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Adaptations of the leaf to photosynthesis

• The leaf has a flat snd broad lamina to increase surface area for trapping sunlight energy and for gaseous exchange.
• The leaf has numerous stomata through which photosynthetic gases diffuse.
• The leaf is thinto reduce the distance through which carbon (IV) oxide has to diffuse to the photosynthetic cells.
• The palisade mesophyll cells contain numerous chloroplasts which contain chlorophyll molecules which trap sunlight energy for photosynthesis.
• The photosynthetic mesophyll is located towards the upper surface for maximum absorption of sunlight energy.
• The leaf has an extensive network of veins composed of xylem which conducts water to the photosynthetic cells and phloem to translocate manufactured food materials to other plant parts.
• The epidermis and cuticle are transparent to allow light to penetrate to the photosynthetc cells.

Functions of the epidermis:

1. It protects the leaf from mechanical damage.
2. It also protects the leaf from entry of disease-causing microorganisms.
3. It secretes the cuticle.

• There are many small pores on the epidermis known as stomata (singular-stoma) through which exchange of materials occur. The opening and closing of the stomata is controlled by the guard cells. Each stoma is controlled by two guard cells.
• The guard cells have chloroplasts and are bean shaped. They have thicker inner cell wall and thinner outer cell wall.

Adaptations of the guard cells

• They have differentially thicker walls to enable them bulge as they draw water through osmosis from the neighboring cells making them to open the stomata.
• They contain chloroplasts that manufacture sugars which increase osmotic pressure of the guard cells. As they draw water through osmosis, they bulge making the stomata to open.