Question

In plants that shed pollen grain at two-celled condition, the generative cell divides and forms the two male gametes during the

• A. Growth of pollen tube in the style
• B. Entry of pollen tube in the synergid
• C. Entry of pollen tube in the ovule
• D. Growth of pollen tube in the stigma

Answer 1

The correct option is D Growth of pollen tube in the stigma

Pre-pollination development of male gametophyte

The male gametophyte starts its development while being within the microsporangium.

Its nucleus grows in size, moves to one end near the wall and divides to form a generative cell and a vegetative cell.

A callose cell wall develops around the cells which eventually dissolves and the generative cell floats in the cytoplasm of the vegetative cells.
The pollen may be released from the anther at this 2-cell stage.

Post pollination development of male gametophyte

Upon reaching the stigma, the pollen germinates after absorbing water and nutrients and develops a pollen tube as the vegetative or tube cell elongates.

The pollen tube consists of a tube nucleus and the generative cell which divides to form two male gametes during the formation of pollen tube on stigma tissue.

At this point, the pollen is fully mature and consists of 3 cells, a vegetative cell and two male gametes.

The tube nucleus of the vegetative cell guides the passage of the pollen tube through the style and to the egg apparatus.



Final answer

(C) Growth of pollen tube in the stigma