The time taken for the development of two adjacent leaves is called .................. index.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the term used to describe the time taken for the development of two adjacent leaves. This indicates that we are looking for a specific index related to leaf development.

2. **Identifying the Index**: The relevant index that measures the time interval between the development of two adjacent leaves is known as the "Plastocoron Index."

3. **Defining Plastocoron Index**: The Plastocoron Index is specifically used to calculate the time interval between the emergence of two leaves from consecutive nodes on a plant. This index helps in understanding the growth pattern of a plant.

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