Polygonum type - monosporic embryo sacs, Biology

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.

Posted Date: 1/23/2013 1:46:50 AM | Location : United States







Related Discussions:- Polygonum type - monosporic embryo sacs, Assignment Help, Ask Question on Polygonum type - monosporic embryo sacs, Get Answer, Expert's Help, Polygonum type - monosporic embryo sacs Discussions

Write discussion on Polygonum type - monosporic embryo sacs
Your posts are moderated
Related Questions
Explain about the Nucleoproteins? Nucleoproteins are combinations of nucleic acids land simple proteins, which usually consists of a large number of basic amino acids. Nucleopr

Q. Explain Restrictive cardiomyopathy? It is a systemic or idiopathic disorder of the myocardium with clinical and hemodynamic features of diastolic dysfunction, closely simula

Indications i) When there is an abnormal rise in the bilirubin level which may be due to physiological or pathological jaundice or any other problem. ii) Prophylactic ph

The stress lab must have the following equipment: 1) A mercury Blood Pressure apparatus. 2) A Bed so that the patients ECG can be recorded in the recovery period in supine po

Q. Concerning solubility, how are the lipids classified? Oils and Fats are hydrophobic molecules, i.e., they are insoluble in water and non polar. Lipids in general are molecul

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

Define Classification of functions of minerals?  The varied functions of minerals can be grouped under four general physiologic roles viz. Structural: They form an integ

What is a trace element and how are they important in organisms, give an example.

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

PEROXISOMES AND GLYOXYSOMES Certain small ovoid  unit membrane bound  sac like  cytoplasmic  organelles, resembling  lysosomes in size  and appearance  were  isolated  from var