Covered with a surface of fine pores, such as breathing pores.

Water is continually being pumped upward through the plant in the xylem. Once it reaches the leaves, it is transpired through pores called stomata. Stomata also allow for the passage of carbon dioxide and oxygen in and out (respectively) of the plant. The exchange of air and transpiration of water are regulated by the two cells (called guard cells) on either side of a stomate. There are thousands of stomata on each square centimeter of a typical plant.

a minute epidermal pore in a leaf or stem through which gases and water vapor can pass

A stoma.