Which plant tissue is primarily responsible for photosynthesis in leaves?

• A. Guard cells
• B. Phloem
• C. Mesophyll cells containing chloroplasts (palisade and spongy)
• D. Xylem

Answer: (C)

Photosynthesis happens mainly in the leaf’s mesophyll tissue, where chloroplasts are abundant. The palisade mesophyll just under the upper surface is packed with chloroplasts, making it the primary light-capture layer. The spongy mesophyll beneath it has air spaces that help gases move around and still contains chloroplasts for continued photosynthesis. Guard cells regulate stomata for gas exchange, but they’re part of the epidermis, not the main photosynthetic tissue. Xylem and phloem transport water and sugars, respectively, and don’t perform photosynthesis. So the tissue best suited for this process is the mesophyll tissue containing chloroplasts (palisade and spongy).