Anthesis is a phenomenon which refers to

Options

A. reception of pollen by stigma
B. formation of pollen
C. development of anther
D. opening of flower bud

Answer

**Step-by-Step Text Solution:**

1. **Understanding Anthesis**: Anthesis is a specific phenomenon that occurs during the flowering period of plants. It is important to recognize that this term is associated with the life cycle of flowering plants.

2. **Identifying the Correct Definition**: The primary characteristic of anthesis is the opening of the flower bud. This process is crucial as it marks the transition from a closed bud to a fully opened flower, allowing for reproduction.

3. **Functional Changes During Anthesis**: When the flower bud opens, several functional changes occur:
- The **extension of the style**, which is necessary for the reception of pollen.
- The **maturation of stamens**, which are the male reproductive parts of the flower.
- There may also be a **color change** in the flower, which can attract pollinators.

4. **Evaluating the Options**: Given the options:
- Reception of pollen by stigma: This occurs after anthesis.
- Formation of pollen: This occurs prior to anthesis.
- Development of anther: This is related to the growth phase before anthesis.
- Opening of flower bud: This directly describes anthesis.

5. **Conclusion**: Based on the definition and the functional changes that occur, the correct answer to the question "Anthesis is a phenomenon which refers to" is the **opening of flower bud**.

**Final Answer**: Anthesis refers to the opening of flower bud (Option D).

---