Answer: It activates enzymes and is essential for water splitting in photosynthesis (oxygen-evolving complex).
- A It forms the primary structural protein backbone found within the rigid plant cell wall in most cases
- B It activates enzymes and is essential for water splitting in photosynthesis (oxygen-evolving complex)
- C It functions mainly as a long-term storage molecule for excess plant carbohydrate reserves under typical conditions
- D It is sometimes thought to directly control the overall rate of root cell elongation alone according to standard textbooks
Correct answer: B. It activates enzymes and is essential for water splitting in photosynthesis (oxygen-evolving complex)
Explanation: Manganese activates many enzymes (decarboxylases, dehydrogenases) and is essential for the oxygen-evolving complex (OEC) of Photosystem II that splits water, releasing O<sub>2</sub>. Deficiency causes interveinal chlorosis similar to iron deficiency.
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.