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

Clinical symptoms of hiv, Clinical symptoms of HIV Generally, a person ...

Clinical symptoms of HIV Generally, a person infected with HIV does not show any apparent symptoms for a number (3 to 12) of years. Ten to fifteen percent infected people may,

Chlorophyll and osmosis, Hello, I did a experiment: I used 5 salt solution...

Hello, I did a experiment: I used 5 salt solutions (0 g/L; 5 g/L; 10 g/L; 15 g/L; 20 g/L), and in each one I cooked beans (25 g) for 5 minutes. At the end, I measured the absorpti

Formula concentration and supplementation - calorie density, Define Formula...

Define Formula Concentration and Supplementation - Calorie Density? Formula Concentration can be done by decreasing the amount or water added in the mixing of the formula. Sta

How the arrangement of cells helps with tissue functioning, PROVIDE a speci...

PROVIDE a specific example for epithelial and connective tissues, how the arrangement of cells helps with tissue functioning?

Body temperature and room temperature , You ran both a body temperature and...

You ran both a body temperature and room temperature test for each enzyme you tested. Did the two temperatures seem to have an effect on the enzyme Exercise? Why or why not?

What is vdrl test & rpr test, Question 1 List the cells and organs involve...

Question 1 List the cells and organs involved in immune system. Explain the role of thymus in development of T cells. Add a note on recognition of self antigens by immune system

Describe splitting of in second heart, Describe Splitting of S 2 ? On...

Describe Splitting of S 2 ? On inspiration: The split widens as both A, and Pi move away from each other with p, moving out more. The negative intrathoracic pressure during

Explain the formation of enzyme, Explain the Formation of enzyme? Form...

Explain the Formation of enzyme? Formation of enzyme: Vitamin D is essential for the formation of two enzymes -  alkaline phosphtase in the intestinal lining (involved in cal

What are the female pronucleus, What are the female pronucleus and the male...

What are the female pronucleus and the male pronucleus? The female pronucleus is the proper haploid nucleus of the egg cell. Male pronucleus is the haploid nucleus of the sperm

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