Question

Describe in sequence the events that lead to the development of a 3-celled pollen grain from microspore mother cell in angiosperms.

Answer 1

 

Pollen grain (male gametophyte) 

(i) The pollen grains represent the first cell of male gametophytes. 

(ii) A pollen grain has a two-layered wall namely, 

(a) Exine 

(b) Intine 

Exine: it is the hard outer layer which is made up of sporopollenin. 

Intine : 

(i) It is the inner, thin and continuous layer which is made up of cellulose and Pectin. 

(ii) A mature pollen grain contains two cells namely, 

(c) Vegetative cell 

(d) Generative cell 

Vegetative cell  : 

It is bigger ceil having abundant food reserve and a large irregularly shaped nucleus. 

Generative cell : 

(i) It is small cell that floats in the cytoplasm of the vegetative cell. 

(ii) It is spindle-shaped with dense cytoplasm and a nucleus.

1.  The pollen grains are shed at the 2-celled stage in Flowering Plants.

2.  ln other plants, the generative cell divides mitotically to give rise to the two male Sometimes before pollen grains are shed in 3-celled stage. 

3.  Once they are shed, pollen grains have to land on the stigma before they lose viability.

Answer 2

Answer:

Pollen grain (male gametophyte)

(i) The pollen grains represent the first cell of male gametophytes.

(ii) A pollen grain has a two-layered wall namely,

(a) Exine

(b) Intine

Exine: it is the hard outer layer which is made up of sporopollenin.

Intine :

(i) It is the inner, thin and continuous layer which is made up of cellulose and Pectin.

(ii) A mature pollen grain contains two cells namely,

(c) Vegetative cell

(d) Generative cell

Vegetative cell  :

It is bigger ceil having abundant food reserve and a large irregularly shaped nucleus.

Generative cell :

(i) It is small cell that floats in the cytoplasm of the vegetative cell.

(ii) It is spindle-shaped with dense cytoplasm and a nucleus.

1.  The pollen grains are shed at the 2-celled stage in Flowering Plants.

2.  ln other plants, the generative cell divides mitotically to give rise to the two male Sometimes before pollen grains are shed in 3-celled stage.

3.  Once they are shed, pollen grains have to land on the stigma before they lose viability.

Explanation: