THIS IS EXTRA INFORMATION FOR THOSE STUDENTS INTERESTED IN THE STRUCTURES PLANTS HAVE THAT ALLOW THEM TO FUNCTION. YOU WILL NOT BE TESTED ON THIS INFORMATION. |
Credit: Mariana Ruiz Villarreal (LadyofHats) for CK-12 Foundation
Source: CK-12 Foundation License: CC BY-NC 3.0 |
Credit: LadyoHats for CK-12
Source: http://commons.wikimedia.org/wiki/File:Leaf_anatomy_universal.svg License: CC-BY-NC-SA 3.0 |
The openings or pores in stomata are formed by two specialized guard cells. In daylight or high humidity, when CO2 is needed for photosynthesis and water loss can be minimized, the guard cells expand to open the pores. Closing the stomata is controlled by signals from roots when they sense water shortage.
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An microphotograph (figure to the left) of a stoma shows the two guard cells which regulate its opening and closure to limit water loss, excrete oxygen, and absorb carbon dioxide.
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