In order to enter the stele, water and minerals must pass through:

Options

A. the apoplast
B. the casparian strip
C. endodermal cells
D. xylem vessels

Answer

To answer the question, "In order to enter the stele, water and minerals must pass through:", we will analyze the options provided and determine the correct pathway for water and minerals to enter the stele of a plant.

### Step-by-Step Solution:

1. **Understanding the Stele**:
- The stele is the central part of the root or stem that contains vascular tissues, which include xylem and phloem, and sometimes ground tissues. It is surrounded by the endodermis, which is the innermost layer of the cortex.

2. **Analyzing the Options**:
- **Option 1: Apoplast**: The apoplast pathway involves the movement of water and solutes through the cell walls and intercellular spaces. However, the endodermis contains the Casparian strip, which is impermeable to water, making this pathway ineffective for entering the stele.

- **Option 2: Casparian Strip**: The Casparian strip is a band of suberin (a waxy substance) found in the endodermal cell walls. It acts as a barrier to water and solutes, preventing them from passing through the cell walls and forcing them to enter the cells. Thus, this option cannot be correct as it does not allow passage into the stele.

- **Option 3: Endodermal Cells**: The endodermal cells are the innermost layer of the cortex and are crucial for regulating the entry of water and minerals into the stele. Water must pass through these cells to enter the stele, as they control the movement of substances into the vascular tissues.

- **Option 4: Xylem Vessels**: Xylem vessels are part of the stele and are responsible for transporting water and minerals. However, they are not the pathway that water and minerals take to enter the stele; rather, they are the destination for these substances after they have entered the stele.

3. **Conclusion**:
- Based on the analysis, the only viable option for water and minerals to enter the stele is through the **endodermal cells**. They allow the movement of water and minerals into the stele after passing through the Casparian strip.

### Final Answer:
In order to enter the stele, water and minerals must pass through **endodermal cells**.

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