Anthesis is

Options

A. opening of flower bud
B. floral bud formation
C. stigma receptor
D. meiosis in spore mother cell.

Answer

**Step-by-Step Solution:**

1. **Understanding Anthesis**:
- Anthesis refers to a specific phase in the life cycle of a flowering plant. It is the period during which a flower bud opens and becomes functional.

2. **Definition of Anthesis**:
- The term "anthesis" can be defined as the opening of a flower bud. This is the moment when the flower is fully developed and ready for pollination.

3. **Duration of Anthesis**:
- Anthesis not only includes the act of opening but also encompasses the time from when the flower bud opens until it transitions into fruit formation. This process is crucial for the reproductive cycle of flowering plants.

4. **Analyzing Other Options**:
- **Floral Bud Formation**: This refers to the initial stage of flower development, which occurs before anthesis, so it is not the correct answer.
- **Stigma Receptor**: The stigma is part of the flower that receives pollen; this process occurs after anthesis during pollination, making it incorrect as a definition of anthesis.
- **Meiosis in Spore Mother Cell**: This is a process that occurs in the reproductive parts of the flower after anthesis, thus it does not define anthesis.

5. **Conclusion**:
- Based on the definitions and analysis of the options, the correct answer to the question "Anthesis is" is **the opening of a flower bud**.

**Final Answer**: Anthesis is the opening of a flower bud.

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