Question

Accessory cells of stomata are reservoirs of________.

• A. $\text{Zn}^{++}$ions
• B. $\text{H}^{+}$ions
• C. $\text{K}^{+}$ions
• D. $\text{H}^{+}$ions and $\text{Cl}^{-}$ions

Hint:

Key idea: K$^{+}$ in $\rightarrow$ Water in $\rightarrow$ Stomata open K$^{+}$ out $\rightarrow$ Water out $\rightarrow$ Stomata close

Answer 1

The Correct Option is C

Concept: Stomatal opening and closing are regulated by the movement of ions, especially potassium ions, between guard cells and accessory cells.
• Accessory (subsidiary) cells act as storage sites for ions.
• $\text{K}^{+}$ ions move into guard cells during stomatal opening.
• This increases osmotic pressure, causing water to enter and stomata to open.

Step 1: Understand stomatal mechanism.
Opening of stomata involves active transport of $\text{K}^{+}$ ions into guard cells.

Step 2: Role of accessory cells.
Accessory cells serve as reservoirs from where $\text{K}^{+}$ ions are supplied to guard cells.

Step 3: Analyze options.
• (A) Zn$^{++}$: Not involved
• (B) H$^{+}$: Involved in proton pump, not stored
• (C) K$^{+}$: Correct
• (D) H$^{+}$ and Cl$^{-}$: Not primary reservoir Final Answer: Option (C)