Generative Nucleus in a Pollen Grain
The small nucleus in a pollen grain is known as the generative nucleus. The generative nucleus plays a crucial role in the process of pollination and fertilization in plants. Here is a detailed explanation of the generative nucleus and its functions:
Definition:
The generative nucleus is a small nucleus found within the pollen grain of a flowering plant. It is responsible for the formation of male gametes or sperm cells.
Functions:
1. Sperm Cell Formation: The generative nucleus divides mitotically to produce two sperm cells. These sperm cells are involved in the process of fertilization, where they fuse with the female gametes to form a zygote.
2. Pollen Tube Formation: After pollination occurs, the generative nucleus, along with the tube nucleus, helps in the formation of the pollen tube. The pollen tube is a long, slender structure that grows from the pollen grain towards the ovule, allowing the sperm cells to reach the embryo sac.
3. Double Fertilization: Once the pollen tube reaches the ovule, the generative nucleus divides again to release the two sperm cells. One sperm cell fuses with the egg cell to form the zygote, while the other sperm cell fuses with the polar nuclei to form the endosperm, which provides nourishment to the developing embryo.
In conclusion, the small nucleus in a pollen grain is called the generative nucleus. It is involved in the formation of male gametes, the growth of the pollen tube, and the process of double fertilization.