Mark out the number of incorrect statement/s:
[I] Some essential elements can alter the osmotic potential of a cell.
[II] Nitrogen is required by the meristematic tissue and the metabolically active cells only.
[III] `Mg^(2+)` is needed by several respiratory enzymes.
[IV] Mo is essential for the water-splitting reaction in photosynthsis, a reaction that leads to oxygen evolution.
[V] Sulphur is the main constituent of several coenzymes, vitamins (thiamine, biotin, coenzyme-A) and ferrodoxin.

Options

A. Two
B. Three
C. Four
D. Five

Answer

To determine the number of incorrect statements from the given options, let's analyze each statement one by one.

**Step 1: Analyze Statement I**
- Statement: "Some essential elements can alter the osmotic potential of a cell."
- Analysis: This statement is true. Essential elements like potassium (K+) play a significant role in maintaining the osmotic potential and turgidity of cells.

**Step 2: Analyze Statement II**
- Statement: "Nitrogen is required by the meristematic tissue and the metabolically active cells only."
- Analysis: This statement is incorrect. While nitrogen is crucial for meristematic tissues and metabolically active cells, it is also needed by a variety of other cells in the plant for the synthesis of proteins, nucleic acids, and other important biomolecules.

**Step 3: Analyze Statement III**
- Statement: "Mg^(2+) is needed by several respiratory enzymes."
- Analysis: This statement is true. Magnesium ions are essential for the function of many enzymes, including those involved in respiration, such as Rubisco and phosphorylase.

**Step 4: Analyze Statement IV**
- Statement: "Mo is essential for the water-splitting reaction in photosynthesis, a reaction that leads to oxygen evolution."
- Analysis: This statement is true. Molybdenum is indeed involved in the water-splitting reaction in photosynthesis, particularly in the oxygen-evolving complex associated with photosystem II.

**Step 5: Analyze Statement V**
- Statement: "Sulphur is the main constituent of several coenzymes, vitamins (thiamine, biotin, coenzyme-A) and ferredoxin."
- Analysis: This statement is incorrect. While sulfur is a component of some coenzymes and vitamins, ferredoxin primarily contains iron as its main constituent, with sulfur being a secondary component.

**Final Evaluation: Count the Incorrect Statements**
- Incorrect Statements:
- Statement II: Incorrect
- Statement V: Incorrect

Thus, there are **2 incorrect statements** in total.

### Summary of Incorrect Statements:
- Statement II is incorrect because nitrogen is required by a broader range of cells, not just meristematic and metabolically active cells.
- Statement V is incorrect because the main constituent of ferredoxin is iron, not sulfur.

### Final Answer:
**There are 2 incorrect statements.**

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