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 biosynthetic pathways, The intermediates in the cycle give precurso...

The intermediates in the cycle give precursors for various biosynthetic pathways. An instance is as given below: -  From citrate synthesis of fatty acids; -  Amino acid synth

Standard titration - estimation of vitamin c in chillies, Define Standard t...

Define Standard titration - estimation of vitamin c in Chillies? Pipette 5 ml of standard ascorbic acid solution into a 100 ml conical flask. Fill the burette with the dye solu

Digestion of nucleic acids, Digestion of Nucleic Acids Several nuclease...

Digestion of Nucleic Acids Several nucleases present  in  the  pancreatic juice  like RNAase and  DNAase  digest various nucleic acids- These enzymes  are endonucleases which h

Goal of bcc programme, The overall goal of BCC programs for diabetes mellit...

The overall goal of BCC programs for diabetes mellitus is to promote behaviors that control diabetes mellitus and prevent complications. These include: Following treatment

Which are plant tissues that form the plant roots, Which are plant tissues ...

Which are plant tissues that form the plant roots? Roots have a central portion called medulla made of vascular tissue outer phloem and inner xylem. Medulla is delimited by per

Explain about the pasteurization, Explain about the Pasteurization? You...

Explain about the Pasteurization? You must be aware of the various pasteurized products available in the market. The most commonly used product being ‘milk'. Why do we need to

Determine the initiation of muscle contraction, Describe the Capillarity Th...

Describe the Capillarity Theory in respect of ascent of water in plants. Name the tissue included. Determine the initiation of muscle contraction. What is the role of Sarcoplas

Eukaryotic chromosomes, The vast amount  of genomic  DNA in a eukaryotic  c...

The vast amount  of genomic  DNA in a eukaryotic  cell is strongly  packaged  in chromosomes  having  within  a specialized  organelle and  the nucleus.  This very vast amount of e

Homologous series, Homologous series A homologous series can be illust...

Homologous series A homologous series can be illustrated as a group of compounds in which the several members have similar structural features and identical chemical propertie

Neurochemistry of consciousness, Conscious experience is probably the most ...

Conscious experience is probably the most familiar mental process that we know, yet its workings remain mysterious. Consciousness is not directly accessible for study. Hence the ne

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