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

Zoology, Classification of the Phylum Protozoa up to orders

Classification of the Phylum Protozoa up to orders

How can denaturation be classified, Q. How can denaturation be classified c...

Q. How can denaturation be classified concerning its reversibility? Protein denaturation can be an irreversible or a reversible process, i.e., it may be impossible or possible

Describe protein glycosylation, Protein Glycosylation is the reaction in th...

Protein Glycosylation is the reaction in that a carbohydrate, example for a glycosyl donor that is attached to a hydroxyl or other functional set of another molecule a glycosyl acc

What is plastids, What is Plastids? The most obvious difference between...

What is Plastids? The most obvious difference between plant cells and other eukaryotic cells is that cells of most plants contain unique organelles called plastids, which inclu

Explain colloidal state, Explain colloidal state Foods contain a high ...

Explain colloidal state Foods contain a high percentage of water in which other nutrients present are dispersed. The existence of the colloidal state was first recognized by T

What are the similarities in cloning and selective breeding, Similarities ...

Similarities  in cloning and selective breeding cloning (not transgenesis) and selective breeding both transfer whole genome both selective breeding and cloning have t

Problem of potency of blastema cells, Problem of Potency of Blastema Cells ...

Problem of Potency of Blastema Cells The local cells are accountable for regeneration. Now you could ask which of the blastema cells differentiated into which type of limb ti

What is the enzyme included, Is there any situation in which DNA is made ba...

Is there any situation in which DNA is made based on a RNA template? What is the enzyme included? The process in which DNA is synthesized having as template a RNA chain is know

Define the reduction of the activation energy, How does the formation of th...

How does the formation of the enzyme-substrate complex define the reduction of the activation energy of chemical reactions? The enzyme possibly works as a test tube within whic

Define the basic function of keratin in the epidermis, Q. What is the funct...

Q. What is the function of keratin in the epidermis? The epidermis is the outer layer of the skin made of epithelial tissue in the epidermis there are keratin-secreting cells (

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