Leaf structure

The leaf is the organ which plants use to make food by photosynthesis. You need to know about the following important parts of a leaf:

The epidermis protects the leaf and is transparent to let light through.

Palisade mesophyll cells are tall and closely packed to absorb maximum light. They contain many chloroplasts. Most photosynthesis takes place in the palisade cells.

Spongy mesophyll also captures light and makes food. Spongy mesophyll cells have air spaces between them to allow easy gas exchange.

Veins contain xylem (top part of vein) for water transport and phloem (lower part of vein) to take away dissolved food.

Stomata (mostly on the underside of the leaf) allow gas exchange; since a lot of water vapour can be lost through the stomata they only open for photosynthesis in daylight; at night they close to reduce loss of water vapour.