Guard cells are specialized plant cells in the epidermis of leaves, stems and other organs that are used to control gas exchange. They are produced in pairs with a gap between them that forms a stomatal pore. The stomatal pores are largest when water is freely available and the guard cells become turgid, and closed when water availability is critically low and the guard cells become flaccid. Photosynthesis depends on the diffusion of carbon dioxide (CO2) from the air through the stomata into the mesophyll tissues. Oxygen (O2), produced as a byproduct of photosynthesis, exits the plant via the stomata. When the stomata are open, water is lost by evaporation and must be replaced via the transpiration stream, with water taken up by the roots. Plants must balance the amount of CO2 absorbed from the air with the water loss through the stomatal pores, and this is achieved by both active and passive control of guard cell turgor pressure and stomatal pore size.[1][2][3][4]
- ^ Schroeder JI, Kwak JM, & Allen GJ (2001) Guard cell abscisic acid signaling and engineering drought hardiness in plants. Nature 410:327-330.
- ^ Hetherington AM & Woodward FI (2003) The role of stomata in sensing and driving environmental change. Nature 424:901-908.
- ^ Shimazaki K, Doi M, Assmann SM, & Kinoshita T (2007) Light regulation of stomatal movement. Annu Rev Plant Biol 58:219-247.
- ^ Kwak JM, Mäser P, & Schroeder JI (2008) The clickable guard cell, version II: Interactive model of guard cell signal transduction mechanisms and pathway. The Arabidopsis Book, eds Last R, Chang C, Graham I, Leyser O, McClung R, & Weinig C (American Society of Plant Biologists, Rockville), pp 1-17.