working of stomata / parts of stomata with functions
Answers
The opening and closing of stomata are regulated by factors such as light, plant carbon dioxide levels, and changes in environmental conditions. Humidity is an example of an environmental condition that regulates the opening or closing of stomata. When humidity conditions are optimal, stomata are open. Should humidity levels in the air around plant leaves decrease due to increased temperatures or windy conditions, more water vapor would diffuse from the plant into the air. Under such conditions, plants must close their stomata to prevent excess water loss.
Stomata open and close as a result of diffusion. Under hot and dry conditions, when water loss due to evaporation is high, stomata must close to prevent dehydration. Guard cells actively pump potassium ions (K +) out of the guard cells and into surrounding cells. This causes water in the enlarged guard cells to move osmotically from an area of low solute concentration (guard cells) to an area of high solute concentration (surrounding cells). The loss of water in the guard cells causes them to shrink. This shrinkage closes the stomatal pore.
When conditions change such that stomata need to open, potassium ions are actively pumped back into the guard cells from the surrounding cells. Water moves osmotically into guard cells causing them to swell and curve. This enlarging of the guard cells open the pores. The plant takes in carbon dioxide to be used in photosynthesis through open stomata. Oxygen and water vapor are also released back into the air through open stomata.