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

How many larvae per treatment, A study is made to verify the effects of pes...

A study is made to verify the effects of pesticide exposure on pupal weight of butterflies. In a pilot study, 5 randomly selected larvae are raised on plants exposed to the pestici

Porcine rotavirus, Porcine rotavirus Piglet diarrhoea and mortality are ga...

Porcine rotavirus Piglet diarrhoea and mortality are gaining importance and the viral agent which is highly incriminated in such episodes is porcine rotavirus. The clinical featur

What are the main human diseases caused by prions, Q. What are the main hum...

Q. What are the main human diseases caused by prions? The major known human diseases of such type are the Creutzfeldt-Jacob disease (CJD), the kuru and the Gerstmann-Sträussle-

Phylum, detail study of coelenterata

detail study of coelenterata

Explain the management of canal impediment, Management of Canal Impediment ...

Management of Canal Impediment a) Impediments are iatrogenic mishaps resulting from vigorous instrument short of the b) Appropriate working length and failure to confirm api

Poultry and duck diseases-avian leucosis complex (alc), Avian leucosis comp...

Avian leucosis complex (ALC) The disease in poultry is caused by an RNA virus classified under avian type C Retrovirus group under the family Retroviridae. Epidemiology:

Why do roots of many swamp plants have a special morphology, Why do roots o...

Why do roots of many swamp plants have a special morphology? Swamp and marsh plants usually present supporting roots that ramify from portions of the stem above the ground help

What are the major natural plant hormones and their effect, What are the ma...

What are the major natural plant hormones and what are their respective effects? The major natural plant hormones and their respective functions are the following- Auxins that

Invertebrates - osmotic and ionic regulation, Invertebrates - Osmotic and I...

Invertebrates - Osmotic and Ionic Regulation Regulation of water and ions in invertebrates is done by neuroendocrine mechanism. It operates at the level of Malpighian tubules

Is the esophagus a muscular organ, Is the esophagus a muscular organ? Why e...

Is the esophagus a muscular organ? Why even in a patient lying totally flat on a hospital bed can the swallowed food reach the stomach? The esophagus is a predominantly muscula

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