Structure of a Leaf (WJEC GCSE Biology): Revision Note
Structure of a Leaf
Leaves are plant organs; they are adapted to maximise the rate of photosynthesis
Leaf structure diagram
Leaf structure is adapted to maximise photosynthesis
Leaf structures & functions table
Structure | Function |
|---|---|
Cuticle | A waxy layer that reduces evaporation from leaf surfaces |
Epidermis | A thin layer of cells that are transparent to allow light to reach photosynthesising cells |
Palisade mesophyll layer | A layer of palisade cells at the top of the leaf that contains many chloroplasts; these features maximise light absorption |
Spongy layer | Air spaces between cells allow the movement of gases |
Xylem | Transports water from the roots to the leaves |
Phloem | Transports the products of photosynthesis to the rest of the plant |
Stomata | Allow gases to move in and out of the leaf |
Guard cells | Can close to prevent excessive water loss in dry conditions |
Stomata
Stomata (singular stoma) are pores on the underside of leaves that allow gas exchange
Photosynthesising cells need carbon dioxide for photosynthesis
Oxygen is released from photosynthesising leaves as a waste product
Stomata also allow water vapour to diffuse out of leaves, maintaining the upward movement of water in the xylem
Guard cells surround the stomata; when water availability is low the guard cells can cause the stomata to close, preventing loss of water vapour by transpiration
Stomata diagram
Stomata can close to reduce water loss by transpiration
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