Name the cells that control the opening of the stomata.

Name the cells that control the opening of the stomata.

• A. Mesophyll cells
• B. Guard cells
• C. Epidermal cells
• D. Phloem cells

Answer: (B)

Guard cells are the cells that control the opening of the stomata. They come in pairs around each stomatal pore and regulate pore size by changing their turgor pressure. When guard cells accumulate ions like potassium and other solutes, water follows by osmosis, the cells swell, and the pore opens. Light—especially blue light—activates ion pumps that promote this ion uptake, enabling opening. Under water stress, ions exit the guard cells, water leaves, and the pore closes to reduce water loss. The other leaf cells don’t regulate the pore: mesophyll cells carry out photosynthesis inside the leaf, epidermal cells form the outer surface, and phloem cells transport sugars. So the opening and closing of the stomatal pore are controlled by the guard cells.

Guard cells are the cells that control the opening of the stomata. They come in pairs around each stomatal pore and regulate pore size by changing their turgor pressure. When guard cells accumulate ions like potassium and other solutes, water follows by osmosis, the cells swell, and the pore opens. Light—especially blue light—activates ion pumps that promote this ion uptake, enabling opening. Under water stress, ions exit the guard cells, water leaves, and the pore closes to reduce water loss. The other leaf cells don’t regulate the pore: mesophyll cells carry out photosynthesis inside the leaf, epidermal cells form the outer surface, and phloem cells transport sugars. So the opening and closing of the stomatal pore are controlled by the guard cells.