Describe how the structure of a leaf is adapted to allow efficient photosynthesis. Include in your answer the roles of the palisade mesophyll, spongy mesophyll, and upper epidermis.

The leaf is adapted for efficient photosynthesis by arranging its tissues to maximise light capture and gas exchange.
1. The upper epidermis is thin and transparent, allowing light to reach the photosynthetic cells below.
2. Beneath it lies the palisade mesophyll, a layer of tightly packed, column‑shaped cells positioned close to the upper surface where light intensity is greatest. These cells contain many chloroplasts, so they absorb the maximum amount of light energy.
3. The spongy mesophyll, located below the palisade layer, has loosely arranged cells with large intercellular air spaces. These spaces increase surface area and facilitate rapid diffusion of CO₂ into the cells and O₂ out of the leaf.
Together, this structure ensures that light is efficiently absorbed and gases are rapidly exchanged, enabling optimal photosynthetic rates.