Think about it

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Think about it 9.1 What do organisms need for
life? 9.2 How do plants achieve
nutrition? 9.3 How do plants exchange gases with
the environment? Practical 9.1 Practical
9.2 Practical 9.3 STS connection 9.1 Summary
concept diagram
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Little Susan thought that this is how plants
obtain their food
What is the plant in the cartoon doing? Why?
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Little Susan thought that this is how plants
obtain their food
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Little Susan thought that this is how plants
obtain their food
How is the plant in the cartoon different from a
plant in reality?
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Little Susan thought that this is how plants
obtain their food
A car needs fuel to function. Similar to a car,
plants have their basic needs to maintain life.
They have special ways to obtain these needs.
How is the plant in the cartoon different from a
plant in reality?
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Our Hydroponic Greenhouse   
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9.1 What do organisms need for life?
Two important processes involved
Nutrition (????)
Gas exchange (????)
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9.1 What do organisms need for life?
1 Nutrition
? Obtain the food substances to maintain life.
? e.g. proteins (???), fats (??) and
carbohydrates (?????)
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9.1 What do organisms need for life?
2 Gas exchange
? obtain oxygen for aerobic respiration
? obtain carbon dioxide for photosynthesis in
plants and algae
? release gases produced from these two processes
to the environment
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9.2 How do plants achieve nutrition?
Plants produce carbohydrates (food) during
photosynthesis on their own.
food
? known as autotrophs (????)
? Their mode of nutrition (????) is called
autotrophic nutrition (????).
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9.2 How do plants achieve nutrition?
Plants also absorb minerals and water from the
soil through the roots.
Using these nutrients, plants can make everything
they need and maintain life.
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carbon dioxide and water
photosynthesis
mineral salts from soil (e.g. NO3-, SO42-)
carbohydrates (e.g. glucose)
amino acids
join together to become protein molecules
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9.2 How do plants achieve nutrition?
Minerals essential for plant growth
Two types of minerals
1) Major elements (????)
? required in large amount, e.g. nitrogen, ,
magnesium, phosphorous, sulphur and calcium
2) Trace elements (????)
? required in small amount, e.g. copper, zinc and
boron (?)
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9.2 How do plants achieve nutrition?
Minerals essential for plant growth
If the amount of any of these minerals is
insufficient, plants will suffer from deficiency
diseases.
? small and yellow leaves
? curled-up leaves
? thin stems and poor root formation
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Extension
Minerals essential for plant growth
Nitrogen
? important for the synthesis of proteins
? Proteins are made up of amino acids (???) which
contain nitrogen.

• Deficiency disease
• poor growth and yellowing of leaves

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Extension
Minerals essential for plant growth
Nitrogen
? Nitrogen is mainly absorbed in the form of
nitrate
ammonium salts
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Extension
Minerals essential for plant growth
Magnesium
? important for the synthesis of chlorophyll
? It forms part of the chlorophyll molecule.

• Deficiency disease yellowing of leaves

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. Apple Leaves Nitrogen deficiency - leaf small
and yellow
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Magnesium Deficiency Chlorosis / yellowing of
leaf
Complete Nutrient Solution Healthy growth.
Potato Plant
Nitrogen Deficiency Severely restricted
growth, Yellowing of leaf
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The importance of nitrogen

• For synthesis of proteins, chlorophyll, etc
• Taken in form of nitrate ions
• Deficiency symptoms
• Little growth ( - no protein made)
• Yellowing of leaves ( - no chlorophyll made)

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The importance of magnesium

• Essential component of chlorophyll
• Deficiency symptoms
• Yellowing of leaves (no chlorophyll made)
• Poor growth (no food manufactured because of lack
  of chlorophyll)

