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
Respiratory System in Living Organisms Respiration is a necessary physiological process in all living organisms by which they obtain energy for carrying out all the metabolic

Define Functions of selenium in humans? Until recently, the only known metabolic role of selenium in humans was as a component of glutathione peroxidase which along with vitami

is a wheat plant a eustele or a siphonostele or a protostele?

Iodine Iodine functions are essential components of the thyroid hormones thyroxine (T 4) and triiodothyronine (T3), which regulate the rate of energy metabolism. Absorbed iodi

Nursing  Education   Computer-Assisted Instruction (CAI) is a valuable teaching aid for health care students, testing them with frequent quizzes to ensure that the material rea

What is the difference between the amphibian heart and the reptile heart? The reptiles have double and incomplete circulation too, three heart chambers (two atria and one ventr

2. Vaccinations against various childhood diseases have contributed to the entry of women, particularly mothers, into the fulltime workplace. a. Is this statement supported by data

Q. What is the difference between diffusion and osmosis? Osmosis is the phenomenon of movement of solvent particles in general, water from a region of lower solute concentratio

what is mode of nurtion of earth worm/

In an experiment, isolated chloroplast thylakoids were incubated at pH 4.0 with ADP and inorganic phosphate (Pi) added to the medium and then transferred to a medium having pH 8.0.