Definitions for "Guard cells"
The guard cells are are two crescent-shaped cells on either side of the pore of a stoma in the epidermis of the stem or leaf. By changing shape, the guard cells are able to cover and uncover the pore of the stoma and let oxygen out and carbon dioxide into the stem or leaf. Changes in turgor pressure is the mechanism by which the shape of the guard cell is altered so as to cover and uncover the pore. DIAGRAMS: Stomata / Stomata PHOTOS: Leaf Cross Section
Specialized cells, occurring usually in pairs that surround the stomata of a plant and aid in the control of the stomatal pore size.
paired, specialized, epidermal cells that contain chloroplasts and surround a stoma