Sunday, 13 March 2016

2.20 describe the structure of the leaf and explain how it is adapted for photosynthesis


This is the inside of a leaf

Shows the waxy cuticle on top of the upper epidermis.Under this is the palisade mesophyll layer and spongy mesophyll layer, which has air spaces in it. At the bottom, is the lower epidermis and wax cuticle. Gases are exchanged through the stoma. On each side of the stoma there is a guard cell with chloroplasts.
Adaptations (external/structural)
A large surface area - to absorb maximum light
Thin - short distance for carbon dioxide to diffuse into leaf cells
Network of veins - allows the transport of water (and carbohydrates) - veins also support the leaf, although this does not affect photosynthesis
Stomata - allows carbon dioxide to diffuse into the leaf (and oxygen, the bi-product of photosynthesis, to leave the leaf

Adaptations (internal)
Wax cuticle - Protects the leaf without blocking light
Upper Epidermis - is thin and transparent (clear) to allow more light to reach the palisade cells
Palisade mesophyll - filled with chloroplasts (which contain chlorophyll) to absorb all the available light
Spongy mesophyll/air spaces - allow carbon dioxide to diffuse through the leaf, and increase the surface area
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