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

Define water as a medium and solvent, Define Water as a medium and solvent?...

Define Water as a medium and solvent? Water is the medium of all cell fluids, including digestive juices, lymph, blood, urine, and perspiration. All the physiochemical reaction

Explain effect of irradiation on nutrients, Normal 0 false fa...

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

How to increase in sodium conductance, How to increase in sodium conductanc...

How to increase in sodium conductance A complete motor neuron is removed from a frog and placed in normal physiological saline at 1 AM.  The neuron is healthy.  At 2 AM, the ph

Explain about tropical rain forests, Q. Explain about Tropical Rain Forests...

Q. Explain about Tropical Rain Forests? As you approach the equator the climate becomes increasingly hot and seasonal variation in climate decreases resulting in practically th

Explain in brief about unicellular “animals”, Single-cell organisms, protis...

Single-cell organisms, protists, have always been a problem for taxonomists who have trouble describing categories for organisms. Their mixed feeding habits that include being capa

What is right patellar tendon, What is right patellar tendon Which of t...

What is right patellar tendon Which of the following occur in response to an increase in the length of the right knee extensors in response to a quick tap applied to the right

Explain about the amino acids and proteins, Explain about the Amino Acids a...

Explain about the Amino Acids and Proteins? We shall now study the properties of amino acids which we know are the building blocks of proteins.  In this practical, we shall car

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

Organs involved in the digestion process, The various organs involved  in...

The various organs involved  in  the digestion process are: Alimentary tract which  includes mouth, pharynx, esophagus stomach, small intestine, large intestine, appendix,  rec

State the exocytosis in a skeletal muscle, Exocytosis in a skeletal muscle?...

Exocytosis in a skeletal muscle?   A.  During exocytosis in a skeletal muscle, there will be release of calcium ions from intracellular vesicles in the sarcoplasmic reticulum i

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