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

What are some examples of parasitism, What are some examples of parasitism?...

What are some examples of parasitism? Classical instances are the parasites of humans (host), as the trypanosome that causes Chagas' disease, the HIV virus (AIDS), the bacteria

What are the major orders of placental mammals, Q. What are the major order...

Q. What are the major orders of placental mammals? What are a few representative species and distinguishing features of each of those orders? The orders into which placental ma

Vitamins and minerals requirement in diabetes, Q. Vitamins and minerals req...

Q. Vitamins and minerals requirement in diabetes? The recommendation of vitamins and minerals is the same as for general population. However, lower levels of magnesium are ass

, comparitive table to explain the differences between the animals in chor...

comparitive table to explain the differences between the animals in chordate classes

Becoming online tutor, how can i work with u as an online biology tutor?

how can i work with u as an online biology tutor?

Tissue, Why lymph is called the middle man of our body?

Why lymph is called the middle man of our body?

How do chloroplasts multiply, How do chloroplasts multiply? Like mitoch...

How do chloroplasts multiply? Like mitochondria chloroplasts have their own DNA, RNA and ribosomes and they self-replicate through binary division.

Exercises and ambulation for cardiac patients, Exercises and ambulation ...

Exercises and ambulation Continue taking all exercises taught in the hospital. Steam inhalation may be continued. Walk on levelled space first, gradually increase the dista

Amoebae - protozoan, Amoebae - Protozoan Amoebae may be naked or enclo...

Amoebae - Protozoan Amoebae may be naked or enclosed in tests or shells. The marine, freshwater and parasitic naked amoebae have large commonly tubular lobopodia or fine strap

What is reflexive memory, What is reflexive memory? Reflexive memory re...

What is reflexive memory? Reflexive memory relies on the cerebellum and amygdala. Compare among aerobic respiration and anaerobic respiration. Aerobic respiration happens in th

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