Through which tiny openings in the leaf does gas exchange primarily occur?

Through which tiny openings in the leaf does gas exchange primarily occur?

• A. Stomata
• B. Guard cells
• C. Xylem
• D. Phloem

Answer: (A)

Gas exchange in leaves occurs mainly through stomata, the tiny pores in the leaf epidermis. These openings, surrounded by guard cells, can open or close to regulate gas flow. When stomata are open, carbon dioxide from the air can diffuse into the leaf for photosynthesis, while oxygen produced and water vapor exit. The guard cells respond to light, internal CO2, and water status to balance CO2 intake with water loss. Xylem and phloem are vascular tissues that transport water, minerals, and sugars, not the pores for gas exchange, so they don’t serve this function.

Gas exchange in leaves occurs mainly through stomata, the tiny pores in the leaf epidermis. These openings, surrounded by guard cells, can open or close to regulate gas flow. When stomata are open, carbon dioxide from the air can diffuse into the leaf for photosynthesis, while oxygen produced and water vapor exit. The guard cells respond to light, internal CO2, and water status to balance CO2 intake with water loss. Xylem and phloem are vascular tissues that transport water, minerals, and sugars, not the pores for gas exchange, so they don’t serve this function.