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

Difference between the concepts of karyotype and genome, What is the differ...

What is the difference between the concepts of karyotype and genome? Genome is the set of DNA molecules that characterizes each living being or every species. The concept then

Illustrate photochemical phase, Q. Which are the subproducts of the photoch...

Q. Which are the subproducts of the photochemical phase that are essential for the chemical stage of photosynthesis? The chemical stage of photosynthesis depends on ATP and NAD

Show the general taxonomic indexes, Q. Show the General Taxonomic Indexes? ...

Q. Show the General Taxonomic Indexes? The indexes serve as an aid to locate quickly the source of origin31 publications of a name, to learn if a particular name has been appli

Determine the stability of natural colorants in foods, Stability of Natural...

Stability of Natural Colorants in Foods Many attempts have been made to retain colouration by adding chemicals or modifying processing conditions. Ascorbic acid has been claime

Blood in human , why is blood called a fluid connective tissue ?

why is blood called a fluid connective tissue ?

Explain nutrient requirements during hypertension, Q. Explain nutrient requ...

Q. Explain nutrient requirements during hypertension? In order to meet the above objectives, we need to understand the nutrient requirements during hypertension. Let us start w

Energy storage, Energy Storage As we said above, food intake and ener...

Energy Storage As we said above, food intake and energy expenditure for animals is approximately equal. If energy expenditure exceeds food intake, then the excess energy is t

What is population growth rate, Q. What is population growth rate? The ...

Q. What is population growth rate? The Population growth rate (PGR) is the percent variation between the numbers of individuals in a population at two different times. Thus the

Explain phylum rhodophyta, Phylum Rhodophyta (Red algae) 1) The photosy...

Phylum Rhodophyta (Red algae) 1) The photosynthetic pigments include red pigments (phycoerythrin) and blue pigment (phycocyanin) apart from chlorophyll, of which red pigment pr

How dynamic biological processes represented as network, How dynamic biolog...

How dynamic biological processes represented as network? Many dynamic biological processes throughout a wide range of ecological scales are easily represented as dynamical netw

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