Where does the primary photosynthesis take place in leaves?

Photosynthesis primarily takes place in the palisade mesophyll of leaves due to its structure and role. The palisade mesophyll consists of tightly packed cells that are rich in chloroplasts, which contain chlorophyll necessary for capturing light energy. This arrangement maximizes light absorption, as the cells are oriented vertically beneath the upper epidermis of the leaf, allowing them to efficiently capture sunlight.

While the spongy mesophyll also contains chloroplasts and contributes to photosynthesis, it primarily facilitates gas exchange and contains air spaces that allow for the diffusion of carbon dioxide. The cuticle serves as a protective barrier that reduces water loss and does not play a direct role in photosynthesis. Guard cells regulate the opening and closing of stomata to control gas exchange, but they do not conduct photosynthesis themselves.

Therefore, the palisade mesophyll is specifically adapted for the primary function of photosynthesis, making it the correct answer to the question.