Answer: Chlorosis (yellowing) especially in older leaves first.
- A Purple/red coloration from anthocyanin accumulation
- B Chlorosis (yellowing) especially in older leaves first
- C Death of growing tips and apical buds
- D Brown scorched margins on mature leaves
Correct answer: B. Chlorosis (yellowing) especially in older leaves first
Explanation: Nitrogen deficiency causes yellowing (chlorosis) starting in older leaves (nitrogen is mobile and moves to younger leaves). Growth is stunted. Nitrogen is a component of proteins and chlorophyll.
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.