Which of the following get accumulated in the vacuoles of guard cells during stomatal opening ?

Options

A. Water , calcium and magnesium
B. Starch , potassium and chloride ions
C. Malate , sodium and potassium ions
D. Malate , potassium and chloride ions

Answer

To determine which substances accumulate in the vacuoles of guard cells during stomatal opening, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Guard Cells**: Guard cells are specialized cells that surround stomata (small openings on the leaf surface) and regulate their opening and closing. The movement of ions and water in these cells is crucial for stomatal function.

2. **Role of Potassium Ions (K+)**: During stomatal opening, potassium ions (K+) play a significant role. They are actively transported into the guard cells, leading to an increase in osmotic pressure.

3. **Hydrolysis of Starch**: The process begins with the hydrolysis of starch stored in the guard cells. This starch is broken down into simpler sugars, which are then converted into organic acids.

4. **Formation of Malate**: The organic acid produced, primarily oxalic acid, is further converted into malic acid. Malic acid is a weak acid that dissociates into malate ions and hydrogen ions (H+).

5. **Ion Exchange**: As malate ions accumulate in the guard cells, H+ ions are exchanged for K+ ions from the surrounding environment. This exchange is crucial for maintaining the charge balance and osmotic pressure within the guard cells.

6. **Accumulation of Substances**: Therefore, during stomatal opening, the substances that accumulate in the vacuoles of guard cells are primarily malate ions, potassium ions (K+), and chloride ions (Cl-).

7. **Conclusion**: Based on the above steps, the correct answer to the question is that malate, potassium ions, and chloride ions accumulate in the vacuoles of guard cells during stomatal opening.

### Final Answer:
The substances that accumulate in the vacuoles of guard cells during stomatal opening are **malate, potassium ions (K+), and chloride ions (Cl-)**.

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