Release of microspores, Biology

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.

Posted Date: 1/23/2013 1:02:19 AM | Location : United States







Related Discussions:- Release of microspores, Assignment Help, Ask Question on Release of microspores, Get Answer, Expert's Help, Release of microspores Discussions

Write discussion on Release of microspores
Your posts are moderated
Related Questions
Contagious bovine pleuropneumonia (CBPP) This is a highly fatal disease of cattle and of major economic importance in certain tropical countries. It also affects buffaloes, bis

Explain saturated fatty acids Some of the more significant saturated fatty acids with their systematic and common names are listed in table, and some of the unsaturated fatty a

A dihybrid cross yields 320 F2 offspring. How many are expected to resemble the homozygous recessive parental?

Transmissible spongif orm encephalopathies Transmissible spongiform encephalopathies (TSEs, also called Prion diseases) are fatal neurodegenerative diseases such as scrapie of

What is the action mechanism of the antibiotic penicillin? Penicillin, discovered by the Scottish doctor Alexander Fleming in 1928, is a drug that inhibits enzymes essential fo

Leishmanias – Flagellates Species of the genus Leishmania are parasites of mammals including man. Leishmanias infections occur over wide regions of the world from Asia, the ne

Fatty acid synthesis is the formation of fatty acids from malonyl-CoA and acetyl-CoA precursors by action of enzymes called as fatty acid synthases. It is a very significant part o

The Deoxyribonucleic acid or also called as DNA molecules are informational molecules encoding the genetic instructions used in the functioning and development of all known living

How does the sodium-potassium pump present in the cell membrane work? What is the importance of this protein for the cell? The sodium-potassium pump is the transport protein th