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

Find if the sugar is a d- or l- stereoisomer, If carbon 1 is the carbonyl g...

If carbon 1 is the carbonyl group of a 6-carbon aldose (aldohexose), which carbon determines if the sugar is a D- or L- stereoisomer? Select one: a. 1 b. 2 c. 3 d. 4

Unit membrane model, structure explanation of unit membrane model

structure explanation of unit membrane model

Bud dormancy - plant growth substances, Bud Dormancy - Plant Growth Substan...

Bud Dormancy - Plant Growth Substances Environmental Factors The most important factor inducing dormancy appears to be photoperiod. Short days induce dormancy in many w

Evolution of the cell, EVOLUTION OF THE CELL All the living organisms a...

EVOLUTION OF THE CELL All the living organisms are made up of cells. A living cell may be defined as a compartment enclosed by a membrane that consists of several chemical cons

How many meters long is the molecule, E. coli DNA has a MW of about 2.7 x 1...

E. coli DNA has a MW of about 2.7 x 10^9 Daltons. How many meters long is this molecule and what does this tell you about the state of the intracellular DNA? ( The lenght of a sing

Explain the postoperative nutritional care, Explain the Postoperative Nutri...

Explain the Postoperative Nutritional Care? The therapeutic goal for the post-operative patient is rapid recovery to normal function and well being, minimum complications and e

Define intentional adulteration - types of adulteration, Define Intentional...

Define Intentional Adulteration - Types of Adulteration? In intentional adulteration, the substance is added, removed or substitute knowingly by the adulterator for the purpose

Why is the important when blood is flowing, Where are the openings into the...

Where are the openings into the coronary arteries? Why is this important when blood is flowing?

What are the lethal genes, What are the lethal genes? The Lethal genes ...

What are the lethal genes? The Lethal genes are genes having at least one allele that, while present in the genotype of an individual, causes death. There are dominant lethal a

Explain preparation and properties of modified starches, Preparation and pr...

Preparation and properties of modified starches Improved performance of starches may  be realized by physical and chemical modifications. The major physically modified starch i

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