Magnesium is an activator for

Options

A. ribulose bis-phosphate carboxylase oxygenase
B. phosphoenol pyruvate carboxylase
C. alcohol dehydrogenase
D. more than one

Answer

To solve the question "Magnesium is an activator for," we need to analyze the options provided and understand the role of magnesium in plant physiology.

### Step-by-Step Solution:

1. **Understanding Magnesium's Role**:
- Magnesium is an essential macronutrient for plants, meaning it is required in large quantities for their growth and development. It is absorbed in the form of magnesium ions (Mg²⁺).

2. **Functions of Magnesium**:
- Magnesium plays a crucial role in activating various enzymes involved in key biological processes, particularly in respiration and photosynthesis.

3. **Identifying the Enzymes**:
- The question provides several options:
- Ribulose bisphosphate carboxylase/oxygenase (Rubisco)
- Phosphoenolpyruvate carboxylase
- Alcohol dehydrogenase

4. **Analyzing Each Option**:
- **Ribulose bisphosphate carboxylase/oxygenase**: This enzyme is crucial in the Calvin cycle of photosynthesis and is known to require magnesium as an activator.
- **Phosphoenolpyruvate carboxylase**: This enzyme is also involved in photosynthesis and requires magnesium for its activity.
- **Alcohol dehydrogenase**: This enzyme does not require magnesium as an activator; instead, zinc acts as an activator for alcohol dehydrogenase.

5. **Conclusion**:
- Based on the analysis, magnesium acts as an activator for both ribulose bisphosphate carboxylase/oxygenase and phosphoenolpyruvate carboxylase. Therefore, the correct answer includes these two enzymes.

6. **Final Answer**:
- Magnesium is an activator for ribulose bisphosphate carboxylase/oxygenase and phosphoenolpyruvate carboxylase. The correct option is "more than one" (D).