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

Explain the behavioural change communication, Explain the Behavioural chang...

Explain the Behavioural change communication? One of the reasons for the widespread prevalence of PEM in our country is ignorance due to illiteracy, particularly among the fema

What do you mean by oesophagitis, Q. What do you mean by Oesophagitis? ...

Q. What do you mean by Oesophagitis? We already know that oesophagus is a muscular tube 25 cm in length and basically helps in transporting the food from the mouth to stomach,

Describe methanogen archaebacteria and thermoacidophile, Q What are halophi...

Q What are halophile, methanogen archaebacteria and thermoacidophile? There are three peculiar types of archaebacteria the halophile archaebacteria only survive in salt-rich en

Types of leaves, Types of leaves Collect leaves from such plants as lil...

Types of leaves Collect leaves from such plants as lilies, bamboo, corn, willow and geraniums. View that the monocots (lily, bamboo, corn, sugar cane) have the veins running pa

Clinical evaluation of infants and young children, Clinical Evaluation of I...

Clinical Evaluation of Infants and Young Children Approaches to clinical practice advanced in recent year are mostly directed at older children and adolescents. There has not b

What substance is prepared from species of red algae, Name that gelatin-lik...

Name that gelatin-like substance which is prepared from different species of red algae growing in Asiatic waters. Prepared product appears in the form of cakes, coarse granules and

Define the petrifilm (dry film) method, Define the Petrifilm (dry film) Met...

Define the Petrifilm (dry film) Method? An alternative method to the conventional SPC is a Petrifilm (dry film) method. It is a non-petri dish plating system where a layer of n

Myocardial energetics, The oxidation of substrates like free fatty acids (F...

The oxidation of substrates like free fatty acids (FFA), glucose, lactate and ketone bodies results in the energy of Adenosine triphosphate (ATP) and Creatine phosphate (CP). The s

List the four basic points of food exchange, List the four basic points to ...

List the four basic points to be kept in mind when advising food exchange. To develop the food exchange list points to keep in mind are: a) Group similar foods in one group.

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