Iron is an essential nutrient in plants because it

Step 1: Analyze the question The question asks why iron (Fe) is an essential mineral nutrient in plants. Iron is a micronutrient, meaning plants need it in small amounts, but they cannot grow properly without it.

Step 2: Explain the concept Iron has these main roles in plants:

• It is needed for chlorophyll synthesis. Iron is not part of the chlorophyll molecule (magnesium is), but without iron the plant cannot make chlorophyll.
• It is part of enzymes and proteins involved in respiration and photosynthesis, such as cytochromes and ferredoxin.
• It is involved in protein/nitrogen metabolism, including nitrogen fixation enzymes.

The classic deficiency symptom is chlorosis, a yellowing of the leaves, especially the young ones, because chlorophyll cannot form.

Step 3: Check each option

• A. Aids in the formation of chlorophyll and proteins. Correct. This matches iron's role in chlorophyll synthesis and in protein-related enzymes.
• B. Helps in cell division. This is not iron's main role. It is more associated with nutrients like calcium, boron, and nitrogen.
• C. Protects the plants from pest attack. Potassium is more often linked to disease resistance, not iron.
• D. Fastens fruit maturation. This is linked to hormones like ethylene, and to nutrients such as phosphorus and potassium, not iron.

Step 4: Answer The correct option is A.

Exam tip: Link Fe with chlorophyll. If you see "yellowing of young leaves (chlorosis)", think iron (or magnesium for older leaves). A handy memory line: "No Iron, no green."