Openings in the outer cell layer of leaves that enable the exchange of gases.

Tiny openings called stomata which is responsible for the exchange of gases between leaves and environment.

Explanation:

Stomata are present on the epidermis of the leaf. Stomata opening and closing is controlled by guard cells. When photosynthesis process starts, stomata opens and allow carbondioxide into the leaves while when photosynthesis over and oxygen is produced. Again stomata opens and release the oxygen to the atmosphere.

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