structure of a plant · structure of a plant • roots • stems • flowers • leaves • each...
TRANSCRIPT
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Plant Structure Plant Structure Plant Structure Plant Structure & Function& Function& Function& FunctionStructure of a Plant
• Roots
• Stems
• Flowers
• Leaves
• Each has its own specialised structure &
function within the plant
Roots
• Anchor plants in the soil
• Hold soil in place and prevent erosion
• Absorb water & nutrients (oxygen, minerals) for the plant:– Oxygen, carbon dioxide
– Nitrogen
– Phosphorus
– Potassium
– Magnesium
– Calcium
Root Hairs
• Small hairs on roots
• Increase the surface area available
to absorb water & nutrients
Stems
• Provide support for the plant –holds up leaves and flowers
• Carries nutrients throughout the plant
• Two specific transport structures contained in the stem: xylem and phloem
Xylem
• Tubes with strong, thick walls that assist with supporting the plant
• Transport water from roots to flowers/leaves – called a transpiration stream
• Water vapour evaporates through openings in the leaves called stomata -process called transpiration
• This creates a suction that pulls the water up through the xylem from the roots
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Phloem
• Organic substances
such as sugars are
transported
throughout the
plants
• Process is called
translocation
Transpiration vs Translocation Leaves
• Trap sunlight so plants
can perform
photosynthesis
• Allow plant to take in
carbon dioxide and
release oxygen
Photosynthesis
• Photosynthesis: the process through which plants covert energy from sunlight into glucose
• Photosynthesis occurs in chloroplasts that are found in leaf cells
• Chloroplasts contain chlorophyll
• Chlorophyll absorbs light energy
Photosynthesis
• Carbon dioxide enters leaves from
atmosphere
• Water that has travelled from roots
• Glucose will be used by the plant
for energy
• Oxygen released from leaves into
atmosphere
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Leaf Structure Stomata
• Small pores in the surface of leaves (usually on the underside)
• Allows the exchange of oxygen and carbon dioxide
• Stomata are surrounded by
guard cells on either side
• Stomata can open and close
to allow more/less water,
oxygen & carbon dioxide
in/out
How do stomata open & close?
• When plant has plenty of water, water
moves into the guard cells, making
them turgid
• This opens the stoma
• If the plant does not have enough
water, guard cells lose water and
become flaccid
• This closes the stoma as the guard
cells collapse towards each other
Why do stomata open & close?
• When stomata are open, the plant loses water by
evaporation
• Stomata will close to prevent too much water loss
• Cannot remain closed as stomata allow exchange of
oxygen and carbon dioxide
Flowers
• Reproductive structure of a plant
Male & Female Reproductive Organs
MALE
• Stamen: anther & filament
• Anther contains pollen, which will fertilise the
egg
FEMALE
• Pistil: stigma, style & ovary
• Ovaries produce eggs (female reproductive cell)
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Type of Pollination
• For an egg to be fertilised, pollen must be
transferred from the anther to the stigma
Self Pollination
A flower is pollinated with its own
pollen or pollen or the pollen of a
flower on the same plant
Cross Pollination
A flower is pollinated by a flower of the
same species from a different plant
Method of Pollination
Wind Pollination
• Pollen is transferred via wind
• Usually have a feathery stigma to catch the pollen
Animal Pollination
• Pollen transferred via animals such as insects or birds
• Flowers usually brightly coloured to attract the
animals
• Animals may be rewarded with nectar