According to scarth and sayre ,stomatal movement is governed by

Options

A. pH
B. enzymes
C. phosphorylation
D. `NADH_(2)` formation

Answer

**Step-by-Step Solution:**

1. **Understanding Stomatal Movement**: Stomata are small openings on the surfaces of leaves that allow for gas exchange. Their opening and closing are crucial for regulating water loss and gas exchange in plants.

2. **Reference to Scarth and Sayre**: In 1932, scientists Scarth and Sayre proposed a theory regarding the regulation of stomatal movement. They suggested that the interconversion between starch and sugar plays a significant role in this process.

3. **Role of Ions**: The movement of specific ions into and out of the guard cells surrounding the stomata is essential for their opening and closing. When ions accumulate in the guard cells, they create an osmotic pressure that causes water to flow into the cells, leading to turgor pressure that opens the stomata.

4. **Turgor Pressure**: Turgor pressure is the pressure exerted by the fluid inside the cell against the cell wall. It is vital for maintaining the structure and rigidity of the plant cells. When the guard cells are turgid, the stomata open; when they lose water and become flaccid, the stomata close.

5. **Influence of pH**: The pH level in the guard cells influences the movement of ions, which in turn regulates the opening and closing of the stomata. A change in pH can stimulate or inhibit the secretion of ions, affecting the osmotic balance and turgor pressure.

6. **Conclusion**: Based on the findings of Scarth and Sayre, the primary factor governing stomatal movement is the pH level, which controls the ion movement necessary for maintaining turgor pressure in the guard cells.

**Final Answer**: According to Scarth and Sayre, stomatal movement is governed by pH.

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