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 is class crinoidea, What is Class Crinoidea? This Class includes t...

What is Class Crinoidea? This Class includes the sea lilies and the feather stars. What makes them different from the other Echinoderms is the placement of their mouth and anus

Explain the determination of vitamin A, Determination of Vitamin A Vita...

Determination of Vitamin A Vitamin A assay is carried out by chemical method. This method is called Carr Price Reaction.   Vitamin A and the carotenoids produce an intense b

Coniferous forests and taiga, As you travel south from the tundra you will ...

As you travel south from the tundra you will enter the circumpolar belt of coniferous forests which stretches across North America to Eurasia, this region is called taiga, a world

Original cell progresses to the g2, A cell in G1 of interphase has 12 chrom...

A cell in G1 of interphase has 12 chromosomes. How many chromosomes and DNA molecules will be found per cell when this original cell progresses to the G2?

Anaphase of karyokinesis, There is no splitting of the centromere. The ...

There is no splitting of the centromere. The kinetochore fibers contract and the spindle or pole fibers elongate , As a result homologous chromosomes of each pair rather than

Extraradicular infections, Extraradicular Infections Whatever the cause...

Extraradicular Infections Whatever the cause of post endodontic disease we should do proper diagnosis to determine what is the cause; is it intra or extraradicular infection ,

26 The Human Impact on the Environment, What are the principal sources of e...

What are the principal sources of excessive nitrate and phosphate in rivers and lakes?

Define osseointegration from diffrent points of view, Q. Define Osseointegr...

Q. Define Osseointegration from patients, microscopic and biomechanical points of view. a) From the view of the patient . An implant fixture is osseointegrated if it provid

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