Egg - synergids, Biology

Assignment Help:

Egg - Synergids

The three cells of the egg apparatus are arranged in triangular fashion with the egg sharing a common wall with the two synergids and the central cell. In the egg the wall is thicker at the micropylar end and is absent at the chalazal end. At this end the lateral walls of the egg cell appear to join the central cell wall. The egg cell wall is traversed by plasmodesmata on the sides of the two synergids and the central cell but not at its outer face. The egg cell becomes highly polarized early in its development. Polarity is expressed by the aggregation of cytoplasmic elements at the chalazal end of the cell. The micropylar end of the cell is occupied by a large vacuole. Thus, the distribution of the vacuole and cytoplasm in the egg cell is just the opposite of that in the synergids.

The ultra structure of the egg cytoplasm indicates that it is inactive. The mitochondria show only a few cristae. But for Zea mays, dictyosomes are either absent (Epidendrum) or are only a few in numbers. Where present, the dictyosomes exhibit an inactive state. Plastids are present in the egg; they often contain a striking difference from the male gametes. The egg cytoplasm is rich in ribosomes. In Plumbago capensis where the embryo sac lacks synergids. However many finger- like wall projections arise at the micropylar end of the egg cell. They resemble the filiform apparatus of the synergids. In this plant the egg cell seems to have taken over the role of synergids in addition to its own gametic function.


Related Discussions:- Egg - synergids

Sporogenous tissue, Sporogenous Tissue The primary sporogenous cells (...

Sporogenous Tissue The primary sporogenous cells (PSCs) result after the periclinal division of the archesporial cells. The PSCs may undergo mitotic divisions and increase in

Can you explain bauhin binomial system, Q. Can you explain Bauhin? We g...

Q. Can you explain Bauhin? We got the first reference of binary use of species name in Pinax (1623), a publication of a Swiss physician and botanist Casper Bauhin (1560-1624).

What is the function of lymph nodes, Explain function of lymph nodes? L...

Explain function of lymph nodes? Lymph nodes have white blood cells which ingest bacteria and prevent them from reaching the circulation.

Ecology, In what manner is the ecosystem concept useful in the study of env...

In what manner is the ecosystem concept useful in the study of environment

Explain conventional factors for cad, Explain Conventional Factors ? Sm...

Explain Conventional Factors ? Smoking, Hypertension, diabetes mellitus, obesity, hypercholesterolemia, and reduced physical activity are considered as conventional risk factor

What is double labelled water (dlw), What is Double Labelled Water (DLW)? ...

What is Double Labelled Water (DLW)? Technique DLW is currently considered the most accurate technique for measuring TEE in free- living individuals. It is the method used to m

Why carbon monoxide considered inorganic compounds, Why are calcium carbona...

Why are calcium carbonate and carbon dioxide and carbon monoxide considered inorganic compounds? "The name "organic" is a historical name, dating back to 19th century, when it

Describe about the argyll robertson pupil, Describe about the Argyll Robert...

Describe about the Argyll Robertson Pupil (ARP) Argyll Robertson Pupil (ARP) occurs in patients who have tertiary syphilis. There is a "light-near dissociation" because pupils

Types of community, Types of Community On the basis of size and degree ...

Types of Community On the basis of size and degree of relative independence communities may be divided into two types: i) Major Community: These are large-sized, well org

Discuss about nerve to mylohyoid, Nerve to Mylohyoid Motor branch of i...

Nerve to Mylohyoid Motor branch of inferior dental nerve which descends in a groove on the medial surface of the mandibular ramus. Surgical intervention in this area may lead

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