Leaf Structure

Leaf Structure

Upper Epidermis

• The upper epidermis is a layer of cells that protects the leaf.
• It is transparent, allowing light to pass through to the chloroplasts in the cells below.
• Above this layer, there’s a thin layer of wax called the cuticle which helps to reduce water loss.

Palisade Mesophyll

• Below the upper epidermis is the palisade mesophyll, packed with long, column-shaped cells.
• These cells contain large amounts of chloroplasts for maximum photosynthesis.
• Being situated just beneath the upper epidermis, they can capture plenty of light.

Spongy Mesophyll

• Underneath the palisade mesophyll is the spongy mesophyll, a layer of irregularly-shaped cells with air gaps in between.
• These air gaps allow gases like carbon dioxide and oxygen to reach the cells easily.
• Spongy cells are also equipped with few chloroplasts for photosynthesis.
• The moist surfaces of the spongy mesophyll cells allow for gas exchange between the cell and the air spaces.

Lower Epidermis

• The lower epidermis is located on the underside of the leaf.
• It is studded with structures called stomata (singular: stoma), surrounded by two guard cells.
• Stomata allow gases to move in and out of the leaf, particularly carbon dioxide, oxygen and water vapour.
• Guard cells control the opening and closing of the stomata, regulating gas exchange and water loss.

Vein

• The vein contains the xylem and phloem which transport water, minerals and sugars to and from the leaf.
• Xylem vessels carry water and dissolved minerals from roots to leaves.
• Phloem vessels transport dissolved sugars from leaves (where they’re made during photosynthesis) to other parts of the plant.

Remember, all these parts work together to optimise photosynthesis - the process in which the plant makes its own food.