explain the entire process of microgametogenesis with suitable labelled diagrams
Developmentof male gamete is called microgametogenesis.
Pollen grain is the first cell of the male gametophyte, which contains only one haploid nucleus.
It remains within the microsporangium during early stages of development.
The cell undergoes unequal division and forms a small generative cell and a large vegetative or tube cell. The generative cell remains lying at one corner of the spore wall.
Later, it gets detached and becomes ellipsoid or fusiform in shape and remains suspended in the cytoplasm of the vegetative cell (2-celled stage).
Later, the generative cell divides and gives rise to two ellipsoidal spherical cells.
The second division in which generative cell may divide either in the pollen grain or in the pollen tube which develops through germ pore after pollination.
The nucleus of the vegetative cell is commonly known as tube nucleus.
Finally the tube nucleus remains within spore or may enter the pollen tube.
Later, it gets degenerated completely.