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 the plant hormone remarkable for stimulating, What is the plant hor...

What is the plant hormone remarkable for stimulating flowering and fruit ripening? What are the uses and practical inconveniences of that hormone? The plant hormone notable for

What are the female pronucleus, What are the female pronucleus and the male...

What are the female pronucleus and the male pronucleus? The female pronucleus is the proper haploid nucleus of the egg cell. Male pronucleus is the haploid nucleus of the sperm

Explain the maltose and cellobiose, Explain the Maltose and Cellobiose? ...

Explain the Maltose and Cellobiose? Maltose consists of two a-D-glucose molecules with the alpha bond at carbon 1 of one molecule attached to the oxygen at carbon 4 of the se

Mode of nutrition, What is the mode of nutrition of Ascaris?

What is the mode of nutrition of Ascaris?

Subtropical rain forests - ecosystem, Subtropical rain forests - Ecosystem ...

Subtropical rain forests - Ecosystem In regions of fairly high rainfall but less temperature differences between winter and summer and broad-leaved evergreen subtropical biome

How tyndallisation used for sterilization, Q. How Tyndallisation used for s...

Q. How Tyndallisation used for sterilization? John Tyndall devised a process of sterilisation by steaming for a few minutes at 100 o C on 3-4 successive operations separated by

Name the joint disorders that s more a risk, In Reggie's case, he fractured...

In Reggie's case, he fractured the proximal end of his right femur, an integral component of his hip. Name the joint disorders that Reggie is more a risk of in (a) the short term a

How does caffeine effect plant growth, How does caffeine effect plant growt...

How does caffeine effect plant growth? Minerals like potassium are often found alongside caffeine when it happens in plant sources like coffee beans, and that could help the pl

Human reproduction, what stimulate pituitary to release the hormone respons...

what stimulate pituitary to release the hormone responsible for paturation name the hormone

Earthquake energy, Large Quantity of energy is released during an earthquak...

Large Quantity of energy is released during an earthquake with a combination of radiated elastic strain seismic waves frictional, heating of the fault surface and cracking of the r

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