Iron is mainly required by plants for_________formation.

Analyze the question: The question asks what the plant mainly needs iron (Fe) for. This is about mineral nutrition in plants.

Explain the concept: Plants take up mineral elements as ions from the soil. Each one has a particular job:

• Nitrogen is needed for proteins, amino acids and nucleic acids.
• Magnesium is a central part of the chlorophyll molecule.
• Iron is not part of the chlorophyll molecule, but it is essential for chlorophyll synthesis. It is also a component of electron-carrier enzymes (such as cytochromes) in respiration and photosynthesis.
• Phosphorus is needed for nucleic acids, ATP and cell membranes.

Solution:

1. Iron deficiency leads to chlorosis, in which leaves turn yellow because chlorophyll cannot form properly.
2. Glucose is made by photosynthesis, not by a mineral directly. So B is out.
3. Protein formation mainly needs nitrogen and sulphur. So C is out.
4. "Nuclear" is not a sensible product, and nucleoproteins mainly need nitrogen and phosphorus. So D and E are out.
5. Chlorophyll formation is the classic textbook role of iron.

Answer: The correct option is **A.

Exam tip: Remember "Fe and Mg make chlorophyll go." Magnesium sits at the center of the chlorophyll molecule, and iron is needed to make it. If a question describes yellow leaves (chlorosis), think iron, magnesium or nitrogen deficiency.