IMO Practice Test — Mineral Nutrition
6 Questions • 15 min • Olympiad level
15:00
Question 1 of 6
A plant grown in a complete nutrient solution but with nitrogen removed shows yellow, stunted growth. This shows nitrogen is:
Essential and irreplaceable
Not needed
A micronutrient
Only decorative
Explanation: Removing only nitrogen causes deficiency, proving it is essential with a specific role.
Question 2 of 6
Deficiency of an immobile element such as calcium shows first in young leaves because the element:
Cannot be moved from old leaves to new growth
Is moved to old leaves
Is not needed by young leaves
Evaporates
Explanation: Immobile elements stay put, so new growth runs short first.
Question 3 of 6
A farmer alternates a wheat crop with a bean (legume) crop. The main benefit is that the legume:
Replenishes soil nitrogen via Rhizobium
Removes all minerals
Stops photosynthesis
Acidifies the soil permanently
Explanation: Legume root nodules fix nitrogen, restoring fertility for the next crop.
Question 4 of 6
Although needed in tiny amounts, a micronutrient like molybdenum is still essential because:
Its absence still prevents normal growth/completion of the life cycle
It is a macronutrient
It replaces nitrogen
It is not used at all
Explanation: Essentiality is about having a specific irreplaceable role, not the quantity needed.
Question 5 of 6
Both iron and magnesium deficiencies cause chlorosis, yet they differ because magnesium is part of chlorophyll while iron is needed to:
Synthesise chlorophyll (it is not part of it)
Form the cell wall
Open stomata
Fix nitrogen
Explanation: Mg is a structural part of chlorophyll; Fe is needed for its synthesis but is not part of the molecule.
Question 6 of 6
In a Rhizobium–legume association, the plant benefits from fixed nitrogen and the bacterium benefits from food and shelter. This relationship is:
Symbiosis (mutualism)
Parasitism
Competition
Predation
Explanation: Both partners gain, making it a mutualistic symbiosis.