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9.1
Investigation of the effects of different
minerals on plant growth
Procedure
1 Label 5 similar pots of seedlings from A to E.
magnesium- deficient E
complete nutrients A
nitrogen- deficient B
phosphorus- deficient C
potassium- deficient D
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9.1
Investigation of the effects of different
minerals on plant growth
Procedure
2 Observe and write down the general appearance
of the seedlings.
magnesium- deficient E
complete nutrients A
nitrogen- deficient B
phosphorus- deficient C
potassium- deficient D
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9.1
Investigation of the effects of different
minerals on plant growth
Procedure
3 Fill the trays with the following nutrient
solutions
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9.1
Investigation of the effects of different
minerals on plant growth
Procedure
4 Put the pots of seedlings in bright light. At
intervals, refill with fresh nutrient solutions.
If algae grow in the trays, clean the trays and
renew with respective fresh nutrient solutions.
5 After 2 to 3 weeks, record the appearance of
the seedlings again.
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Extension
Use of chemical fertilizers in agriculture
Minerals in the soil come from
? dissolution of rocks by rain
? decay of dead organisms
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Natural fertilizers

• From manure
• Organic compounds in it are decomposed by the
  bacteria in soil to form mineral salts

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Chemical fertilizers

• Mainly nitrogenous and phosphorous compounds
  manufactured artificially

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Extension
Use of chemical fertilizers in agriculture
If farmers grow many plants close together,
consumption of minerals gt supply of minerals
? Farmers must supply additional minerals to
the soil
Chemical fertilizers
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Extension
Use of chemical fertilizers in agriculture
Chemical fertilizers are mixtures of the
necessary minerals in the correct proportions.
Proportion depends on
? type of soil,
? type of crops grown
? stages of the crop growth
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Extension
Use of chemical fertilizers in agriculture
Nitrogen (N), phosphorus (P), potassium (K),
calcium, magnesium and sulphur are common
components of chemical fertilizers.
Usually added to the soil in large quantities.
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Extension
Use of chemical fertilizers in agriculture
It means that the fertilizer contains 25
nitrogen (N) 5 phosphorus (P) and
20 potassium (K) by weight.
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9.1
Application of chemical fertilizers and its
environmental consequences
? About a quarter of the coral reefs (???) in the
Great Barrier Reef (???) will be lost due to the
overuse of chemical fertilizers. Try to find out
more examples and suggest alternatives to
chemical fertilizers.
Go to Activity Book 2, p.10
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9.3 How do plants exchange gases with the
environment?
O2 (for respiration)
CO2 (for photosynthesis)
Plants
CO2 (from respiration)
O2 (from photosynthesis)
Plants exchange gases by diffusion through
leaves, stem and roots.
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9.3 How do plants exchange gases with the
environment?
Leaves
Cuticle limits the diffusion of gases
Stoma gases mainly diffuse through it
Guard cells control the opening and closing of
stoma
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Leave
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9.3 How do plants exchange gases with the
environment?
Roots
Roots are not covered by a cuticle. Gas exchange
takes place all over their surfaces.
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Root Hair
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9.3 How do plants exchange gases with the
environment?
Stem
Lenticel gases diffuse through it on the woody
stems
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Stems and Roots Must Exchange CO2 and O2 also
28.8

• Pores in stems called lenticels allow gas
  exchange
• many cells of living stems are dead (providing
  strucural support only)
• Root can be deprived of oxygen in waterlogged
  soils

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Extension
Gas exchange in the daytime and in the dark
Gas exchange in plants is affected by
Respiration
Photosynthesis
uptake
release
release
uptake
takes place only when the light intensity is high
enough
both in the daytime and in the dark
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Extension
The net uptake and release of O2 or CO2 depend on
which process is happening at a faster rate.
Gas exchange in the daytime and in the dark
Gas exchange in plants is affected by
Respiration
Photosynthesis
uptake
release
release
uptake
takes place only when the light intensity is high
enough
both in the daytime and in the dark
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Extension
Gas exchange in the daytime and in the dark
In the daytime
net release of O2
? light intensity is high

• rate of photosynthesis gt
• rate of respiration

net uptake of CO2
a net uptake of carbon dioxide a net release of
oxygen
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Extension
Gas exchange in the daytime and in the dark
In the dark
net release of CO2
? light intensity is very low

• photosynthesis stops and only respiration occurs

uptake of O2
a net uptake of oxygen and a net release of
carbon dioxide from respiration
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Extension
The relationship between gas exchange and light
intensity
Point A

• in the dark, only respiration takes place

• absorb O2,
• release CO2

A
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Extension
The relationship between gas exchange and light
intensity
Point B

• light intensity slowly increases

• photosynthesis takes place

• net release of CO2 is decreased

B

• net uptake of O2 is decreased

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Extension
The relationship between gas exchange and light
intensity
Point C

• rate of photosynthesis rate of respiration

• no net gas exchange occurs

• this is called compensation point (???)

