Plant Pre-learning notes.ppt

© Boardworks Ltd 2004
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KS4 Biology
Plant Nutrition

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The rate of photosynthesis
Minerals from the soil
Plant Nutrition
What is photosynthesis?
More about photosynthesis
Contents
How do plants make food?
Multiple-choice quiz

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All living organisms
need food to grow
and survive.
How do plants get the food they need?
Plants are known as
producers because
they provide food for
many other organisms.
Plants cannot move
very much, so how
do they get the food
that they need?

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Green plants are amazing
because they actually
make their own food!
Green plants are the
only living organisms
that are able to do this.
All other organisms rely
on plants because of the
food that the plants make.
What is the name of the
process by which plants
make their own food?
Nutrition in green plants

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Plants make their own food by photosynthesis.
This process is a chemical reaction that uses light energy.
light energy
The word photosynthesis comes
from the Greek language:
“photo” means “light”
“synthesis” means “putting together”
Photosynthesis just means “putting together with light”.
What do green plants “put together” to make their food?

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Plant Nutrition
Contents

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The raw materials
for photosynthesis
come from the air
and the soil.
What are these raw
materials called?
What else do plants
need to turn
carbon dioxide
and water into food?
Photosynthesis: raw materials
carbon
dioxide
water

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Photosynthesis is a
chemical reaction
between carbon
dioxide and water.
Energy is needed
for this reaction to
take place.
Where do plants
get this energy
from?
Photosynthesis: energy for the reaction
carbon
dioxide
water
light
energy

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Plants use light
energy from the
Sun to power
photosynthesis.
Where in the leaf
does this reaction
take place?
Photosynthesis
takes place in what
part of plant cells?
Photosynthesis: where it happens
carbon
dioxide
water
light
energy

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Photosynthesis takes
place in plant cells
with chloroplasts.
Chloroplasts contain
the green chemical
called chlorophyll.
Chlorophyll absorbs
the energy from
sunlight that allows
carbon dioxide and
water to react.
What are the products
of this reaction?
Photosynthesis: where it happens
carbon
dioxide
water
light
energy
chlorophyll

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The products of the
reaction between
carbon dioxide and
water are glucose
and oxygen.
Which of these
products is used
by plants?
What happens to the
‘waste’ product?
Photosynthesis: products of the reaction
carbon
dioxide
water
glucose
oxygen
light
energy
chlorophyll

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Glucose is the useful
product for plants.
Some glucose is used
straightaway by plant
cells, some is
converted to starch
for storage and later
used for food.
Oxygen is the ‘waste’
product. This gas is
transported out of the
leaf into the air.
Why is this important
for humans and other
living things?
Photosynthesis: products of the reaction
carbon
dioxide
water
oxygen
light
energy
chlorophyll
glucose
oxygen
glucose

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Photosynthesis: summary
Summarize the process of photosynthesis in one sentence.
Photosynthesis is a chemical reaction which means it can
also be summarized in a word equation.
What is the word equation for this vital chemical reaction?
Photosynthesis is a chemical reaction
that takes place in the chloroplasts
in green plant cells, where light energy
is used to convert carbon dioxide and water
into glucose and oxygen.

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Photosynthesis: word equation
carbon
dioxide
water
oxygen
light
energy
chlorophyll
glucose
glucose
light energy
chlorophyll
carbon
dioxide water oxygen

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Photosynthesis: word equation activity

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Photosynthesis: chemical formulae?
Photosynthesis is a chemical reaction involving molecules.
glucose
light energy
chlorophyll
carbon
CO2 H2O O2
C6H12O6
The chemical formula of a glucose molecule is C6H12O6.
What are the chemical formulae of the simple molecules
that make up carbon dioxide, water and oxygen?

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Word equation to chemical equation

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Photosynthesis multiple-choice quiz

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Plant Nutrition
Contents

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Leaves: maximizing photosynthesis
Leaves are the most efficient
solar panels on Earth!
Why can they be called this?
Light energy is absorbed
by the chlorophyll in leaves
and used to carry out
photosynthesis.
Leaves come in all shapes
and sizes but what features
do they have in common
to maximize photosynthesis?

