Stomata, formed by a pair of kidney-shaped guard cells, are tiny pores in leaves. They act like mouths that plants use to ‘eat’ and ‘breathe.’ When they open, carbon dioxide (CO2) enters the plant for photosynthesis and oxygen (O2) is released into the atmosphere. At the same time as gases pass in and out, a great deal of water also evaporates through the same pores by way of transpiration.
Click here for original story, Structural study gives insight into how plants keep their ‘mouths’ shut
Source: Phys.org