Photosynthesis and Gas Exchange in Plant Leaf Cells

Steps:

• Identify cells in the leaf structure: palisade mesophyll (1) for primary photosynthesis, spongy mesophyll (2) for both photosynthesis and gas diffusion.
• Recall photosynthesis requires chloroplasts in mesophyll cells for light reactions and CO2 uptake.
• Gas exchange involves CO2/O2 diffusion through air spaces in spongy mesophyll and stomata.
• Match numbers: cells 1 and 2 enable both processes via chloroplasts and intercellular spaces.

Why A is correct:

• Palisade (1) and spongy (2) mesophyll cells contain chloroplasts for photosynthesis and facilitate gas exchange through moist surfaces and air spaces, per plant physiology definitions.

Why the others are wrong:

• B: Cell 4 (epidermis) lacks chloroplasts, so no photosynthesis.
• C: Cell 3 (vascular tissue) conducts water/nutrients but performs neither process.
• D: Cells 3 and 4 support transport and protection, not active photosynthesis or gas exchange.

Final answer: A