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

What is pulmonary stenosis, Pulmonary Stenosis :  The obstruction may be v...

Pulmonary Stenosis :  The obstruction may be valvar, infundibular or supra valvar.

Indications for surgery-aortic valve disease, Indications For Surgery :...

Indications For Surgery :  The normal aortic valve area in the adult is about 3-4 cm2. Significant symptoms occur when the valve area is seduced to 1/4"' the normal area

Digestive system, Explain the process by which the kidney varies the volume...

Explain the process by which the kidney varies the volume and concentration of urine

Gene clonning, Inportant step for gene clonning

Inportant step for gene clonning

Explain about the dehydration, Explain about the Dehydration? Dehydrati...

Explain about the Dehydration? Dehydration is defined as the excessive loss of body water. It may occur because of inadequate intake, or abnormal loss of body water or a combin

In which way bacteria and the archaea different, How are the bacteria and t...

How are the bacteria and the archaea different from all the other cellular microbes? -They have cell walls? -They can move? -They reproduce asexually? -They have no nucleus?

Define transcellular fluid compartment - extracellular fluid, Define transc...

Define transcellular fluid compartment - extracellular fluid? The transcellular fluid is a small compartment that represents all those body fluids which are formed from the tra

Malnutrition related diabetes mellitus, Q. Explain about Malnutrition Relat...

Q. Explain about Malnutrition Related Diabetes Mellitus? This type of diabetes has been categorized as a separate entity. 'if is 'Men seen commonly in developing countries, 1n

Explain vanishing points., A vanishing point is where parallel lines that m...

A vanishing point is where parallel lines that move off into the distance seem to converge. It's an artifact of perspective. The vanishing point for any set of lines that are paral

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