an atrium, and the blood that comes to it is purely venous. I

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