Gilliland, Laura Ullrich Department of Biology, Pennsylvania State University, University Park, Pennsylvania.
Assmann, Sarah M. Department of Biology, Pennsylvania State University, University Park, Pennsylvania.
Last reviewed:July 2021
- Mechanism of guard cell volume change
- Environmental response and signaling
- Importance of guard cell investigations
- Related Primary Literature
- Additional Reading
A morphologically distinct cell that is found in the epidermis of terrestrial plant shoots and that functions in regulating stoma size. Guard cells are paired, crescent-shaped epidermal cells that regulate water loss and gas exchange in terrestrial plants. Each pair of specialized guard cells circumscribes and defines a microscopic hole called a stoma (the plural form is stomata) [Fig. 1]. It is through these microscopic pores that plants lose water vapor to the atmosphere, and it is also through these microscopic pores that plants take up carbon dioxide (CO2) gas, which is then fixed into carbohydrate compounds by the internal, photosynthetic cells of the leaf (the mesophyll cells). This exchange of gases with the atmosphere is limited to the stomata because the rest of the epidermis (the outermost cell layer) is covered with a waxy layer—the cuticle (Fig. 1)—that is essentially impervious to these gases. See also: Epidermis (plant); Plant anatomy; Plant cell; Plant organs; Plant tissue system
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