Answer: Calcium.
- A Potassium
- B Phosphorus
- C Calcium
- D Zinc
Correct answer: C. Calcium
Explanation: Calcium forms calcium pectate in the middle lamella of plant cell walls, cementing adjacent cells together. Calcium deficiency causes distorted and failed development of growing tips (terminal bud death).
Atmospheric N₂ is fixed into ammonia by nitrogen-fixing bacteria (protected from oxygen by leghaemoglobin in root nodules), converted to nitrate via nitrification for plant uptake, and eventually returned to the atmosphere as N₂ via denitrification, completing the cycle.
Concept context
Essential mineral elements, their roles and deficiency symptoms. Nitrogen fixation and soil nutrition.