PRE-POLLINATION DEVELOPMENT

Pollen grain or microspore is the first cell of male gametophyte and represents immature male gametophyte .

The development of male gametophyte starts inside the microsporangia .

The nucleus of  the pollen grain or microspore divides mitotically to form a vegetative nucleus or tube nucleus and a generative nucleus .

The nuclear division is followed by the cytoplasmic division forming a small generative cell and a large vegetative or tube cell .

The generative cell contains a callose layer which separates the cell from the pollen grain wall. But at later stage the callose dissolves and this naked generative cell comes to lie freely in the cytoplasm of the tube cell.

The tube cell has a vacudated cytoplasm which is rich in the starch protin and fats.

At this stage the pollen grain is 2 called and in most of the cases the pollen grain is discharged from the anther at 2-called stage.