CAPF AC 2022 Q17: Science & Technology – Biology
Depending on the requirements, plant nutrients are classified as micronutrients and macronutrients. Which one of the following is an example of a macronutrient?
- (a) Manganese
- (b) Copper
- (c) Magnesium
- (d) Chlorine
Answer: (c) Magnesium
Explanation
Macronutrients and micronutrients of plants
How to think: macro means needed in large amounts.
Micro means needed in tiny amounts.
Learn the six macronutrients taken from the soil; everything else in the options is a micronutrient.
| Group | Nutrients |
|---|---|
| From air and water | Carbon, oxygen, hydrogen |
| Macronutrients from soil | Nitrogen, phosphorus, potassium, calcium, magnesium, sulphur |
| Micronutrients from soil | Iron, manganese, boron, zinc, copper, molybdenum, chlorine |
Why magnesium is needed in bulk: it is the central atom of chlorophyll.
Without it leaves turn yellow, a condition called chlorosis.
Answer: (c) Magnesium.
Why each option is right or wrong
- (a) Incorrect. Manganese is needed only in traces; it is a micronutrient.
- (b) Incorrect. Copper is a micronutrient.
- (c) CORRECT. Magnesium is a macronutrient and forms the centre of chlorophyll.
- (d) Incorrect. Chlorine is a micronutrient.
Key point
NCERT Class IX: 16 nutrients; air gives C and O, water gives H, soil gives 13. Macronutrients: N, P, K, Ca, Mg, S. Micronutrients: Fe, Mn, B, Zn, Cu, Mo, Cl.
Remember
Macronutrients: N, P, K, Ca, Mg, S.
Common mistakes
- Mixing up magnesium (macro) with manganese (micro) because the names are alike.
- Thinking chlorine is a macronutrient because it sounds like chlorophyll.
- Forgetting that calcium, magnesium and sulphur are macronutrients along with N, P and K.
Exam tip
Educated guess: magnesium sits at the heart of chlorophyll, the pigment present in every green leaf. Something that common must be needed in large amounts.
Sources
- NCERT Class IX Science — Improvement in Food Resources (nutrient management)
- NCERT Class XI Biology — Mineral Nutrition