1. Leaf Structure and Photosynthesis
Palisade cell
Stoma
Photosynthesis

2. Flowering Plants
Flower
Leaf
Stem
Roots

3. The Leaf
Vein
Lamina
Midrib
Stalk

4. The Leaf – Cross-section
Vein
Lamina
Midrib
Midrib
Extension of the stalk into the leaf
Vein
Branch-off from the midrib
Lamina
The blade of the leaf
Stalk
Attaches the leaf to the stem

5. Palisade mesophyll layer Spongy mesophyll layer
Leaf Structure
Waxy cuticle
Epidermis
Palisade mesophyll layer
Air space
Spongy mesophyll layer
Stomata
Epidermis

6. 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 ca 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.

7. 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.

8. 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.

9. Stomata There are holes found in leaves called stoma.
These holes allows gases to diffuse in and out of the leaves.
The stoma are formed by two highly specialized epidermis cells.
These cells, called guard cells, are the only epidermis cells that contain chloroplasts.
The stoma open and close depending upon the requirements of the plant.
It is through these stoma that water leaves the leaf, the process that powers transpiration.
Stomata

10. Stomata Stomata open Stomata closed
During photosynthesis carbon dioxide diffuses in and oxygen diffuses out
When the stoma are closed,often at night or in a humid environment, this stops gases diffusing in and out of the leaf

11. Key Words Waxy cuticle Waterproof layer atop the epidermis Stoma
Pores that allow gaseous exchange
Found in the spongy mesophyll layer, enable gases to reach the leaf cells
Air spaces
One-cell thick outer layer of cells that prevent water loss from the leaf
Epidermis
Palisade mesophyll cell
Contain numerous chloroplasts and are densely packed
Loosely packed cells that do not contain as many chloroplasts as palisade cells
Spongy mesophyll cell

12. 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 stoma 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

13. 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?

14. 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?

15. Exercise 1: Complete the Table
Stem
Root
Leaf
Flower
Rhubarb
Potato
Lettuce
Broccoli
Celery
Turnip
Cabbage
Cauliflower
Carrot
Rhubarb
Broccoli
Celery
Turnip
Potato
Lettuce
Cauliflower
Cabbage
Carrot

16. Exercise 2: The Leaf 1. _____ Vein 2. ______ Lamina 3. _______ 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

17. Exercise 3: Label the Parts of a Plant
1. _______
Flower
2. _______
Leaves
3. _____
Stem
4. ______
Roots

18. Exercise 4: Label the Parts of a Plant
Leaf
Roots
Stem
Flower

19. Exercise 5: Leaf Structure
1. ___________
Waxy cuticle
2. ___________
Epidermis
3. ______________________
Palisade mesophyll layer
4. __________
Air space
5. _____________________
Spongy mesophyll layer
6. ________
Stomata
7. __________
Epidermis

20. Exercise 6: Link the Boxes
Pores that allow gaseous exchange
Waxy cuticle
Found in the spongy mesophyll layer, enable gases to reach the leaf cells
Stoma
Waterproof layer atop the epidermis
Air spaces

21. Exercise 7: Link the Boxes
Loosely packed cells that do not contain as many chloroplasts as palisade 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, where most of the photosynthesis occurs
Spongy mesophyll cell

22. Exercise 8: Short Questions - Leaf
1. What do we call the continuation of the leaf stalk into the leaf-blade?
2. What do we call the specially adapted cells that form holes in the leaves to allow gaseous exchange?
3. What are these holes/pores called?
4. What is the name of the waxy waterproof layer found on top of the epidermis?
5. What is the lamina?
Midrib
Guard cells
Stoma
Cuticle
The leaf-blade

23. Exercise 9: Short Questions - Leaf
1. What do we call the outer one-cell thick layer of cells that contain no chloroplasts?
2. What is the function of this layer?
3. What are two differences between palisade mesophyll cells (PMC) and spongy mesophyll cells (SMC)?
4. By what process does carbon dioxide enter and leave leaves?
The epidermis
To prevent water loss and to stop substances and organisms entering the leaf
SMC – more loosely packed, less chloroplasts
PMC – more densely packed, more chloroplasts
Diffusion

24. Exercise 10: Insert the Missing Words
Chloroplasts __________ of plant cells that contain a green substance called __________.
Scientists believe chlorophyll absorbs _____ energy and this energy is then used to make _____.
The raw materials of photosynthesis are carbon dioxide and _____. This waste product of this reaction is _______.
The carbon dioxide required is absorbed through the ______ in the leaves – this is how the oxygen is also removed.
The water required is absorbed by the _____.
organelles
chlorophyll
light
food
water
oxygen
stoma
roots
roots organelles light food
water chlorophyll oxygen stoma

25. Exercise 11: Short Questions - Photosynthesis
1. Which organelles in plant cells contain a green substance called chlorophyll?
2. Which two raw materials are required by green plants for photosynthesis?
3. What is the waste product of photosynthesis?
4. How does this waste product leave the plant during the day?
5. What process requires this waste product to enable green plants to release energy from their food?
Chloroplasts
Water and carbon dioxide
Oxygen
Through the stoma
Respiration

26. 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?
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?
3. The sugar glucose, the product of photosynthesis, is changed to starch when it is being stored by the plant. Why?
4. What is the chemical formula of glucose?
Photosynthesis
Respiration
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
C6H12O6

27. Exercise 13: Short Questions – Plant Nutrition
1. What is the word equation for photosynthesis?
2. What is the chemical equation for photosynthesis?
3. Name the arrowed organelle.
4. Which substance does this organelle contain that allows green plants to absorb the Sun’s light energy for the process of photosynthesis?
6H2O + 6CO2  C6H12O6 + 6O2
Chloroplast
Chlorophyll

28. 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
Variegated leaf after starch test
Explain the result observed (8 marks)

29. 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
After six hours of lamp shining
Explain the result observed (6 marks)

30. Exercise 16: Short Questions
1. What is a variegated leaf?
2. Draw a diagram of a variegated leaf.
3. What is the chemical test for starch?
4. How do you destarch a green plant?
Parts of the leaf do not contain chlorophyll, other parts do
Starch turns orange/brown iodine solution purple/black
You leave it in the dark for several days so that its food stores (starch) are exhausted