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Feeding in plants



Photosynthesis:

Carbon dioxide + water glucose + oxygen
6CO2 6H20 C6H1206 602




Chlorophyll absorbs light
Light energy converts carbon dioxide and water into glucose
Before testing for photosynthesis, you must de-starch the plant by
leaving it in the dark for 24 hours.




Dissolved food is carried around…

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Rate of photosynthesis

Scientists try to increase the rate of photosynthesis to increase the yield of a
crop.

LIMITING FACTORS

Light
more light, faster photosynthesis
plants spread their leaves to catch as much light as possible
too strong light can damage chloroplasts



Carbon Dioxide
The more CO2 a plant has,…

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Structure of a leaf




WAXY CUTICLE: waterproof layer. Cuts down water lost by evaporation
UPPER EPIDERMIS: single layer of cells with no chloroplasts. Light goes
straight through.
PALISADE LAYER: Contains lots of chloroplasts. Most photosynthesis
occurs here.
SPONGY LAYER: rounded cells with space between for gas exchange
VEIN: contain xylem…

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Stomata

Small holes on the underside layer of the leaf that allows gases to diffuse in
and out.
Stomata can be opened and closed by guard cells
Open during the day, closed during the night
Water passes into the guard cells by osmosis
Close in hot weather to prevent water…

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Plant Nutrients

Plants need mineral salts and nutrients for growth found in the soil and
taken up by roots by active transport
The 3 main minerals need are:




When soil does not contain enough nutrients, fertilisers are added to replace
the missing ones.
The proportions of nitrogen, phosphorus and potassium…

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Phosphate Phosphate is needed for Poor root growth and
healthy roots purple leaves
Potassium Needed for healthy Yellow leaves with dead
leaves and flowers spots
Magnesium Magnesium is needed Yellow leaves
for chlorophyll



Natural and Chemical Fertilisers

Easy to store and add to the land (+)
Rain can wash fertilisers…

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Carbon Dioxide
o Growers can pump carbon dioxide into the glass houses to increase
photosynthesis
o Paraffin heaters release CO2




Water
o Automatic watering systems are used
o Sprinklers and humidifiers turn on when needed




(All these factors are controlled by computer. Sensors are used to detect each
factor.)

Growth…

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The Roots




Into the roots

Root hairs = long, thin, large surface area
Anchor the plants into the soil
Water passes into root hairs by osmosis ­ water in soil has high water
concentration and cell sap in root hairs has lower water concentration




The Stem

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Cambi
um
Cel
ls Make new xylem and
phloem as the cell
grows

Epi
der
mis Single layer of cells
on the outside of the
stem which protects
the stem and cuts
down water loss

Vasc
u l
ar Contain phloem,

bundl
es cambium and xylem




Transpiration

When water evaporates…

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