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# Carbon Dioxide Uptake ## Structure in Leaves The structures in leaves that show the pathway for gas exchange are as depicted in Figure 2.18. Carbon dioxide absorption occurs through stomata allowing for a difference in concentration between the inside of the cells and the air spaces. ## Carbon...

# Carbon Dioxide Uptake ## Structure in Leaves The structures in leaves that show the pathway for gas exchange are as depicted in Figure 2.18. Carbon dioxide absorption occurs through stomata allowing for a difference in concentration between the inside of the cells and the air spaces. ## Carbon Dioxide Uptake in Photosynthesis 1. When carbon dioxide is used in the process of photosynthesis, the concentration of carbon dioxide in the cell becomes lower than that of the surrounding air spaces. This difference in concentration allows carbon dioxide to move from the air space into the cell. The dissolved carbon dioxide on the moist cell surface will then diffuse into the cell. ## Diffusion of Carbon Dioxide 2. This causes the carbon dioxide concentration in the air spaces to decrease compared to the concentration outside. This difference in concentration encourages carbon dioxide absorption from the atmosphere across the open stomata. **Diagram Labels** The diagram shows a cross-section of a leaf and labels indicating the areas and processes involved in carbon dioxide absorption. * **Cuticle:** Outer waxy layer * **Upper epidermis:** Top layer of cells * **Intercellular air spaces:** Spaces between cells * **Lower epidermis:** Bottom layer of cells * **Guard cells:** Cells surrounding stomata * **Stoma:** Opening in the leaf for gas exchange * **Air space/ Intercellular spaces/ Intercellular air spaces:** Air pockets inside the leaf * **Mesophyll cells:** Cells containing chloroplasts * **Palliade mesophyll cells:** Cells packed tightly together in layers. * **Spongy mesophyll cells:** Loosely arranged cells. * **Xylem:** Transports water and minerals * **Phloem:** Transports sugars during photosynthesis * **Guard cells:** Regulate the size of the stomata * **Stomata:** Pore-like openings on the leaf surface **Legend** * Red arrow : Carbon dioxide (CO₂) * Blue arrow : Oxygen (O₂)