Importance of microelements was recognised late due to

Options

A. their toxicity
B. presence as contaminants in macronutrients
C. negligible role played by them in plant physiology
D. leakage from roots.

Answer

**Step-by-Step Solution:**

1. **Understanding Microelements**: Microelements, also known as micronutrients, are essential nutrients required by plants in small quantities. They include elements like iron, manganese, zinc, copper, molybdenum, and boron.

2. **Historical Context**: The recognition of the importance of microelements in plant nutrition occurred later than that of macronutrients (such as nitrogen, phosphorus, and potassium). This delay can be attributed to several factors.

3. **Analyzing the Options**:
- **Option A (Their toxicity)**: While some microelements can be toxic in high concentrations, this is not the primary reason for the late recognition of their importance.
- **Option B (Presence of contaminants in micronutrients)**: This option suggests that contaminants in micronutrients hindered their recognition, but this is not a widely accepted reason.
- **Option C (Negligible role played by them in plant physiology)**: Initially, it was believed that microelements played a negligible role compared to macronutrients, which contributed to the delay in their recognition.
- **Option D (Leakage from roots)**: This option does not directly relate to the recognition of microelements.

4. **Correct Answer**: The most appropriate answer is **Option B (Presence of contaminants in macronutrients)**. The presence of contaminants in the analysis of macronutrients may have overshadowed the importance of microelements, leading to a delayed recognition of their significance in plant nutrition.

5. **Conclusion**: The importance of microelements was recognized late primarily due to the presence of contaminants in macronutrients, which diverted attention away from the essential roles that microelements play in plant physiology.

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