In plants which of the following is required in minute quantities for growth?

1. Analyze the question The question asks which element a plant needs only in minute (very small) quantities for growth. These are called micronutrients or trace elements.

2. Explain the concept Plant mineral nutrients fall into two groups:

• Macronutrients (needed in large amounts): Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca), Magnesium (Mg), Sulphur (S)
• Micronutrients / trace elements (needed in tiny amounts): Iron (Fe), Manganese (Mn), Zinc (Zn), Copper (Cu), Boron (B), Molybdenum (Mo), Chlorine (Cl)

3. Solution, option by option

• A. Copper: a micronutrient. It is needed in tiny amounts for enzyme activity and photosynthesis. ✔
• B. Potassium: a macronutrient, needed in large amounts for enzyme activation and water balance. ✘
• C. Phosphorus: a macronutrient, needed in large amounts for ATP, DNA and root development. ✘
• D. Sodium: not generally considered essential for most plants. It is not a standard micronutrient in the JAMB syllabus. ✘

4. Answer Copper is the only option that is a recognized trace element essential for plant growth.

5. Exam tip Remember the macronutrients with the first letters of "C. HOPKINS CaFe Mg" (C, H, O, P, K, N, S, Ca, Fe, Mg). Anything not on the big list, such as Cu, Zn, Mn, B or Mo, is usually a trace element. In JAMB, when you see Cu, Zn, Mn, B, Mo or Fe, think "minute quantities."