Transcript Year10 photosynthesis1x

Flowering Plants
Flower
Leaf
Stem
Roots
1
A Leaf
Lamina
Midrib
Vein
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Leaf Structure
Waxy cuticle
Epidermis
Palisade mesophyll layer
Air spaces
Spongy mesophyll layer
Stoma
Epidermis
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Waxy Cuticle & Epidermis
Waxy cuticle
Epidermis
The waxy cuticle is a thin layer
atop the epidermis.
Its function is to reduce the water
lost from the leaf.
In arid conditions this cuticle layer
can be quite thick.
Epidermis cells contain no
chloroplasts – not true of the
stoma cells.
They form layers on the upper and
lower surfaces of the leaf.
Their function is to prevent water
getting out and stopping unwanted
substances/organisms getting in.
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Palisade Mesophyll Layer
The palisade mesophyll layer is
where most of the photosynthesis
occurs in the leaf.
Palisade mesophyll layer
The palisade cells contain a lot of
chloroplasts to help them perform
this photosynthesis.
The palisade cells are closely
packed together to maximize light
absorption.
In the leaf cross-section shown the
palisade cells are only found in the
upper part of the leaf.
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Spongy Mesophyll Layer
The cells in the spongy mesophyll
layer are not as closely packed as
the cells in the palisade mesophyll
layer.
This creates air spaces inside the
leaf to enable gases to move in
and out.
Spongy mesophyll layer
There are not as many chloroplasts
in the spongy mesophyll cells as
there are in the palisade mesophyll
cells – but photosynthesis still
occurs in the spongy mesophyll
layer.
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Stomata
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Stomata
There are holes found in leaves
called stomata.
These holes allows gases to
diffuse in and out of the leaves.
A stoma is formed by two highly
specialized epidermis cells.
These cells, called guard cells, are
the only epidermis cells that contain
chloroplasts.
The stomata open and close
depending upon the requirements of
the plant.
It is through these stomata that water
leaves the leaf, the process that
powers transpiration.
Stoma
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Stomata
Stoma open
During photosynthesis
carbon dioxide diffuses in
and oxygen diffuses out
Stoma closed
When the stomata are
closed,often at night or in
a humid environment, this
stops gases diffusing in
and out of the leaf
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Key Words
Waxy cuticle
Waterproof layer atop the epidermis
Stomata
Pores that allow gaseous exchange
Air spaces
Found in the spongy mesophyll layer,
enable gases to reach the leaf cells
Epidermis
One-cell thick outer layer of cells that
prevent water loss from the leaf
Palisade
mesophyll cell
Contain numerous chloroplasts and are
densely packed
Spongy
mesophyll cell
Loosely packed cells that do not contain
as many chloroplasts as palisade cells
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Photosynthesis
Chloroplasts are organelles of plant cells that contain a green
substance called chlorophyll.
Scientists believe chlorophyll absorbs light energy and this
energy is then used to make food.
The raw materials of photosynthesis are carbon dioxide and
water. The waste product of this reaction is oxygen.
The carbon dioxide required is absorbed through the stomata
in the leaves – this is how the oxygen is also removed.
The water required is absorbed by the roots.
The word equation for this reaction is...
The chemical equation for this reaction is...
6H2O + 6CO2  C6H12O6 + 6O2
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Photosynthesis
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Photosynthesis
Gaseous
Exchange
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Photosynthesis
Gaseous
Exchange &
Water
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Investigating Photosynthesis
Chlorophyll makes leaves green, but is
chlorophyll required for photosynthesis?
Your teacher will give you two leaves,
one is completely green.
The other leaf is called a variegated leaf.
The areas that are not green contain little
or no chlorophyll.
Both leaves have previously been destarched.
Do you know how to destarch a leaf?
Plan an investigation to discover if chlorophyll is required for
photosynthesis.
How will you test to see if photosynthesis has occurred?
What do you predict your results will be?
What apparatus will you require?
What safety precautions will you need to observe?
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Investigating Photosynthesis
Is carbon dioxide required for photosynthesis?
Your teacher will give you two plants, one is
enclosed in plastic and contains a chemical
that absorbs carbon dioxide.
Plan an investigation to discover if carbon
dioxide is required for photosynthesis.
What do you predict your results will be?
What apparatus will you require?
Why are two plants used?
How will you evaluate your results?
What chemical will you use to
remove carbon dioxide?
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Investigating Photosynthesis
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Using Plants
Humans have used plants for thousands of years.
There are many different uses of plants by humans. The
cotton plant shown is used to produce cotton for clothing etc.
