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

Define etiology - anorexia nervosa, Define Etiology - Anorexia Nervosa? ...

Define Etiology - Anorexia Nervosa? The exact cause of eating disorders is not known. It is multi factorial in origin in which the personality of the patient, family relationsh

Digestive system of an arthropod, how does the digestive system of an arthr...

how does the digestive system of an arthropod operate

Define recommended dietary allowances for vitamin d, Define Recommended Die...

Define Recommended Dietary Allowances for Vitamin D? The recommendations of vitamin D are expressed as IU. 1 IU is defined as the activity contained in 0.025 mcg of cholecalci

What are biopolymers, Q. What are biopolymers? Ans. Polymers are m...

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

Define proteins, Define Proteins, Carbohydrates required for anorexia nervo...

Define Proteins, Carbohydrates required for anorexia nervosa? A. Proteins To ensure adequacy, minimum protein intake should equal the recommended dietary intake for age and

Upwelling zones of high biological productivity, Upwelling zones of high bi...

Upwelling zones of high biological productivity are found along the western coasts of the major continents. What causes this upwelling? a- cold currents moving from the equator tow

Explain the stages in taxonomic procedures - gamma taxonomy, Explain the st...

Explain the stages in taxonomic procedures - Gamma Taxonomy This phase of taxonomy is also called biological taxonomy and is concerned with the study of speciation. It is inclu

Mitochondria, MITOCHONDRIA  (Singular-  MITOCHONDRION) These are cons...

MITOCHONDRIA  (Singular-  MITOCHONDRION) These are conspicuous, hollow  sac liked  cell organelles found in all eukaryotic  cells except  mature  red  blood  corpuscles RBC s

Define epithelial tissue, Epithelial tissue the cells in animals which are...

Epithelial tissue the cells in animals which are closely packed in either single or multiple layers, and which cover internal and external surfaces both of the animal body. It is

Explain the life history of lycophytes, Explain the Life History of Lycophy...

Explain the Life History of Lycophytes? Lycophytes have two separate and distinct generations in their life history that alternate with each other. The gametophyte stage is tin

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