How many gametes are produced in the pollen grain of a flowering plant before fertilization?

Analyze the question: The question asks how many gametes (male sex cells) are present in a pollen grain of a flowering plant before fertilization takes place.

Explain the concept: When a pollen grain forms in the anther, its nucleus divides by mitosis to give two nuclei:

1. Tube nucleus (vegetative nucleus): controls the growth of the pollen tube. It is not a gamete.
2. Generative nucleus: divides again by mitosis to form two male gametes.

This second division may happen inside the pollen grain, or in the pollen tube after the grain lands on the stigma.

Step-by-step solution:

1. The pollen grain starts with a single nucleus (microspore).
2. It divides into a tube nucleus and a generative nucleus.
3. The generative nucleus divides into two male gametes.
4. In double fertilization, one male gamete fuses with the egg cell to form the zygote (2n). The other fuses with the two polar nuclei to form the endosperm (3n).

This is why two male gametes are needed.

Possible confusion: Some students pick "one" because they think of one gamete fertilizing one egg. In flowering plants, however, two male gametes are involved because of double fertilization. Others pick "three" because they count the tube nucleus, but the tube nucleus is not a gamete.

Answer: Option B (two).

Exam tip: Remember "2 male gametes, 2 fusions": one fuses with the egg (zygote) and one with the polar nuclei (endosperm). Whenever you see "double fertilization" in angiosperms, think of the number two.