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

Taxonomic classification, flying fish,cuttlefish,silverfish - pisces are co...

flying fish,cuttlefish,silverfish - pisces are correctly matched with taxonomic classification

Illustrate about whey protein, Illustrate about Whey protein Whey prote...

Illustrate about Whey protein Whey protein concentrate (WPC) is a highly nutritious ingredient manufactured from fresh dairy whey and it is spray dried to provide an excellent

Explain karyotype - animal taxonomy, Explain Karyotype - Animal Taxonomy? ...

Explain Karyotype - Animal Taxonomy? In animals systematic, it is the karyotype, that is the chromosome number and structure which are used quite extensively either separately

What is osmotic pressure, What is osmotic pressure? Osmotic pressure is...

What is osmotic pressure? Osmotic pressure is the pressure formed in an aqueous solution by a region of lower solute concentration upon a region of higher solute concentration

Define the concept of health care, Define the Concept of Health Care? W...

Define the Concept of Health Care? We are aware of the fact that health is a fundamental human right. Thus, it becomes imperative for the State to assume responsibility for the

Calculate the volume of a 25% urethane solution, Assume that the blood volu...

Assume that the blood volume of a rabbit is 0.5 liters. If the effective dose of the anesthetic urethane is 10 micrograms/mL, calculate the volume of a 25% urethane solution that m

Impediments to infuse biology - lack of trained people, Define Impediments ...

Define Impediments to infuse biology - Lack of trained people? At present, biologists as a rule have not been trained sufficiently in quantitative approaches. A heavy dose of m

Basic working of midbrain, Q. Basic working of Midbrain? Midbrain: Also...

Q. Basic working of Midbrain? Midbrain: Also known as the mesencephalon, this part is located behind the frontal lobes and in the center of the entire brain. It deals with func

Classification, what is the mode of nutrition in fungi?

what is the mode of nutrition in fungi?

What are called transactions, What are called Transactions? The grouped...

What are called Transactions? The grouped SQL statements are known as Transactions (or) A transaction is a collection of actions embused with ACID properties.

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