Question

In a male gametophyte, the chromosomal number of generative nucleus is ---(A) ---and tube nucleus is (B).​

Answer 1

Pollen grain or the male gametophyte is formed from pollen mother cells through microsporogenesis and microgametogenesis. Each pollen mother cell (PMC) divide by meiosis to form four haploid microspores (this process is called microsporogenesis). Each microspore then develops into pollen grain (this process is called mocrogametogenesis).

Each microspore divides mitotically to form two cells: a large Vegetative cell and a small Generative cell. The generative cell resides within the cytoplasm of the vegetative cell. Later, the generative cell divides to form two sperm cells (i.e. male gametes or the male nuclei). At this stage, pollen grains are said to be 3-celled. If the generative cell divides inside the pollen tube, to form two male gametes the pollen is said to be liberated at 2-celled stage.

Thus, a mature pollen grain will always have 2 nuclei , whether liberated at 2-celled or 3-celled stage.

So, the correct answer is B.

Answer 2

Answer:

In a male gametophyte, the chromosomal number of generative nucleus is 2- celled and tube nucleus is 3- celled is the correct answer.

Explanation:

Through microsporogenesis and microgametogenesis, pollen grains or male gametophytes are generated from pollen mother cells. Meiosis divides each pollen mother cell (PMC) into four haploid microspores (this process is called microsporogenesis). Each microspore then matures into a pollen particle (this process is called mocrogametogenesis).

                Each microspore splits into two cells via mitosis: a large Vegetative cell and a tiny Generative cell.

• The vegetative cell's cytoplasm contains the generative cell.

• The generative cell then splits to generate two sperm cells (i.e. male gametes or the male nuclei).

Pollen grains are considered to be three-celled at this stage. The pollen is considered to be freed at the 2-celled stage if the generative cell splits inside the pollen tube to create two male gametes.

                 As a result, whether freed at the 2-celled or 3-celled stage, a mature pollen grain will always have two nuclei.

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