Question

Which of the following elements regulates the opening and closing of stomata?

• A. N
• B. K
• C. S
• D. P

Hint:

Remember the role of K\(^+\) in stomatal regulation.
Key minerals: K for stomata, Mg for chlorophyll, P for ATP, N for proteins.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Stomata are pores on plant leaves that regulate gas exchange and water loss.
Their opening and closing is controlled by changes in the turgor pressure of guard cells.

Step 2: Key Approach:
This is a plant physiology question.
Identify the element involved in the osmotic regulation of guard cells.

Step 3: Detailed Explanation:
Stomatal movement is regulated by potassium ions (K\(^+\)).
When K\(^+\) ions are actively transported into the guard cells, the osmotic potential decreases,
and water enters the cells, causing them to become turgid and open the stomata.
Conversely, when K\(^+\) ions move out, the cells become flaccid, and stomata close.
Nitrogen (N) is a component of chlorophyll and proteins.
Sulfur (S) is needed for amino acids and vitamins.
Phosphorus (P) is involved in energy transfer and nucleic acid formation.
Thus, K is the correct answer.
Auxin and abscisic acid also play roles, but the ion primarily responsible is potassium.