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

Qualities of a good counsellor, It is important to know about qualities of ...

It is important to know about qualities of a counsellor because you will be counselling a diabetic patient and his family members in clinic/home/hospital and therefore, you shoul

Appendical skeleton, it consists of the girdles and the skeleton of the lim...

it consists of the girdles and the skeleton of the limbs

Determine the intracellular concentration of trva, Determine the intracellu...

Determine the intracellular concentration of TRVA Consider Neuron B in the frog central nervous system whose plasma membrane has a previously unknown channel that is selectly c

Ecosystem balance, Ecosystem Balance We take up, another parameter of ...

Ecosystem Balance We take up, another parameter of ecosystem balance. One factor that affects the stability or persistence of some ecosystems under small or moderate environme

Respiratory organ in animals, RESPIR A T ORY ORGANS IN ANIMALS - ...

RESPIR A T ORY ORGANS IN ANIMALS - In Protozoa plasmalemma functions as respiratory surface. In Porifera, respiration occur through body wall. In Coelentrata resp

What do you mean by periodical, Q. What do you mean by Periodical? A pe...

Q. What do you mean by Periodical? A periodical is a publication appearing at regular intervals. Each issue is called a number and collectively these numbers comprise a volume.

Why do preserved foods not spoil, Why do preserved foods not spoil? Pla...

Why do preserved foods not spoil? Plant and animal cells must stay in an isotonic, or neutral, solution to survive. When salt or sugar is added, more of the cells wither and di

Population growth curve, Increase in population size is known as population...

Increase in population size is known as population growth. It depends upon number of persons added to the population and number of persons lost from the population. Addition in pop

Define the primary stain and mordant, Define the Primary Stain and Mordant?...

Define the Primary Stain and Mordant? (i) Primary Stain - Crystal violet is the primary or first stain, which stains all the cells violet/purple. (ii) Mordant - Gram's iodin

Can you define termination of the stress test, Q. Can you define terminatio...

Q. Can you define termination of the stress Test? Test should be terminated when: 1) PVCS develop in pairs or with increasing frequency or when ventricular tachycardia devel

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