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Exercise 1: Complete the Table
Stem
Root
Leaf
Flower
Rhubarb
Potato
Lettuce
Broccoli
Celery
Turnip
Cabbage
Cauliflower
Carrot
Broccoli
Rhubarb
Potato
Turnip
Celery
Lettuce
Cabbage
Cauliflower
Carrot
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Exercise 2: The Leaf
1. _____
Vein
2. Lamina
______
3. _______
Midrib
Midrib
Extension of the stalk into the leaf
Vein
The blade of the leaf
Lamina
Attaches the leaf to the stem
Stalk
Branch-off from the midrib
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Exercise 3: Label the Parts of a Plant
1. _______
Flower
2. _______
Leaves
3. _____
Stem
4. ______
Roots
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Exercise 4: Label the Parts of a Plant
Leaf
Roots
Stem
Flower
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Exercise 5: Leaf Structure
1. ___________
Waxy cuticle
2. ___________
Epidermis
3. ______________________
Palisade mesophyll layer
4. __________
Air space
5. _____________________
Spongy mesophyll layer
6. ________
Stoma
7. __________
Epidermis
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Exercise 6: Link the Boxes
Waxy cuticle
Pores that allow
gaseous exchange
Stomata
Found in the spongy
mesophyll layer, enable
gases to reach the leaf
cells
Air spaces
Waterproof layer atop
the epidermis
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Exercise 7: Link the Boxes
Epidermis
Palisade
mesophyll cell
Spongy
mesophyll cell
Loosely packed cells that do
not contain as many
chloroplasts as palisade cells
One-cell thick outer layer
of cells that prevent
water loss from the leaf
Contain numerous
chloroplasts and are densely
packed, where most of the
photosynthesis occurs
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Exercise 8: Short Questions - Leaf
1. What do we call the continuation of the leaf stalk into the leafblade?
Midrib
2. What do we call the specially adapted cells that form holes in the
leaves to allow gaseous exchange?
Guard cells
3. What are these holes/pores called?
Stomata
4. What is the name of the waxy waterproof layer found on top of the
epidermis?
Cuticle
5. What is the lamina?
The leaf-blade
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Exercise 9: Short Questions - Leaf
1. What do we call the outer one-cell thick layer of cells that contain
no chloroplasts?
The epidermis
2. What is the function of this layer?
To prevent water loss and to stop substances and
organisms entering the leaf
3. What are two differences between palisade mesophyll cells
(PMC) and spongy mesophyll cells (SMC)?
SMC – more loosely packed, less chloroplasts
PMC – more densely packed, more chloroplasts
4. By what process does carbon dioxide enter and leave leaves?
Diffusion
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Exercise 10: Insert the Missing Words
Chloroplasts __________
organelles of plant cells that contain a green
substance called __________.
chlorophyll
Scientists believe chlorophyll absorbs _____
light energy and this
energy is then used to make _____.
food
The raw materials of photosynthesis are carbon dioxide and
_____. This waste product of this reaction is _______.
water
oxygen
The carbon dioxide required is absorbed through the _______
stomata
in the leaves – this is how the oxygen is also removed.
The water required is absorbed by the roots
_____.
roots
organelles
light
food
water
chlorophyll
oxygen
stomata
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Exercise 11: Short Questions - Photosynthesis
1. Which organelles in plant cells contain a green substance called
chlorophyll?
Chloroplasts
2. Which two raw materials are required by green plants for
photosynthesis?
Water and carbon dioxide
3. What is the waste product of photosynthesis?
Oxygen
4. How does this waste product leave the plant during the day?
Through the stomata
5. What process requires this waste product to enable green
plants to release energy from their food?
Respiration
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Exercise 12: Short Questions – Plant Nutrition
1. What do we call the process whereby green plants make
glucose using light energy and the raw materials carbon dioxide
and water?
Photosynthesis
2. During the night many green plants perform another process
whereby they release the energy from their food they have
made. What do we call this process?
Respiration
3. The sugar glucose, the product of photosynthesis, is changed to
starch when it is being stored by the plant. Why?
Glucose is soluble in water, starch is insoluble in water.
By storing the food starch it means it is easier for the
plant to keep the food in the required place
4. What is the chemical formula of glucose?
C6H12O6
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Exercise 13: Short Questions – Plant Nutrition
1. What is the word equation for photosynthesis?
2. What is the chemical equation for photosynthesis?
6H2O + 6CO2  C6H12O6 + 6O2
3. Name the arrowed organelle.
Chloroplast
4. Which substance does this organelle
contain that allows green plants to
absorb the Sun’s light energy for the
process of photosynthesis?
Chlorophyll
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Exercise 14: Variegated Leaf
A destarched variegated plant was left in a sunny garden during
the day for several hours.
At the end of this period a leaf was taken from the plant and
tested for starch.
The results are shown below…
Variegated leaf
before starch test
Explain the result observed
Variegated leaf
after starch test
(8 marks)
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Exercise 15: Products of Photosynthesis
Some destarched pondweed was set-up as below.
A bright lamp was placed nearby for two hours.
The following results were observed at the end of this period.
Before lamp
turned on
Explain the result observed
After six hours of
lamp shining
(6 marks)
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Exercise 16: Short Questions
1. What is a variegated leaf?
Parts of the leaf do not contain chlorophyll, other parts do
2. Draw a diagram of a variegated leaf.
3. What is the chemical test for starch?
Starch turns orange/brown iodine solution purple/black
4. How do you destarch a green plant?
You leave it in the dark for several days so that its food
stores (starch) are exhausted
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Exercise 17: Label the Leaf Parts
A
C
B
A. _______________
Lamina
Vein
B. _______________
Midrib
C. _______________
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Interactive 1
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Interactive 2
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Interactive 3
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Interactive 4
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Interactive 5
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Interactive 6
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Interactive 7
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Interactive 8
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Interactive 9
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Interactive 10
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Interactive 11
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Interactive 12
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Interactive 13
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Interactive 14
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Interactive 15
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