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 are the phytoplankton and the zooplankton?, What are the phytoplankton...

What are the phytoplankton and the zooplankton? The Phytoplankton and the zooplankton are divisions of the plankton. The phytoplankton includes the autotrophic floating beings:

Explain about the ph - nutritional biochemistry, Explain about the PH - Nut...

Explain about the PH - Nutritional Biochemistry? You have already studied about pH in your undergraduate years and know what it means. Yes, mathematically we can define pH as e

What is dip stick test, What is Dip Stick Test It is a rapid method of ...

What is Dip Stick Test It is a rapid method of detection of Ketone bodies which you can perform easily. Plastic strips impregnated with a buffered mixture of sodium nitropru

What is osseointegration, What is Osseointegration Osseointegration was...

What is Osseointegration Osseointegration was the hallmark of success in implant dentistry in the 1980s. It was believed that an implant was successfully integrated when there

Sedge-meadow stage - hydrarch, Sedge-Meadow Stage - Hydrarch Favoured ...

Sedge-Meadow Stage - Hydrarch Favoured by an increasing amount of light, as the former occupants disappear, they gradually change the reed swamp into a sedge meadow. And now s

Point and non-point sources, Point and Non-Point Sources The discharg...

Point and Non-Point Sources The discharge of effluents in receiving water body at a specific site are referred to a point sources in contrast to the inflow of pollutants in a

How does menstrual cycle begin, Does the hypophysis-ovaries endocrine axis ...

Does the hypophysis-ovaries endocrine axis work in the same way during pregnancy as in non-pregnant women? If pregnancy does not occur how does another menstrual cycle begin? T

What is the dichogamy, What is the dichogamy? Dichogamy is phenomenon o...

What is the dichogamy? Dichogamy is phenomenon of the maturation of female reproductive structures of the plant in a different period to the maturation of the male reproductive

Define classification of lipids, Define Classification of Lipids? Chemi...

Define Classification of Lipids? Chemically, lipids are the organic molecules poor in oxygen content, soluble in organic solvents but insoluble in water. They are classified as

Benefit of hypothermic, Normal 0 false false false EN-I...

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

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