Which plant structure is primarily responsible for gas exchange with the atmosphere?

Which plant structure is primarily responsible for gas exchange with the atmosphere?

• A. Xylem
• B. Phloem
• C. Stomata
• D. Cortex

Answer: (C)

Gas exchange with the atmosphere occurs mainly through stomata, tiny pores on the surface of leaves that are usually found on the underside. Each pore is bordered by a pair of guard cells that control its opening and closing. When stomata are open, carbon dioxide from the air can diffuse into the leaf for photosynthesis, and oxygen produced inside can diffuse out. Water vapor can also exit during transpiration, which is why stomatal opening is tightly linked to the plant’s water status. Other vascular tissues have different roles and don’t primarily mediate gas exchange. Xylem transports water and minerals from roots to shoots, while phloem distributes sugars and other organic nutrients; cortex is a tissue layer involved in support and storage in stems and roots, not in exchanging gases with the atmosphere. While some other parts like lenticels can allow gas exchange in some stems, stomata are the main structures responsible for gas exchange in most terrestrial plants.

Gas exchange with the atmosphere occurs mainly through stomata, tiny pores on the surface of leaves that are usually found on the underside. Each pore is bordered by a pair of guard cells that control its opening and closing. When stomata are open, carbon dioxide from the air can diffuse into the leaf for photosynthesis, and oxygen produced inside can diffuse out. Water vapor can also exit during transpiration, which is why stomatal opening is tightly linked to the plant’s water status.

Other vascular tissues have different roles and don’t primarily mediate gas exchange. Xylem transports water and minerals from roots to shoots, while phloem distributes sugars and other organic nutrients; cortex is a tissue layer involved in support and storage in stems and roots, not in exchanging gases with the atmosphere. While some other parts like lenticels can allow gas exchange in some stems, stomata are the main structures responsible for gas exchange in most terrestrial plants.