Stomata

For leaves to release and take in gases (carbon dioxide, oxygen) and water vapor, the leaf surface has tiny openings called STOMATA (stow-MAH-tah). The plant can regulate the size of stomata by water pressure in the GUARD CELLS that surround the stomata. When the guard cells fill with fluid (become turgid), the stomata open, allowing moisture to escape. The stomata close as the guard cells lose fluid (become flaccid), conserving moisture within the leaf.

Surface of Chrysanthemum leaf showing stoma