Answer: Death of plant tissue (brown/black dead patches).
- A Yellowing of leaves from chlorophyll loss
- B Death of plant tissue (brown/black dead patches)
- C Increased growth from hormone imbalance
- D Localized rot confined only to roots
Correct answer: B. Death of plant tissue (brown/black dead patches)
Explanation: Necrosis means localized death of tissue, appearing as brown or black patches. Potassium deficiency typically causes necrosis at leaf margins and tips.
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.