[A]: The movement of ions from endodermis to xylem elements is an active process.
[R]: It requires the involvement of metabolic energy that comes from respiration.

Options

A. If both A and R are true and R is the correct explanation of A
B. If both A and R are true but R is not the correct explanation of A
C. If A is true and R is false
D. If both A and R are false

Answer

To solve the question regarding the assertion and reason related to the movement of ions from the endodermis to xylem elements, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that the movement of ions from the endodermis to xylem elements is an active process.
- Active transport is a biological process that requires energy to move substances against their concentration gradient.

2. **Understanding the Endodermis**:
- The endodermis is the innermost layer of the cortex in plant roots.
- It acts as a selective barrier to regulate the flow of water and nutrients into the vascular system.

3. **Role of the Casparian Strip**:
- The endodermis contains a structure called the Casparian strip, which is made of hydrophobic substances.
- This strip prevents passive flow of water and solutes, ensuring that substances must pass through the cell membranes of the endodermal cells.

4. **Movement of Ions**:
- The movement of ions from the endodermis to the xylem involves active transport mechanisms.
- This means that energy, typically derived from ATP generated through cellular respiration, is required to move ions against their concentration gradient.

5. **Understanding the Reason**:
- The reason states that this process requires metabolic energy that comes from respiration.
- Since active transport relies on energy, this statement supports the assertion.

6. **Conclusion**:
- Both the assertion and the reason are true.
- The reason correctly explains why the assertion is true, as the movement of ions indeed requires energy from respiration.

### Final Answer:
Both assertion and reason are true, and the reason is the correct explanation of the assertion.