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Structure of plants
· Leaves
· Carbon dioxide diffuses into the air spaces within the leaf.
It then diffuses into the cells for photosynthesis. ( 6CO2 +
6H2O -> C6H12O6 + 6O2)
· The underneath of the leaf is an exchange surface
· Its covered with little holes called stomata which the
carbon dioxide diffuses through
· Water vapour and oxygen diffuse out of the stomata
· The size of the stomata is controlled by guard cells. These
close if the plant is losing too much water.
· The flattened shape of the leaf increases the exchange area…read more

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Structure of plants
· The area inside the leaf forms another exchange
surface which increases the area of the surface so
more carbon dioxide can get into the cells
· The water vapour escapes from the stomata by
transpiration which is where the water vapour
escapes by diffusion because there is a lot more in
the plant than in the air outside. Therefore,
transpiration is faster in hot, dry windy conditions
· A photometer is used to measure the rate of
transpiration from a plant.…read more

Slide 4

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Structure of plants
· The top of the leaf is covered by a waxy cuticle
to prevent transpiration
· The palisade mesophyll and spongy mesophyll
have lots of chloroplasts for photosynthesis
· The outer cells of the leaf are called the upper
and lower epidermis…read more

Slide 5

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Stomata conditions
Condition Stomata Explanation
Loosing heat too quickly Narrower To reduce heat loss
Night Narrower Preserve water when carbon dioxide
isn't needed for photosynthesis
Day Open Allow carbon dioxide in for
photosynthesis…read more

Slide 6

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Other parts
· The stem supports the plant and leaves and it
lifts up the leaves towards light
· The stem also contains the phloem and xylem
· The phloem transports sugars away from the
leaf to other areas for respiration
· The xylem supplies water and mineral ions
from the roots to the leaves and other areas…read more

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