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Structure of a leaf
How are leaves designed to maximize photosynthesis?
Leaves are wide and flat
to create a large surface
area and to absorb
as much light as possible.
Leaves are thin so gases
can reach cells easily.
Leaves have holes, called
stomata, on their
underside through which
gases move in and out.
Leaves have lots of veins
to carry water to the cells
and carry glucose away.

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Structure of a leaf activity

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Take a look inside a leaf

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What happens to the glucose?

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Testing leaves for starch – procedure

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Testing leaves for starch – experiment

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Photosynthesis and respiration
Only green plants photosynthesize,
glucose
light energy
chlorophyll
carbon
Compare the reactants, products and energy results of
these two chemical reactions. How are they connected?
carbon
dioxide
glucose oxygen water
Photosynthesis
Respiration
but respiration occurs
in the cells of all living things to release energy.
(energy needed)
(energy released)

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12a.m. 12p.m. 12a.m.
Photosynthesis and respiration
How will the amounts of oxygen and carbon dioxide
in the air vary over 24 hours?
What overall effect do photosynthesis and respiration have
on the levels of oxygen and carbon dioxide in the air?
amount
of gas
in the air
amount of
oxygen
amount of
carbon dioxide

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Plant Nutrition
Contents

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Photosynthesis is a chemical reaction and so has a rate.
Is the rate of photosynthesis always the same?
light
glucose
light energy
chlorophyll
carbon
The rate of photosynthesis varies depending on three
main factors:
How do these factors affect the rate of photosynthesis?
carbon dioxide temperature

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Light and the rate of photosynthesis
Light energy has to be absorbed by chlorophyll
for photosynthesis to take place.
glucose
light energy
chlorophyll
carbon
The brighter the light, the more light energy there is,
so will photosynthesis be faster or slower?
More light energy means that photosynthesis will be faster.
If light intensity is too high plant cells can be damaged.
How is photosynthesis affected if this happens?

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Investigating photosynthesis – apparatus

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Investigating photosynthesis – experiment

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Investigating photosynthesis – results

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Carbon dioxide is one of the raw materials
used by plants to make their food.
Carbon dioxide and the rate of photosynthesis
glucose
light energy
chlorophyll
carbon
The concentration of carbon dioxide in the air (0.03%)
is actually quite low.
Why is the concentration of carbon dioxide in
commercial greenhouses often raised to about 0.1%?
More carbon dioxide means more photosynthesis,
so plants make more food and grow quicker.

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Photosynthesis is controlled by enzymes.
Enzymes usually work best at warmer temperatures.
Temperature and the rate of photosynthesis
glucose
light energy
chlorophyll
carbon
Why is the rate of photosynthesis slower on a sunny day
in winter compared to in summer?
If the temperature gets too hot (above 40°C), plant enzymes
begin to break down and are destroyed or denatured.
Why does photosynthesis stop under such conditions?

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What is the ideal combination of factors
for the maximum rate of photosynthesis?
What is a limiting factor?
enough light
enough carbon dioxide
ideal temperature (not too hot or cold)
How is the rate affected if one of these factors is restricted?
If one of the factors is restricted, the rate of photosynthesis
will be below the maximum possible rate.
The restricted factor controls how quickly photosynthesis
occurs and so limits the rate.It is called the limiting factor.

