Which of the following is a micronutrient?

• A. Nitrogen
• B. Phosphorus
• C. Iron
• D. Potassium

Answer: (C)

The concept being tested is the difference between micronutrients and macronutrients in plants. Micronutrients are minerals needed in very small amounts but are essential for specific physiological processes. Iron is a micronutrient because plants require only trace amounts of it, yet it plays a critical role in enzyme function and chlorophyll production, helping with energy transfer in cells and overall photosynthesis. When iron is insufficient, young leaves often yellow between the veins due to impaired chlorophyll formation, even if other nutrients are adequate.

In contrast, nitrogen, phosphorus, and potassium are macronutrients, needed in much larger quantities for building amino acids, nucleic acids, energy molecules, and supporting growth. That’s why iron stands out as the micronutrient among the options.