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

#title.how can help me solve this problem?, i have a question on how to pro...

i have a question on how to proceed the fomular of delete the gene on the human body.

Which animals maintain constant body temperature?, Which of the below terms...

Which of the below terms is used to describe animals which maintain a constant body temperature by producing heat by metabolic oxidations (muscle contractions) and losing excess he

Phanerophytes - classes of life form, Phanerophytes - Classes of Life Form ...

Phanerophytes - Classes of Life Form The perennating buds in this case are present on erect, negatively geotropic shoots, much above the ground. These buds are naked or least

Thermodynamics and cell shapes, Thermodynamics and Cell Shapes Why are...

Thermodynamics and Cell Shapes Why are protoplasts (cells devoid of cell wall) spherical? Why are most of the unicellular organisms (prokaryotes and eukaryotes) spherical? A s

Explain procedure for preparation of general purpose media, Explain the Pro...

Explain the Procedure for Preparation of General Purpose Media Procedure: Now prepare the media following the steps enumerated herewith: 1. Weigh and dissolve each ingredien

What do you understand by melanocytes, Q. What are melanocytes? Melanoc...

Q. What are melanocytes? Melanocytes are epithelial cells of the skin specialized in secretion of melanin and Melanin is a pigment that besides coloring the iris of the eye and

Function of dopamine in consciousness, Q. Function of Dopamine in conscious...

Q. Function of Dopamine in consciousness? An increase in dopamine activity produces an increase in wakefulness. Dopaminergic neurons in the ventral tegmental areas are constant

What are biopolymers, Q. What are biopolymers? Polymers are macromolecu...

Q. What are biopolymers? Polymers are macromolecules made by the union of several smaller identical molecules, called monomers. Biopolymers are polymers present in the living b

Omni science valve-types of valves, Omni Science Valve :  Thi...

Omni Science Valve :  This is another type of tilting disc valve available from 1978. The cage is made of titanium and disc out of pyrolitic carbon. There have been a

Tissue culture, Note on production of haploid by tissue culture.

Note on production of haploid by tissue culture.

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