guard cell
specialized cell of leaf epidermis that regulates the size of a leaf stoma
Source: Noland, George B. 1983. General Biology, 11th Edition. St. Louis, MO. C. V. Mosby ...
guard cells -- Pair of cells which surround a stomate and regulate its size by altering their shape.
gymnosperm -- n. A plant that produces seeds, which are not enclosed; includes any seed plant that does not produce flowers.
Guard Cells
To facilitate gas exchange between the inner parts of leaves, stems, and fruits, plants have a series of openings known as stomata (singular stoma). Obviously these openings would allow gas exchange, but at a cost of water loss.
guard cell
A specialized epidermal plant cell that forms the boundaries of the stomata.
guttation ...
[edit] Guard cells
Stoma in a tomato leaf (microscope image)
Main article: Stoma ...
guard cell One of a pair of specialized cells in the epidermis that regulates the opening and closing of a stoma.
guild In ecology, a group of species that exploit the same class of environment in a similar way.
(Science: botany) guard cells, to go on duty as a guard or sentinel. To run the guard, to pass the watch or sentinel without leave.
Synonym: defense, shield, protection, safeguard, convoy, escort, care, attention, watch, heed.
The plant solution to gas exchange is a new structure, the guard cells that flank openings (stomata) in the above ground parts of the plant. By opening these guard cells the plant is able to allow gas exchange by diffusion through the open stomata.
Each individual pore, or stoma, is, in fact, a small opening between a pair of specialized cells known as guard cells. By modifying the size of the stomata, guard cells are able to regulate gas exchange and transpiration.
The table shows the osmotic pressure measured at different times of day in typical guard cells. The osmotic pressure within the other cells of the lower epidermis remained constant at 150 lb/in2.
Also, water vapor is released into the atmosphere through these pores in a process called transpiration. The opening and closing of a stoma is controlled by guard cells that surround the opening and involves cellular sodium-potassium pumps.
 See also: Cells, Plant, Trans, Stoma, Cell
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