Polygonum type - monosporic embryo sacs, Biology

Assignment Help:

Polygonum Type - Monosporic Embryo Sacs

The embryo sac is formed from the chalazal megaspore in the tetrad and is eight-nucleate. The development of the embryo sac begins with elongation of the functional megaspore. Initially, the megaspore cytoplasm is non-vacuolated but later small vacuoles appear which fuse to form a large vacuole. The spindle of the nuclear division in the megaspore is oriented along the long axis of the cell. Wall is not formed after the nucleus divides.

A large central vacuole appears between the two daughter nuclei. It expands and pushes the nuclei towards the opposite poles of the cell. Both the nuclei divide to form four nuclei, two at each pole. By a further division an eight nucleate condition is reached. This is followed by cellular organisation of the embryo sac. Out of the four nuclei at the micropylar end of the sac, three organize into egg apparatus and the fourth is left free in the cytoplasm of the central cell as the upper polar nucleus. Similarly, three nuclei of the chalazal quartet form three antipodal cells; the fourth one functions as the lower polar nucleus. Eventually, the latter comes to lie close to the upper polar nucleus.


Related Discussions:- Polygonum type - monosporic embryo sacs

Determine the occurrence of vitamin B12, Occurrence of vitamin B 12 Vi...

Occurrence of vitamin B 12 Vitamin B 12 is one of the cobalamin, a group of active principles widely occurring in nature. Vitamin B 12 is present especially in liver, kidney

Transcription of protein-coding genes in eukaryotes, The Protein synthesis ...

The Protein synthesis is very significant because it is by the use of genetic information to synthesize proteins in which the genes in the DNA are expressed in the phenotype. Make

What are the main sources of mercury pollution, What are the environmental ...

What are the environmental harms caused by mercury pollution? What are the main sources of mercury pollution? Mercury is a metal that when present in the water of lakes, river

Euglena, Take the prepared slide of Euglena and focus it first under low po...

Take the prepared slide of Euglena and focus it first under low power and next under the high power of tlie microscope. Observe tlie following characteristics: i) Euglena is an

Explain changes in body tissue compartments - underweight, Explain the Chan...

Explain the Changes in Body Tissue Compartments - Underweight? The severity of nutritional deprivation determines the extent of changes in the body tissue compartments. The fir

Explain starch phosphates monoesters, Explain Starch phosphates monoesters ...

Explain Starch phosphates monoesters and  Hydroxypropyl starches   Starch phosphates monoesters Emulsifying agent and thickening agent. Hydroxypropyl starches

Submerged stage - hydrarch, Submerged Stage - Hydrarch This habitat wh...

Submerged Stage - Hydrarch This habitat which is now shallower and is richer in nutrients and where light is available up to a certain depth, becomes suitable for the growth o

Where in the cell can ribosomes be found, Where in the cell can ribosomes b...

Where in the cell can ribosomes be found? What is the main biological function of ribosomes? Ans) Ribosomes can be found free in the cytoplasm, adhered to the outer side of the

High energy fixation - nitrogen fixation, High energy fixation - Nitrogen F...

High energy fixation - Nitrogen Fixation Through cosmic radiations, lightning, volcanic activity and meteorite trails which provide the high energy needed to combine atmospher

Explain didanosine and its adverse effects, Didanosine (ddl, Videx)   Di...

Didanosine (ddl, Videx)   Didanosine is available as buffered tablets, buffered or non-buffered powder, and non-buffered enteric-coated capsules (Videx EC). Adverse effects

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