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Photosynthesis and light – limiting factors
How does the amount of light affect the rate
of photosynthesis on this labelled graph?
As the amount of light
increases, so does the rate.
The limiting factor is light.
light intensity
rate
of
photosynthesis
Here, increasing the amount
of light has no affect on the
rate. The limiting factor is
now carbon dioxide or
temperature.
What must be increased for
the rate to increase?
1
2
1
2

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Photosynthesis and carbon dioxide – limiting factors
How does the amount of carbon dioxide affect
the rate of photosynthesis on this labelled graph?
As the amount of carbon
dioxide goes up, so does
the rate. The limiting
factor is carbon dioxide.
concentration of
carbon dioxide
rate
of
photosynthesis
Here, increasing the
amount of carbon dioxide
has no affect on the rate.
Light or warmth is now
the limiting factor.
What must be increased
for the rate to increase?
1
2
1
2

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Photosynthesis and temperature – limiting factors
How does temperature affect the rate of
photosynthesis on this labelled graph?
1. As temperature increases,
so does the rate because
photosynthetic enzymes
work best in the warmth.
Here, the limiting factor is
temperature.
temperature
rate
of
photosynthesis
0oC 45oC
Most plant enzymes are
destroyed at about 45°C.
Here, photosynthesis stops
and the rate falls to zero.
What is the limiting factor?
1
2
1
2

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Limiting factors activity

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Limiting factors in the greenhouse

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Plant Nutrition
Contents

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What do plants need for a balanced diet?
Plants need carbon dioxide and water for photosynthesis.
Do they need any other nutrients to keep healthy?
Just like humans, plants need a balanced diet
that includes small amounts of mineral elements.
What mineral elements do they need?

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What minerals do plants need?
Plants need mineral elements for healthy growth.
Some of the most important minerals needed by plants are:
The mineral elements are found in salts dissolved in water.
Plants obtain minerals when they absorb water from the soil.
How do plants obtain these minerals?
nitrogen
potassium ions
phosphorus
potassium
magnesium magnesium ions
phosphates
nitrates
What type of salt are each of these elements found in?

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What are minerals needed for?
How do plants use these mineral elements?
Mineral element How mineral is used in plants
nitrogen (N)
phosphorus (P)
potassium (K)
magnesium (Mg)
making leaves
making roots
making flowers and fruit
making chlorophyll

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Plant and minerals – summary activity

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Where do minerals come from?
Rocks: The minerals in rocks are
slowly dissolved by slightly acidic
rainwater. These minerals are
washed into the soil.
Natural fertilizers: Animal faeces
and the decay of dead plants and
animals return minerals to the soil.
Artificial fertilizers: These
contain a ready-made mixture
of the minerals needed by plants.
What are the sources of minerals in the soil?
Why do farmers add fertilizers to their soil?

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Not enough minerals!
What happens if plants do not get enough minerals?
Plants do not grow properly if they are deprived of minerals
and begin to look unhealthy.
If a plant does not get enough of a mineral it is said
to have a mineral deficiency.
Do mineral deficiencies affect a plant in the same way?

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Mineral deficiency – no nitrogen!
Nitrogen is used for making leaves and is probably
the most important mineral for plant growth.
What is the effect of nitrogen deficiency?
lower leaves
yellow and dead
weak stem
upper leaves
pale green

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Mineral deficiency – no phosphorus!
Phosphorus is used for making roots and is important
for all the other minerals used by plants.
What is the effect of phosphorus deficiency?
small roots
purple leaves

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Mineral deficiency – no potassium!
Potassium is used for making flowers and fruit, so
crops are given extra potassium before they start to fruit.
What is the effect of potassium deficiency?
poor flower
and fruit growth
yellow leaves
with dead spots

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Mineral deficiency – no magnesium!
Magnesium is used for making chlorophyll
and so is vital for the process of photosynthesis.
What is the effect of magnesium deficiency?
upper leaves normal
(leaves turn yellow
from bottom upwards)
lower leaves pale green
or yellow

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Mineral deficiency experiment

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Plant and minerals summary
Mineral Use in plant Deficiency signs
nitrogen
phosphorus
potassium
magnesium
Complete this table of plant mineral needs and deficiencies.
making leaves
making roots
making flowers
and fruits
making chlorophyll
stunted growth and
yellow leaves
poor roots and
purple leaves
yellow leaves with
dead spots
leaves turn yellow
from the bottom

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Plant Nutrition
Contents

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Plant Pre-learning notes.ppt

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