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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