This document discusses photosynthesis and plant structures and processes related to photosynthesis. It describes how leaves are adapted through features like a large surface area, thinness, and chlorophyll to efficiently perform photosynthesis. These adaptations allow leaves to absorb sunlight, carbon dioxide, and produce carbohydrates. The document also discusses the transport systems in plants, including xylem and phloem, and how roots absorb water through osmosis and root hairs.

1. Photosynthesis
Thandi Radebe

2. A Plant Cell
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3. Which organisms can
produce their own food?
• autotrophs
• They use chloroplasts to create
food.
• Plants are autotrophs eg leafs and
flowers.

4. Leaves
• Flattened leaf shape exposes
large surface area to catch
sunlight
• Upper and lower leaf surfaces of
a leaf comprise the epidermis
• Waxy, waterproof cuticle on
outer surfaces reduces water
evaporation

5. Structure of a leaf
• The function of a leaf is photosynthesis – to absorb
light and carbon dioxide to produce carbohydrates. The
equation for photosynthesis is:
• Carbon dioxide and water → glucose and oxygen
• Did you know:
• Leaves are the source of all of food on the planet
• Leaves recycle all of the world's carbon dioxide in the
air
• Leaves contain the world's most abundant enzyme

7. Leaves are adapted in several ways to help them
perform their function.
Features of leaves
Adaption
Purpose
Large surface area
To absorb more light
Thin
Short distance for carbon dioxide
to diffuse into leaf cells
Chlorophyll
Absorbs sunlight to transfer
energy into chemicals
Network of veins
To support the leaf and transport
water and carbohydrates
Stomata
Allow carbon dioxide to diffuse into
the leaf

8. Structures of
Photosynthesis

9. Part of Chloroplasts & Chlorophyll

10. • The internal structure of the leaf is
also adapted to promote efficient
photosynthesis:
Adaption
Purpose
Epidermis is thin and transparent
To allow more light to reach the
palisade cells
Thin cuticle made of wax
To protect the leaf without blocking
out light
Palisade cell layer at top of leaf
To absorb more light
Spongy layer
Air spaces allow carbon dioxide to
diffuse through the leaf, and increase
the surface area
Palisade cells contain many
chloroplasts
To absorb all the available light

11. A nd T he Re su lt of
Ph otosynthesis :

12. Maximising growth
• Farmers can use their knowledge of these
limiting factors to increase crop growth in
greenhouses. They may use artificial light so
that photosynthesis can continue beyond
daylight hours, or in a higher-than-normal light
intensity. The use of paraffin lamps inside a
greenhouse increases the rate of
photosynthesis because the burning paraffin
produces carbon dioxide, and heat too.

13. Plant Transport
• No heart, no blood and no circulation, but
plants do need a transport system to move
food, water and minerals around. They use
two different systems – xylem moves water
and solutes from the roots to the leaves –
phloem moves food substances from leaves
to the rest of the plant. Both of these systems
are rows of cells that make continuous
tubes running the full length of the plant.

14. Xylem
• Xylem cells have extra reinforcement in
their cell walls, and this helps to support
the weight of the plant. For this reason, the
transport systems are arranged differently
in root and stem – in the root it has to resist
forces that could pull the plant out of the
ground. In the stem it has to resist
compression and bending forces caused by the
weight of the plant and the wind.

16. Plant Stem
• Stem – the xylem and phloem are
arranged in bundles near the edge of
the stem to resist compression and
bending forces.

17. Plant Root
• Root - xylem and phloem in the centre
of the root to withstand stretching
forces.

18. Comparison of xylem and phloem
Tissue
Process
What is moved
Structure
Xylem
Transpiration
Moves water and
minerals from
roots to leaves
Columns of
hollow, dead
reinforced cells
Phloem
Translocation
Moves food
substances from
leaves to rest of
plant
Columns of living
cells

19. Root hair cells
• Plants absorb water from the soil by osmosis. Root hair
cells are adapted for this by having a large surface area
to speed up osmosis.
• The absorbed water is transported through the roots to
the rest of the plant where it is used for different
purposes:
• It is a reactant used in photosynthesis
• It supports leaves and shoots by keeping the cells rigid
• It cools the leaves by evaporation
• It transports dissolved minerals around the plant

21. Leaves
• Leaves are adapted for photosynthesis by having a
large surface area, and contain openings,
called stomata to allow carbon dioxide into the leaf.
Although these design features are good for
photosynthesis, they can result in the leaf losing a lot of
water. The cells inside the leaf have water on their
surface. Some of this water evaporates, and the water
vapour can then escape from inside the leaf
by diffusion.
• To reduce loss the leaf is coated in a wax cuticle to
stop the water vapour escaping through the epidermis.
Leaves usually have fewer stomata on their top
surface to reduce this water loss.

23. Stomata
• Plants growing in drier conditions tend to have
small numbers of tiny stomata and only on
their lower leaf surface, to save water loss.
Most plants regulate the size of stomata
with guard cells. Each stoma is surrounded
by a pair of sausage-shaped guard cells. In
low light the guard cells lose water and
become flaccid, causing the stomata to close.
They would normally only close in the dark
when no carbon dioxide is needed for
photosynthesis.

25. Turgidity
• Most plant cells are turgid at all times. This
supports the weight of the plant, which is
especially important where there is no woody
tissue, such as leaves, shoot and root tip. If the
plant loses water faster than it can be absorbed
the cells lose turgor pressure and become
flaccid. This causes the plant to wilt.
• You should be able to explain why most plants
will wilt if they get flooded by sea water. (Hint:
sea water contains many chemicals in solution,
such as salt. Osmosis will move water across the
plant cell membrane, from the weaker to the
stronger solution.)

26. Turgidity

27. Osmosis
• Osmosis is the movement of water molecules
from an area of high concentration of water to
an area of lower concentration of water through
a partially permeable membrane. This can be the
cell membrane. An example is the flooding of
plants by sea water. Sea water contains many
chemicals in solution, such as salt. Osmosis will
move water across the plant cell membrane,
from the weaker to the stronger solution.

30. Light Dependent
Reaction

32. Reference list
http://www.slideshare.net/paprescott/photosynthesis-11319148?qid=0db35706-0545-46b2-bca62f65331639c2&v=default&b=&from_search=4
http://www.slideshare.net/HaziraUlfa/photosynthesis-13936288?qid=0db35706-0545-46b2-bca62f65331639c2&v=default&b=&from_search=5
http://www.slideshare.net/eestevez1/photosynthesis-11663780?qid=0db35706-0545-46b2-bca62f65331639c2&v=default&b=&from_search=10
http://www.slideshare.net/CyberScienceSchool/photosynthesis-2578837?qid=0db35706-054546b2-bca6-2f65331639c2&v=default&b=&from_search=6
http://www.slideshare.net/jordanramsey26051998/photosynthesis-26870799?qid=0db35706-054546b2-bca6-2f65331639c2&v=default&b=&from_search=12

33. Test
GOOD LUCK!!!!!

37. Answers