oldest part of phloem in a dicot stem is situated just

Options

A. outside vascular cambium
B. inner to primary cortex
C. inner to vascular cambium
D. between periderm and primary cortex.

Answer

To determine the location of the oldest part of the 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 consists of various layers, including the epidermis, cortex, vascular bundles, cambium, xylem, and phloem.

2. **Identify the Vascular Bundle**:
- Within the stem, there are vascular bundles that contain both xylem and phloem. The cambium layer separates the xylem from the phloem.

3. **Recognize the Role of Cambium**:
- The cambium is a layer of meristematic tissue that allows for secondary growth. It produces new layers of xylem and phloem as the plant grows.

4. **Understand Secondary Growth**:
- As the plant undergoes secondary growth, the cambium produces new phloem cells towards the outside and new xylem cells towards the inside. This means that older phloem cells will be pushed inward as new cells are formed.

5. **Locate the Oldest Phloem**:
- The oldest part of the phloem is located closest to the cambium, which is situated between the newly formed phloem and the older layers. As a result, the oldest phloem will be found just inside the cambium layer.

6. **Determine the Correct Position**:
- Given the options provided, the oldest part of the phloem in a dicot stem is situated just inside the primary cortex, which is the area between the cambium and the cortex.

### Final Answer:
The oldest part of the phloem in a dicot stem is situated just **inside the primary cortex**.

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