The germination of pollen grain up to the formation of male gametophyte involves several steps:

1. Pollen Grain Maturation: The pollen grain, which is the male gametophyte, matures in the anther of the flower. It has a hard protective outer layer called the exine, and a thin, inner layer called the intine.

2. Pollination: The mature pollen grain is transferred from the anther to the stigma of the same or a different flower. This process is called pollination.

3. Germination of Pollen Grain: Once the pollen grain lands on a receptive stigma, it begins to germinate. A pollen tube emerges from the pollen grain and starts to grow down through the tissues of the stigma and style towards the ovary.

4. Growth of Pollen Tube: The growth of the pollen tube is guided by chemical signals from the ovary. The tube grows by a process of tip extension, with new material being added to the tip of the tube, while the rest of the tube remains the same.

5. Formation of Male Gametophyte: Inside the pollen tube, two sperm cells are formed. These are the male gametes. The pollen tube carries these sperm cells down into the ovary.

6. Fertilization: Once the pollen tube reaches the ovary, it penetrates one of the ovules. The two sperm cells are released from the pollen tube. One sperm cell fertilizes the egg cell to form a zygote, which will develop into an embryo. The other sperm cell fuses with two polar nuclei to form the endosperm, which will nourish the developing embryo.

7. Formation of Seed: After fertilization, the ovule develops into a seed, and the ovary develops into a fruit. The male gametophyte has completed its role in the life cycle.

Question

The germination of pollen grain up to the formation of male gametophyte involves several steps:

1. Pollen Grain Maturation: The pollen grain, which is the male gametophyte, matures in the anther of the flower. It has a hard protective outer layer called the exine, and a thin, inner layer called the intine.

2. Pollination: The mature pollen grain is transferred from the anther to the stigma of the same or a different flower. This process is called pollination.

3. Germination of Pollen Grain: Once the pollen grain lands on a receptive stigma, it begins to germinate. A pollen tube emerges from the pollen grain and starts to grow down through the tissues of the stigma and style towards the ovary.

4. Growth of Pollen Tube: The growth of the pollen tube is guided by chemical signals from the ovary. The tube grows by a process of tip extension, with new material being added to the tip of the tube, while the rest of the tube remains the same.

5. Formation of Male Gametophyte: Inside the pollen tube, two sperm cells are formed. These are the male gametes. The pollen tube carries these sperm cells down into the ovary.

6. Fertilization: Once the pollen tube reaches the ovary, it penetrates one of the ovules. The two sperm cells are released from the pollen tube. One sperm cell fertilizes the egg cell to form a zygote, which will develop into an embryo. The other sperm cell fuses with two polar nuclei to form the endosperm, which will nourish the developing embryo.

7. Formation of Seed: After fertilization, the ovule develops into a seed, and the ovary develops into a fruit. The male gametophyte has completed its role in the life cycle.

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