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

Elaborates congenital aortic stenosis in details, Elaborates Congenital Aor...

Elaborates Congenital Aortic Stenosis in details? More common in males (4: 1). High incidence of Bicuspid Aortic valve. Murmur present from early infancy and sometimes at birth

Define photoorganoheterotrophs and chemoorganoheterotrophs, Photoorganohete...

Photoorganoheterotrophs and Chemoorganoheterotrophs - Nutritional Types (1) Photoorganoheterotrophs - These microorganisms use light as a source of energy and organic compound

PHYLUM MOLLUSCA, how we attempt a question of phylum mollusca in exame?

how we attempt a question of phylum mollusca in exame?

Diestrus- estrous cycle, Diestrus- Estrous cycle This lasts 60 to 70 h...

Diestrus- Estrous cycle This lasts 60 to 70 hours during which functional regression of the corpora lutea occurs. The uteri are small, anaemic, and only slightly contractile.

Determine the molecular function, Please answer the following three questio...

Please answer the following three questions on Sequence Z: Metadata The GO Ontology is a very widely-used resource in the bioinformatics community as a tool to annotate

Iron deficiency anaemia, Iron Deficiency Anaemia   This is the most com...

Iron Deficiency Anaemia   This is the most common nutritional and haematologic disorder  in infancy and chhildhood in developing countries. It is caused by lack of sufficient i

Phylem protozoa, how does these phylem parasites????

how does these phylem parasites????

Explain gametophyte, "In these autotrophs, sporophyte is the dominant gener...

"In these autotrophs, sporophyte is the dominant generation. Gametophyte is also photosynthetic and not dependent on sporophyte for nutrition."  These autotrophs are:  a.  P

Why similarities in body parts often indicate shared, Similarities in body ...

Similarities in body parts often indicate shared ancestry. Which of the following is true? Structures used for different purposes in different groups can be controlled by the same

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