Which is not a true statement regarding macronutrients ?

Options

A. Forms plant structure
B. Usually become toxic in excess
C. No role in electron transfer
D. Develop osmotic potential

Answer

To determine which statement is not true regarding macronutrients, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding Macronutrients**:
- Macronutrients are essential elements required by plants in large amounts. They include carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur.
- They play critical roles in the structure and function of plants, contributing to building blocks like proteins, carbohydrates, and nucleic acids.

2. **Evaluating Each Statement**:
- **Statement 1: "Forms plant structure"**:
- This statement is true because macronutrients are indeed part of the structural components of plants.

- **Statement 2: "Usually become toxic in excess"**:
- This statement is not true for macronutrients. While they are required in large amounts, they do not typically become toxic at high levels. This is more applicable to micronutrients, which can be toxic in excess.

- **Statement 3: "No role in electron transfer"**:
- This statement is true. Macronutrients do not play a direct role in electron transfer; this function is primarily associated with micronutrients like iron.

- **Statement 4: "Develop osmotic potential"**:
- This statement is also true. Macronutrients such as potassium, calcium, and magnesium are important for maintaining osmotic potential in plants.

3. **Conclusion**:
- The statement that is not true regarding macronutrients is **"Usually become toxic in excess"**. This is the correct answer to the question.

### Final Answer:
The statement that is not true regarding macronutrients is: **"Usually become toxic in excess."**

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