Magnesium Deficiency Impairs Chlorophyll Synthesis

Steps:

• Identify magnesium's biological role: it forms the core of chlorophyll molecules essential for photosynthesis.
• Recognize deficiency symptoms: reduced chlorophyll leads to chlorosis, where leaves lose green color.
• Evaluate options against known plant nutrition facts: match symptoms to mineral deficiencies.
• Confirm via elimination: only one option aligns with magnesium's function.

Why A is correct:

• Magnesium is the central atom in the chlorophyll molecule (C55H72MgN4O5), so its deficiency directly reduces chlorophyll production, causing yellowing leaves.

Why the others are wrong:

• B: Dark green leaves indicate excess nitrogen, not magnesium lack.
• C: Starch production decreases due to impaired photosynthesis from low chlorophyll.
• D: Wilting young leaves results from calcium deficiency, not magnesium.

Final answer: A