Define the following terms
aestivation 

Explanation

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

1. **Definition of Aestivation**: Aestivation refers to the arrangement of sepals or petals in a floral bud concerning one another. It describes how these floral parts are positioned before the flower opens.

2. **Types of Aestivation**: There are four main types of aestivation:
- **Valvate**: In this type, the petals or sepals are arranged in such a way that they just touch each other at the edges without overlapping.
- **Twisted**: Here, the petals or sepals overlap each other in a spiral manner, with each succeeding petal or sepal being placed alternately.
- **Imbricate**: In imbricate aestivation, the petals or sepals overlap each other, but they do so in a way that they are not arranged spirally; rather, they overlap in a more irregular manner.
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