No, a stoma (plural: stomata) is not a single cell. A stoma is a pore, or tiny opening, found on the epidermis of leaves and other plant organs. It's composed of two specialized cells called guard cells. These guard cells regulate the opening and closing of the stoma, controlling gas exchange (like carbon dioxide intake and oxygen release) and water loss.
Understanding Stomata Structure and Function
-
Guard Cells: Two kidney-shaped guard cells surround each stomatal pore. These cells control the pore's size by changing their turgor pressure (internal water pressure). Increased turgor pressure causes the guard cells to swell and open the pore; decreased turgor pressure causes them to shrink and close the pore.
-
Stomatal Pore: The actual opening, the pore itself, is the space between the guard cells. This is where gas exchange occurs.
-
Subsidiary Cells (sometimes): Some stomata are surrounded by additional cells called subsidiary cells. These cells play a supporting role in stomatal function, but the guard cells are the primary players in regulating the pore.
Multiple sources confirm this structure:
- "Stomata are composed of a pair of specialized epidermal cells referred to as guard cells."
- "The pore consists of two cells — each known as a guard cell. They can swell or shrink to open or close the pore, which is critical for..." (https://www.washington.edu/news/2018/05/07/stomata-the-plant-pores-that-give-us-life-arise-thanks-to-a-gene-called-mute-scientists-report/)
- "Two guard cells surround each stomatal pore, and changes in turgor pressure of the guard cells regulate the size of the pore aperture." (https://pmc.ncbi.nlm.nih.gov/articles/PMC3913439/)
Therefore, while guard cells are indeed individual cells, the stoma itself is a structure formed by these cells and the pore they create.