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

System that permits movement and fixation to echinoderms, What is the syste...

What is the system that permits movement and fixation to echinoderms? The system that allows movement and fixation to substrates in echinoderms is known as the ambulacral syste

Domestic waste water management, All the water used in the home that goes i...

All the water used in the home that goes into the drain or into sewage collection system is called waste water. Domestic sewage is the waste water from kitchens, bathrooms etc. It

Haemorrhagic septicaemia, H a e m o r r ha g i c septicaemia ...

H a e m o r r ha g i c septicaemia It is also known as septicemic pasteurellosis or barbone and the disease is clinically characterized by high fever, excessive saliv

Define drug effects on carbohydrate metabolism, Define drug effects on Carb...

Define drug effects on Carbohydrate metabolism? Carbohydrate metabolism: Hypoglycemic drugs such as insulin and sulphonylureas are prescribed because of their ability to increa

What anatomical direction with respect to occipital cortex, The frontal cor...

The frontal cortex is in what anatomical direction with respect to the occipital cortex? a. anterior b. posterior c. sagittal d. inferior

Illustrate the functioning of comprehensive model, Illustrate the functioni...

Illustrate the functioning of comprehensive model 1) Provide continuity in understanding developmental progress, or lack thereof, in those disorders that affect neurological de

Define biocompatible and biodegradable material, 1. Define each term and gi...

1. Define each term and give an example of an application that uses the following: a. Biocompatible material b. Biodegradable material c. Biomimetic

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