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

What two characteristics unique and different from others, In general compa...

In general compare and contrast the three functional classifications of joints according to movement. What are two characteristics that make synovial joints unique and different fr

Name the three main arthropod classes, How are the three main arthropod cla...

How are the three main arthropod classes characterized according to the body division? In crustaceans and arachnids the head is fused with the thorax forming the cephalothorax.

Cellular specific immune response, Q. What is the difference between cellul...

Q. What is the difference between cellular specific immune response and humoral specific immune response? Humoral specific immune response is the defense system by means of, an

Tropical rain forests - ecosystem, Tropical rain forests - Ecosystem T...

Tropical rain forests - Ecosystem Tropical rain forests occur near the equator. Tropical rain forests are among the most diverse communities on the earth. Both temperature and

Limitations of doppler echocardiograph, Though  it has bees suggested that ...

Though  it has bees suggested that Doppler echocardiography may be useful for non-invasive determinations of  stroke volume and cardiac output, it  should be recognized that th4re

Strategies for help of diabetic patients, It is important that when patient...

It is important that when patients change behaviour they expectt to see results quickly; therefore, the new behaviour must have advantages. So someone who wants to control blood su

What is the name of the dna duplication process, What is the name of the DN...

What is the name of the DNA duplication process? What is the main enzyme that participates in it? The process of copying, or duplication, of the DNA molecule is called replica

How many carbon dioxide molecules are liberated, How many carbon dioxide mo...

How many carbon dioxide molecules are liberated after each cycle of the Krebs cycle? For a single glucose how many carbon dioxide molecules were already liberated by the aerobic re

Compute the diffusion coefficient of a protein, Calculate the diffusion coe...

Calculate the diffusion coefficient of a protein bovine serum albumin at 23 degree Celsius?

Explain the limiting factors for the growth of a population, What are the m...

What are the main limiting factors for the growth of a population? The factors that limit the growth of a population can be divided into biotic factors and abiotic factors. The

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