C
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Extension
The relationship between gas exchange and light
intensity
Point D

• light intensity increases further

• rate of photosynthesis gt rate of respiration

• absorb CO2 and release O2

D
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Extension
The relationship between gas exchange and light
intensity
Point E

• light intensity increases even further

• more CO2 is absorbed and more O2 is released

E
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Extension
9.2
Investigation of the effect of light intensity on
gas exchange in plants using red
hydrogencarbonate indicator
Procedure
1 Set up the boiling tubes as shown. Make sure
each tube contains the same amount of red
hydrogencarbonate indicator.
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Extension
9.2
Investigation of the effect of light intensity on
gas exchange in plants using red
hydrogencarbonate indicator
Procedure
2 Leave the set-up undisturbed for 5 hours. Note
any colour changes in the hydrogencarbonate
indicator.
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Extension
9.3
Investigation of the effect of light intensity on
gas exchange in plants using a data logger
Procedure
1 Connect the low pressure sensor, the data
logger interface and the computer.
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Extension
9.3
Investigation of the effect of light intensity on
gas exchange in plants using a data logger
Procedure
2 Set up the apparatus as shown. Switch on the
lamp.
low pressure sensor
to data logger interface
rubber tubing
water
stopper
dilute sodium hydrogen-carbonate solution
bench lamp
Hydrilla
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Extension
9.3
Investigation of the effect of light intensity on
gas exchange in plants using a data logger
Procedure
3 Allow 5 minutes for the plant to equilibrate.
Then disconnect the rubber tubing from the low
pressure sensor to release the pressure
carefully. Re-connect the tubing.
low pressure sensor
to data logger interface
rubber tubing
water
stopper
dilute sodium hydrogen-carbonate solution
bench lamp
Hydrilla
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Extension
9.3
Investigation of the effect of light intensity on
gas exchange in plants using a data logger
Procedure
4 Start recording for 10 minutes. It is the
bright light condition.
low pressure sensor
to data logger interface
rubber tubing
water
stopper
dilute sodium hydrogen-carbonate solution
bench lamp
Hydrilla
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Extension
9.3
Investigation of the effect of light intensity on
gas exchange in plants using a data logger
Procedure
5 Wrap the boiling tube with one layer of muslin.
Repeat 3 and 4. It is the moderate light
condition.
low pressure sensor
to data logger interface
rubber tubing
water
stopper
dilute sodium hydrogen-carbonate solution
bench lamp
Hydrilla
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Extension
9.3
Investigation of the effect of light intensity on
gas exchange in plants using a data logger
Procedure
6 Wrap the boiling tube with two layers of
muslin. Repeat 3 and 4. It is the dim light
condition.
low pressure sensor
to data logger interface
rubber tubing
water
stopper
dilute sodium hydrogen-carbonate solution
bench lamp
Hydrilla
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Extension
9.3
Investigation of the effect of light intensity on
gas exchange in plants using a data logger
Procedure
7 Wrap the boiling tube with aluminium foil.
Repeat 3 and 4. It is the dark condition.
low pressure sensor
to data logger interface
rubber tubing
water
stopper
dilute sodium hydrogen-carbonate solution
bench lamp
Hydrilla
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Extension
9.3
Investigation of the effect of light intensity on
gas exchange in plants using a data logger
Procedure
8 Find out the pressure change for each run of
data from the difference between the minimum and
maximum pressure.
low pressure sensor
to data logger interface
rubber tubing
water
stopper
dilute sodium hydrogen-carbonate solution
bench lamp
Hydrilla
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Summary concept diagram
Plants
obtain and exchange
are
autotrophs
gases
which obtain
through
food substances
roots
lenticels
stomata
by
in
on
stems
leaves
photosynthesis
absorption
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Summary concept diagram
absorption
of
can be artificially made into
water
minerals
such as
E
E
E
chemical fertilizers
magnesium
nitrogen
Back to summary concept diagram