Opening and Closing of Stomata
When conditions favor the opening of the stomata (e.g., high light intensity and high humidity), the proton pump pushes protons (H+) out of the guard cells. This means that the electrical potential of the cells becomes more and more negative. To maintain this internal negative voltage so that potassium ions are not trapped, negative ions balance the potassium influx. In some cases, chloride ions enter the cells. This increases cell volume and turgor pressure. Then, because of rings of cellulose microfibrils that prevent the width of the guard cells from swelling, and thus only allow the extra turgor pressure to elongate the guard cells, creating an open pore through which gas can diffuse.
When the roots begin to sense a water shortage in the soil, abscisic acid (ABA) is released. ABA binds to receptor proteins in the guard cells’ plasma membrane and cytosol, which first raises the pH of the cytosol of the cells and cause the concentration of free Ca2+ to increase in the cytosol. This causes the chloride (Cl−) and organic ions to exit the cells. Second, this stops the uptake of any further K+ into the cells and, subsequently, the loss of K+. The loss of these solutes causes an increase in water potential, which results in the diffusion of water back out of the cell by osmosis. This makes the cell plasmolyzed, which results in the closing of the stomatal pores.
Stomata with Diagram, Structure, Types and Mechanism of Stomata
Stomata are tiny openings or pores found on the surfaces of plant leaves, stems, and other green parts. They play an important role in gas exchange, allowing plants to take in carbon dioxide for photosynthesis and release oxygen and water vapor. Stomata are surrounded by specialized guard cells that can open and close to regulate the rate of gas exchange and control water loss through transpiration.
Table of Content
- Stomata Definition
- What is Stomata?
- Diagram of Stomata
- Characteristics of Stomata
- Structure of Stomata
- Types of Stomata
- Opening and Closing of Stomata
- Functions of Stomata