Leaf Structure and Photosynthesis

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Leaf Structure and Photosynthesis
Leaf structure Palisade cell Stoma Photosynthesis
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Flowering Plants
Flower
Leaf
Stem
Roots
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The Leaf
Vein
Lamina
Midrib
Stalk
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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
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Leaf Structure
Waxy cuticle
Epidermis
Palisade mesophyll layer
Air space
Spongy mesophyll layer
Stomata
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 we can see 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
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
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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
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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
Contain numerous chloroplasts and are densely
packed
Palisade mesophyll cell
Loosely packed cells that do not contain as many
chloroplasts as palisade cells
Spongy mesophyll cell
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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 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
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Exercise 1 The Leaf
1. _____
Vein
Lamina
2. ______
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 2 Label the Parts of a Plant
1. _______
Flower
2. _______
Leaves
3. _____
Stem
4. ______
Roots
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Exercise 3 Label the Parts of a Plant
Leaf
Roots
Stem
Flower
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Exercise 4 Leaf Structure
1. ___________
Waxy cuticle
2. ___________
Epidermis
3. ______________________
Palisade mesophyll layer
4. __________
Air space
5. _____________________
Spongy mesophyll layer
6. ________
Stomata
7. __________
Epidermis
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Exercise 5 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
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Exercise 6 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
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Exercise 7 Insert the Missing Words
Chloroplasts are __________ 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
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Exercise 8 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
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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? 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
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Exercise 10 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 Suns light energy for the
process of
photosynthesis?
6H2O 6CO2 ? C6H12O6 6O2
Chloroplast
Chlorophyll