NEET BIOLOGY

Detailed explanation-1: -In 60% angiosperms, pollen grain is liberated at this two-celled stage. Thus, a mature pollen grain consists of 2 cells. In the remaining species, the generative cell divides mitotically to give rise to the two male gametes before pollen grains are shed (3-celled stage).

Detailed explanation-2: -In about 40% of the angiosperms, the generative nucleus undergoes mitosis and gives rise to 2 male gametes. The pollen grains are shed during this 3-celled stage.

Detailed explanation-3: -In most of the angiosperms pollen grains are shed at 2-celled staged, at this stage pollen grain has two cells called vegetative cell and generative cell. In some of the species before the shedding of pollen grain, generative cell divides mitotically to give rise to two male gametes.

Detailed explanation-4: -* Two male gametes and one vegetative cells are the three cells found in a pollen grain when it is shed at the three celled stage. Q.

Detailed explanation-5: -In 2-celled staged of pollen grains, each pollen grain contains vegetative cell and generative cell whereas in 3-celled stage, the generative cell undergoes meiotic division to form two sperm cells. In 2 celled-stage, generative cell divides in the pollen tube but not in a 3-celled stage.