Gonial apospory and somatic apospory, Biology

Assignment Help:

Gonial Apospory and Somatic Apospory

Gonial Apospory

There is no meiosis. The megaspore mother cell enlarges; a small vacuole appears above and below the nucleus. The cell thus becomes 1-nucleate embryo sac. Three successive mitotic divisions result into an 8-nucleate embryo sac. In Brachycome, the polar nuclei function directly as the first 2 endosperm nuclei.

Somatic Apospory

Meiosis is apparently normal but megaspores play no part in the embryo sac formation. Either during or soon after meiosis one or more sporophytic cells (nucellar or chalazal) enlarge and invade the nucellar lobe destroying and replacing the megaspore. After 3 successive nuclear divisions each such cell becomes differentiated into an aposporic 2n embryo sac with normal organization. Thus, gametophytic generation is completely eliminated.


Related Discussions:- Gonial apospory and somatic apospory

Medtronic-hall valve-types of valves, Medtronic-Hall Valve :  This is...

Medtronic-Hall Valve :  This is a low profile central tilting disc valve. The disc is made of pyrolitic carbon and housing is single piece of machined titanium. Introduced in

Parasitology, how trematodes/nematodes adapt to their parasitic mode of fee...

how trematodes/nematodes adapt to their parasitic mode of feeding

Cardiovascular, Describe the process of excitation-contraction coupling (EC...

Describe the process of excitation-contraction coupling (ECC) in the heart. How do adrenaline, noradrenaline and acetylcholine alter heart rate and or force?

Thermal stratification - lake ecosystem, Thermal Stratification - Lake Ecos...

Thermal Stratification - Lake Ecosystem Shallow lakes show no thermal stratification as their waters are well mixed, resulting in uniform temperature throughout. However lakes

Some common air pollutants: oxides of nitrogen, Oxides of nitrogen:   ...

Oxides of nitrogen:          These include nitrogen monoxide (NO) and nitrogen dioxide (NO2). NO is a colourless, odourless and inert gas but like CO it can also combine with

Osmoregulation in freshwater metazoans, Osmoregulation in Freshwater Metazo...

Osmoregulation in Freshwater Metazoans Freshwater and brackish water animals that are live in hypoosmotic(of lower osmotic pressure) environment and keep a hyperosmotic (of h

Natural selection, Which of the following statements is most acceptable fro...

Which of the following statements is most acceptable from an evolutionary point of view? (a) Apes and humans have evolved from a common ancestor. (b) Humans have evol

What is ribose, What is ribose Browning in canned fish is commonly asso...

What is ribose Browning in canned fish is commonly associated with ribose. Undesirable colour changes in shellfish during canning often involve metal  ions, for example, the bl

Explain the diagnostic set-up surgical stent, Explain the diagnostic set-up...

Explain the diagnostic set-up surgical stent The patient should understand the procedure and be warned of any complications. They should have agreed with the treatment plan, t

Criteria for identifying biodiversity hot spots, A simple method used to id...

A simple method used to identify areas of high conservation priority is the selection of countries according to highest species richness. Among the top 12 countries identified this

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