What are the pores present in the epidermis of leaves and stems responsible for gaseous exchange known as?

The pores present in the epidermis of leaves and stems that control gaseous exchange are known as stomata.

Stomata are tiny openings or pores that are surrounded by two specialized cells called guard cells. Stomata play an important role in the process of photosynthesis by regulating the exchange of gases, such as carbon dioxide and oxygen. They also help in the release of excess water vapour from the plant through a process called transpiration. The size of the stomata can be regulated by the opening and closing of the guard cells to control the rate of gas exchange and water loss.