According to potassium pump theory of Levitt

Options

A. Starch is incompetely oxidized to PEP during night
B. Malic acid dissociates into malate ion and protons in the subsidiary cells .
C. Movement of `H^(+)` ions from guard cell to subsidiary cell is active
D. Potassium malate decreases the OP of guard celll during day

Answer

**Step-by-Step Text Solution:**

1. **Understanding the Potassium Pump Theory**: The potassium pump theory, proposed by Levitt, explains the mechanism of stomatal movement in plants, particularly focusing on the role of potassium ions (K+) in guard cells.

2. **Starch Oxidation**: According to this theory, during the night, starch stored in the guard cells is completely oxidized to phosphoenolpyruvate (PEP). This process is crucial as it provides the necessary energy for subsequent reactions.

3. **Dissociation of Maleic Acid**: The theory states that maleic acid dissociates into maleate ions and protons (H+) in the guard cells. This dissociation is important for the movement of ions across the cell membranes.

4. **Active Transport of Hydrogen Ions**: The hydrogen ions (H+) are actively transported from the guard cells to the surrounding subsidiary cells. This active transport is essential for maintaining the osmotic balance and is facilitated by energy expenditure in the form of ATP.

5. **Decrease in Osmotic Potential**: As the potassium maleate concentration decreases in the guard cells, the osmotic potential (OP) of these cells also decreases. This decrease in osmotic potential is crucial for the opening and closing of the stomata.

6. **Role of Potassium Ions**: The accumulation of potassium ions (K+) inside the guard cells leads to turgor pressure changes, which cause the guard cells to swell and the stomata to open. Conversely, when potassium ions leave the guard cells, the stomata close.

7. **Stomatal Function**: Stomata are small openings primarily found on the leaves of plants, responsible for gas exchange (CO2 and O2) and transpiration (water vapor loss). The potassium pump theory explains how these processes are regulated by the movement of ions.

8. **Surrounding Cells**: The guard cells are surrounded by subsidiary cells, which play a supportive role in the functioning of the stomata. The interaction between these cells is vital for the regulation of stomatal opening and closing.