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  • (a) Where is microsporangium located in an angiosperm? State the functions of tapetum and the other three layers of microsporangium. (b) Describe the structure of the male gametophyte produced as a result of microsporogenesis. (c) State t

(a) Where is microsporangium located in an angiosperm? State the functions of tapetum and the other three layers of microsporangium.
(b) Describe the structure of the male gametophyte produced as a result of microsporogenesis.
(c) State the functions of each part of the male gametophyte.

 

 

 

 
 
 
 
 

Answers (1)

a) The microsporangium is located in the lobe of the anther.
Tapetum nourishes the developing pollen grains. Cells of the tapetum possess dense cytoplasm and generally have more than one nucleus.
Other three layers of microsporangium are- epidermis, endothecium, middle layers
They perform the function of protection and help in dehiscence of anther to release the pollen.

b) The pollen grains represent the male gametophytes. Structure of male gametophyte-
1. Pollen grains are generally spherical measuring about 25-50 micrometers in diameter.
2. It has a prominent two-layered wall. The hard outer layer called the exine which is made up of sporopollenin.
3. Pollen grain exine has prominent apertures called germ pores where sporopollenin is absent.
4. The inner wall of the pollen grain is called the intine.
5. The cytoplasm of the pollen grain is surrounded by a plasma membrane.
6. When the pollen grain is mature it contains two cells, the vegetative cell, and the generative cell.

c) Functions of each part of male gametophyte-
1. The hard outer layer called the exine is made up of sporopollenin which is one of the most resistant organic material known. It can withstand high temperatures and strong acids and alkali. No enzyme that degrades sporopollenin is so far known.
2. Pollen grain exine has prominent apertures called germ pores where sporopollenin is absent. Pollen grains are well preserved as fossils because of the presence of sporopollenin.
3. The inner wall of the pollen grain is called the intine. It is a thin and continuous layer made up of cellulose and pectin.
4. When the pollen grain is mature it contains two cells, the vegetative cell, and the generative cell. The vegetative cell is bigger, has abundant food reserves and a large irregularly shaped nucleus. The generative cell is small and floats in the cytoplasm the vegetative cell. It is spindle-shaped with dense cytoplasm and a nucleus.

Posted by

Priyanka Kumari

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