The youngest layer of secondary phloem in woody dicot stem is located

Options

A. Just outside to epidermis
B. Just outside to vascular cambium
C. Just inside to vascular cambium
D. Between periderm and primary cortex

Answer

To determine the location of the youngest layer of secondary phloem in a woody dicot stem, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of the Woody Dicot Stem**:
- The woody dicot stem consists of several layers, including the epidermis, cortex, vascular cambium, xylem, and phloem.

2. **Identify the Vascular Cambium**:
- The vascular cambium is a layer of meristematic tissue located between the xylem and phloem. It is responsible for the production of secondary xylem (wood) and secondary phloem.

3. **Locate the Secondary Phloem**:
- Secondary phloem is produced by the vascular cambium. The youngest layer of secondary phloem is formed just outside the vascular cambium.

4. **Differentiate Between Phloem Types**:
- There are two types of phloem: primary phloem (formed during primary growth) and secondary phloem (formed during secondary growth). The secondary phloem is located outside the vascular cambium, while the primary phloem is found further out.

5. **Eliminate Incorrect Options**:
- **Just outside the epidermis**: This is incorrect because the epidermis is the outermost layer, and secondary phloem is located deeper.
- **Inside the vascular cambium**: This is incorrect because the vascular cambium produces phloem outwardly.
- **Between periderm and primary cortex**: This is incorrect as the secondary phloem lies outside the vascular cambium and is not located between these two layers.

6. **Conclude the Correct Answer**:
- Therefore, the youngest layer of secondary phloem in a woody dicot stem is located just outside the vascular cambium.

### Final Answer:
The youngest layer of secondary phloem in a woody dicot stem is located **just outside the vascular cambium**.

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