Essential mineral ions in plant nutrition

Steps:

• Identify magnesium's primary role: it forms the core of chlorophyll, enabling photosynthesis.
• Identify nitrate's primary role: it provides nitrogen for synthesizing amino acids, which build proteins.
• Compare options: match magnesium to chlorophyll and nitrate to amino acids.
• Eliminate mismatches: select the option aligning with both roles.

Why D is correct:

• Chlorophyll's structure includes a magnesium ion at its center (formula: C55H72MgN4O5), while nitrates (NO3-) are reduced to ammonia for amino acid synthesis via nitrogen assimilation.

Why the others are wrong:

• A: Magnesium does not synthesize fatty acids; those derive from carbon chains.
• B: Nitrate ions do not make chlorophyll; magnesium does that.
• C: Nitrate ions do not make cellulose; cellulose is a carbohydrate from CO2 fixation.

Final answer: D