Ch-6 of IGCSE Biology

1. Plants Nutrition

2. Content
 Photosynthesis
 Energy for the reaction
 Raw materials
 Products of the reaction
 Word equation
 Chemical equation
 Structure of leave
 Stomata
 The rate of photosynthesis
 Carbon dioxide
 Light
 Temperature
 Limiting Factors
 Carbon dioxide-limiting Factors
 Light-limiting Factors
 Temperature-limiting Factors
 Minerals Dificiency
 Nitrogen
 Phosphorus
 Potassium
 Magnesium
 Fertilisers (NPK)
 Greenhouse production
 Reference
 Questions

3. How do plants get the food they need?
All living organisms need food to grow and survive.
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?

4. 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

5. Plants make their own food by photosynthesis.
This process is a chemical reaction that uses light energy.
What is photosynthesis?
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?

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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
light
energy
chlorophyll
oxygen
glucose

12. Photosynthesis: summary
Summarize the process of photosynthesis in one sentence.
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.

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

14. Photosynthesis: chemical formulae?
Photosynthesis is a chemical reaction involving molecules.
glucose
light energy
chlorophyll
carbon
dioxide water oxygen
CO2 H2O O2C6H12O6

15. 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.

16. Leave Inner Structure

17. Stomata
 Stomata is a pore, found in
the epidermis of leaves,
stems and other organs that
is used to control gas
exchange.
 The pore is bordered by a
pair of specialized
parenchyma cells known as
guard cells that are
responsible for regulating the
size of the opening.
 Open in the morning.
 Close at night.

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

20. Light and the rate of photosynthesis
Light energy has to be absorbed by chlorophyll
for photosynthesis to take place.
glucose
light energy
chlorophyll
carbon
dioxide water oxygen
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?

21. 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
dioxide water oxygen
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.

22. Photosynthesis is controlled by enzymes.
Enzymes usually work best at warmer temperatures.
Temperature and the rate of photosynthesis
glucose
light energy
chlorophyll
carbon
dioxide water oxygen
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?

23. What is a limiting factor?
 A factor present in an environment that controls a
process, particularly the growth, abundance or
distribution of a population of organisms in an
ecosystem.

24. 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
rateofphotosynthesis
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

25. 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
rateofphotosynthesis
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

26. 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
rateofphotosynthesis
0o
C 45o
C
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

27. 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?

28. 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

29. 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?

30. 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.

31. 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

32. 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

33. 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

34. 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

35. Fertilisers (NPK)
• Fertilisers make crops grow
faster and bigger so that crop
yields are increased. They're
minerals, which must first
dissolve in water so that
plants can absorb them
through their roots.
• Fertilisers provide plants with
the essential chemical
elements needed for growth
particularly nitrogen,
phosphorus and potassium.
The proportions of these
elements in a fertiliser are
often shown as N:P:K =
15:30:15.

36. Greenhouse production
 Farmers can use their knowledge of factors limiting the rate of
photosynthesis to increase crop yields.
 This is particularly true in greenhouses, where the conditions are more
easily controlled than in the open air outside:
 The use of artificial light allows photosynthesis to continue beyond
daylight hours. Bright lights also provide a higher-than-normal light
intensity.
 The use of artificial heating allows photosynthesis to continue at an
increased rate.
 The use of additional carbon dioxide released into the atmosphere inside
the greenhouse also allows photosynthesis to continue at an increased
rate.

37. Reference
• www.google.com
• https://www.google.co.th/search?
q=fertilisers+npk&espv=2&biw=1366&bih=623&source=lnm
s&tbm=isch&sa=X&ei=ZPFAVZ-
wOY6juQShn4H4Dg&ved=0CAcQ_AUoAQ#tbm=isch&q=fer
tilisers+
• http://feeco.com/npk-fertilizer-what-is-it-and-how-does-it-
work/
• http://www.bbc.co.uk/schools/gcsebitesize/science/add_gate
way_pre_2011/chemical/fertilisersrev1.shtml
• http://en.wikipedia.org/wiki/Fertilizer
• www.bbcbitesize.com
• Biology for Cambridge IGCSE (Book)
• Others Books for Biology IGCSE

38. Plant and minerals (Question)
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

39. Questions
1. Write down the balanced chemical equation for
photostnthesis. On the equation identify the sources of
energy, raw material, and by-product.
2. Write down the word equation for photosynthesis
3. Define:
 Limiting factor
 Stomata
 Fertilisers
 NPK

40. Label the parts of inner structure of leave.

41. Thanks for your attention
Hope u all understand :)
Done By: Faiq & Rizan