Transcript Notes LeafStructure & Photosyn

Leaf Structure and Photosynthesis
Leaf structure
Palisade cell
Stoma
Photosynthesis
Flowering Plants
Flower
Leaf
Stem
Roots
Vein
Lamina
Midrib
Stalk
The Leaf
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
Leaf Structure
Waxy cuticle
Epidermis
Palisade mesophyll layer
Air space
Spongy mesophyll layer
Stomata
Epidermis
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.
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 we can see
the palisade cells are only found in
the upper part of the leaf.
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.
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
Stomata
Stomata open
Stomata closed
During photosynthesis
carbon dioxide diffuses in
and oxygen diffuses out
When the stomata are
closed,often at night or in
a humid environment, this
stops gases diffusing in
and out of the leaf
Key Words
Waxy cuticle
Waterproof layer atop the epidermis
Stoma
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
Photosynthesis
Chloroplasts are organelles of plant cells that contain a green
pigment 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
Exercise 1: 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
Exercise 2: Label the Parts of a Plant
1. _______
Flower
2. _______
Leaves
3. _____
Stem
4. ______
Roots
Exercise 3: Label the Parts of a Plant
Leaf
Roots
Stem
Flower
Exercise 4: Leaf Structure
1. ___________
Waxy cuticle
2. ___________
Epidermis
3. ______________________
Palisade mesophyll layer
4. __________
Air space
5. _____________________
Spongy mesophyll layer
6. ________
Stomata
7. __________
Epidermis
Exercise 5: Link the Boxes
Waxy cuticle
Pores that allow
gaseous exchange
Stoma
Found in the spongy
mesophyll layer, enable
gases to reach the leaf
cells
Air spaces
Waterproof layer atop
the epidermis
Exercise 6: 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
Exercise 7: Insert the Missing Words
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
_____. This waste product of this reaction is _______.
water
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
_____.
roots
organelles
light
food
water
chlorophyll
oxygen
stoma
Exercise 8: 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 stoma
5. What process requires this waste product to enable green
plants to release energy from their food?
Respiration
Exercise 9: 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
Exercise 10: 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