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Plants at work
J E F Frost
Plants at work
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Plants are producers
Plants get their energy from light
Plants make food by photosynthesis
Light energy is trapped by chlorophyll
Most of the food is stored as starch
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Photosynthesis
Word equation
sunlight
Carbon dioxide + water
chlorophyll
sugar + oxygen
Plants make new biomass during photosynthesis
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Leaves
Leaves are green because they contain
chlorophyll
Leaves have a large surface area to absorb as
much light as possible
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Testing for starch
Iodine changes from brown to blue-black
where there is starch
Method
Soften the leaf with boiling water
Remove the green colour with ethanol
Add drops of iodine
Look for the colour change!
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Variegated leaves
Some leaves are not green all over
Some have white and green stripes or patches
Only the green parts will contain starch
Why?
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Respiration in plants
All living things carry out respiration
Leaves are thin so that gases can get in and out
easily
Gases get into and out of leaves through little
holes called stomata
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Section through a leaf
Waxy layer
Palisade cells
Spongy cells
Air space
Stomata
Guard cell
Lower surface
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Plant growth
•Plants need carbon dioxide from the air
•Plants need water
•Plants need light
•Plants need nutrients from the soil including
nitrogen, phosphorus and potassium
•If the soil does not contain enough nutrients
then we add fertilisers
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Fertilisers
Nitrogen is needed for general growth
Phosphorus is needed for healthy roots
Potassium is needed for healthy leaves
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Plant plumbing
Water and minerals enter the plant through
the roots
Then they go up through little tubes called
xylem in the plant stem
Food is transported through tiny tubes in the
stem called phloem
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Roots
Roots keep the plant anchored in the soil
Roots are covered in lots of tiny hairs
Root hairs take up water from the soil
All the root hairs together have a large
surface area
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Flowers
Flowers are a plant’s reproductive system
Flowers have male and female reproductive
organs
Male part (stamen): anther and filament
Female part (carpel): stigma, style, ovary
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Pollination
Pollination is the transfer of pollen (male) to the
stigma (female)
Pollen grains can be carried by insects
Pollen grains can be carried by the wind
When the ovule is fertilised it turns into a seed
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Making seeds
stigma
Pollen grain
style
ovule
ovary
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ovule
nucleus
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Key words
plant
seed
root
stem
leaf
root hair
starch
J E F Frost
chlorophyll
photosynthesis
carbon dioxide
oxygen
phosphorus
nitrogen
potassium
Plants at work
pollen
anther
filament
stigma
style
ovule
xylem
phloem
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