Chlorosis from magnesium deficiency

Steps:

• Observe symptoms: large leaves and good growth indicate no major water or light issues, but yellowing suggests nutrient problem.
• Recall yellowing (chlorosis) often ties to chlorophyll breakdown, linked to mineral deficiencies.
• Identify magnesium's role: it's central in chlorophyll molecule, so deficiency yellows leaves while growth continues.
• Rule out excesses or other lacks based on symptom match.

Why A is correct:

• Magnesium is a key component of chlorophyll (formula: C55H72MgN4O5), enabling photosynthesis; its deficiency causes interveinal yellowing without stunting growth.

Why the others are wrong:

• B: Lack of water causes wilting and stunted growth, not just yellowing in well-growing plants.
• C: Insufficient sunlight leads to pale, small leaves and leggy growth, not large healthy-sized yellow ones.
• D: Excess nitrate promotes lush green growth, not yellowing.

Final answer: A