Release of microspores, Biology

Assignment Help:

Release of Microspores

Up to the tetrad stage, there is no cellulosic wall around the microspores. As you will come to know in the next unit, a unique feature of the pollen is the ornamentation of the pollen wall. This ornamentation is seen on the outer layer of the pollen or exine. The exine is made up of sporopollenin, one of the most resistant (to physical and biological decomposition) substances known in the biological world. Pollen grains of prehistoric plants are well preserved as fossils because of their exine. There is enormous variation in the ornamentation of the exine, and it is a characteristic feature of a given species. Often pollen grains of particular group of plants can be identified on the basis of their exine pattern.

The blue print of exine, termed primexine is laid down below the callose wall after the basic structural features of the exine including the position of the germ pore (a region in the pollen wall through which the pollen tube emerges) are demarcated in the primexine. This important morphogenetic event takes place while the microspores are still enclosed in the callose wall, in groups of four or at the tetrad stage. Thus, the pattern of mature exine is laid down before the spores are set free. The callose wall seems to play an important role in the orderly deposition of primexine. You will read more about this in the next unit. After the development of exine, the callose wall dissolves. The enzyme callase which dissolves the callose wall is produced by the surrounding tapetal cell pen plasmodium. The development of the male gametophyte begins after the liberation of individual microspores.


Related Discussions:- Release of microspores

Kingdom animalia, Locomotion and reproduction in echinodermata

Locomotion and reproduction in echinodermata

Describe the term physiotherapy, Describe the term Physiotherapy? Patie...

Describe the term Physiotherapy? Patients who are sedated, intubated and ventilated are not able to deep breathe, cough and clear secretions. Hence, it is important to do chest

Freshwater biomes, Low levels of dissolved salts characterise the freshwate...

Low levels of dissolved salts characterise the freshwater biomes. The salt content of fresh water is about 0.005 percent. The freshwater biomes consist of inland bodies of standing

Female gametophyte formed in angiosperms, Q. How is female gametophyte form...

Q. How is female gametophyte formed in angiosperms? Into the flower ovary there are megasporangia enclosed by a tegument having a small opening, the micropyle. Inside the megas

Alpha helix and the beta-sheet protein, What is the difference between the ...

What is the difference between the alpha helix and the beta-sheet protein conformations? Ans) Alpha helix and beta-sheet conformations are the two major types of secondary struc

How does self infection by tapeworms occur, Q. How does self infection by t...

Q. How does self infection by tapeworms occur? The Taeniasis patients may develop the most severe form of the worm infection, cysticercosis, because their feces contain eggs

Theoretical calculation of calorific value of a fuel, The calorific value o...

The calorific value of a fuel can be theoretically determined by using dulong's formula. It is assumed that heat evolved comes from the combustion of carbon, hydrogen, and sulphur

Function of the cornified layer of the skin, What are the main functions of...

What are the main functions of (a) the basal (Malpighian) layer, (b) the cornified layer of the skin?   (a) The basal (Malpighian) layer makes new skin cells and the pigment

Define milk as a rich source of protein, Define Milk as a rich source of pr...

Define Milk as a rich source of protein? A value of 3.5% protein is often considered as an average for milk. Milk protein has traditionally been divided into 2 classes - casein

ANIMAL RESPIRATION, WHAT IS THERE BETWEEN THE TRACHEA OF COCKROACH AND RABB...

WHAT IS THERE BETWEEN THE TRACHEA OF COCKROACH AND RABBIT

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