How do potassium ions regulate the opening and closing of stomata?

Hint: The Small openings that are present on the epidermis of the leaf are called Stomata. Stomata can be seen using a light microscope. It can be found on the stems and other parts of some plants. There are thousands of stomata lying on the surface of leaves.

Complete answer:
The theory is called Potassium Ion Concentration Theory. According to this theory, the opening and closing of stomata depend on the production of potassium ion gradient. The average number of stomata on the surface of the leaf is about 300 per square mm.

Adenosine Triphosphate (ATP) that was produced during photosynthesis in the guard cells is later utilized to pump the potassium ions of the adjacent cells into guard cells. Guard cells contain chloroplasts and are bean-shaped. An increase in potassium(K) ion makes the guard cells hypertonic so that more water can enter inside the cells.

During this, the stomatal pore is opened. Closing is just an opposite phenomenon of opening as in closing the water is removed from the guard cells and they become flaccid. Potassium ions are removed from the cell. Stomatal pore closes due to this. The absence of light and the lowering rate of photosynthesis are the reasons for the closing down of stomatal pores. Stomata help in the transpiration and removal of excess water in the form of water vapour. At night stomatal pores close which prevent water from escaping.

Note: Stomata maintains the moisture balance by opening and closing according to the weather. During the process of photosynthesis, Stomata is the main centre for the uptake of carbon dioxide and the release of oxygen in the surroundings.