What is the location of the oldest and youngest layers of secondary pholem in a dicot stem?

Explanation

To answer the question regarding the location of the oldest and youngest layers of secondary phloem in a dicot stem, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of a Dicot Stem**:
- A dicot stem has a vascular system that includes vascular bundles arranged in a ring form. Each vascular bundle consists of xylem and phloem.

2. **Identify the Role of Vascular Cambium**:
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