The only way for water and solute molecules to enter the vascular cylinder is

Options

A. Apoplastic pathway
B. Symplastic pathway
C. Osmosis
D. Facilitated diffusion

Answer

To solve the question regarding the only way for water and solute molecules to enter the vascular cylinder, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Vascular Cylinder**: The vascular cylinder, also known as the stele, is the central part of a root or stem that contains the xylem and phloem tissues responsible for the transport of water, nutrients, and food.

2. **Identify Pathways for Water and Solute Movement**: There are several pathways through which water and solutes can move in plants:
- **Apoplastic Pathway**: Movement through the cell walls and intercellular spaces without crossing the plasma membrane.
- **Simplastic Pathway**: Movement through the cytoplasm of the cells, which involves crossing the plasma membrane and moving from one cell to another via plasmodesmata.
- **Osmosis**: A specific type of diffusion where water moves across a selectively permeable membrane.
- **Facilitated Diffusion**: Movement of molecules across a membrane via specific transport proteins.

3. **Focus on the Endodermis**: The endodermis is the innermost layer of the cortex in roots and acts as a selective barrier. It regulates the entry of water and solutes into the vascular cylinder.

4. **Determine the Correct Pathway**: The simplastic pathway is the primary route for water and solute molecules to enter the vascular cylinder, especially as they pass through the endodermis. This pathway allows for selective uptake and is crucial for maintaining the plant's internal environment.

5. **Conclusion**: Based on the understanding of the pathways and the role of the endodermis, the correct answer to the question is:
- **Option B: Simplastic pathway**.