Trilogy AQA Plant organs

1. Last Lesson Last Week
Last Term
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2. Last Lesson
How is a benign cancer
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3. B2 Specification

4. Plant Tissues and Organs
Learning outcomes
1. To be able to state the tissues and organs found in
plants.
2. To be able to describe how the tissues and organs in
plants are adapted to perform their functions
3. To be able to explain how the structure of the leaf
ensures that the maximum photosynthesis takes
place.

5. Plant Tissues and Organs
• Look at the diagram
of the plant.
• Which parts would
you label as tissues
and which would you
label as organs?

6. The Xylem and Phloem
• Plants are large and complex so, there are large distances between
roots and leaves.
• Every cell needs to respire and get raw materials as well as remove
waste…
• Plants make glucose in the leaves that needs to get to respiring cells
throughout the plant.
• Plants have a vascular system that creates a flow of water and minerals
into the plant (transpiration stream) and distributes it to the leaves –
Xylem vessels
• They have vessels that actively move glucose around to respiring cells
(translocation) in Phloem vessels.

7. Water passes from the soil water to the root hair cell’s cytoplasm by osmosis. This
happens because the soil water has a higher water potential than the root hair cell
cytoplasm:
Solution Water potential Concentration of dissolved solutes
Soil water High Low
Root hair cell cytoplasm Low High
Osmosis causes water to pass into the root hair cells, through the root cortex and
into the xylem vessels

8. The products of photosynthesis
have to be distributed
• The plant makes Glucose by
photsynthesis in the leaves.
• The main cells responsible for
photosynthesis are _________ mesophyll
cells.
• The glucose has to be moved into the rest
of the plant by active transport – it gets
translocated.

9. The movement of glucose in
plants requires energy.
• The phloem cells need to respire to
actively move sugar molecules against the
flow of diffusion.
• The xylem vessels are long fibrous tubes
that move the water by capillary action
from the roots up the plant.
• Water molecules are attracted to each
other and rise up the xylem vessels.

10. Plant Tissues and Organs
Summary Questions
Use your summary sheets to help you answer the following
questions:
1. List the tissues found in plants
2. List the organs found in plants.
3. What is the function of mesophyll tissue in plants
4. Why do leaves have a waxy layer?
5. Where on a leaf would you expect to find more stomata? –
Why are there more in this location?
6. Create a play on words that will help you to remember the
function of xylem and phloem in plants.

11. How leaves are adapted for photosynthesis?
________________
_____________
______________
_________
Xylem and phloem

12. 13/09/2022
Leaf Structure

13. Palisade cells
The top layer of cells in a leaf are
called the palisade leaf cells. They
are specially adapted to make the
most of the light conditions they
receive. So they have many more
Chloroplasts than other plant cells to
catch as much sunlight at possible
for photosynthesis.
Palisade cells are also more block
shaped so that many of them can be
packed into the top layer of the
leaf.
Extra challenge:
1. Why are palisade cells tall and thin (vertical),
rather than horizontal?
2. Why do root hair cells not have chloroplasts?

14. Spongy mesophyll
Spongy mesophyll cells are not
packed tightly together, which
allows carbon dioxide to reach the
palisade cells for photosynthesis.
This tissue contains irregularly
shaped cells with few chloroplasts.
Extra challenge:
1. On your diagram draw two arrows showing the movement of oxygen
and carbon dioxide? (Hint: What goes into the leaf and what comes
out?)
2. Why is there fewer chloroplasts than palisade cells?

15. Carbon dioxide and oxygen can’t just diffuse
into the leaf. They have to be let in through
special doors called stomata. Stomata are
usually concentrated on the bottom of the
leaf to limit water loss.
Guard cells are cells surrounding each stoma,
they open and close the stomata.
Guard cell and stomata

16. Waxy cuticle
The outer surface of the leaf
has a thin waxy covering called
the waxy cuticle, this prevents water
loss within the leaf by evaporation .
(Plants that live entirely in water do
not have a waxy cuticle).
Extra challenge:
1. Why is the waxy cuticle found on the top of the leaf and not at the
bottom? (Think about what increases evaporation?)
2. Why do plants that live in water not need a waxy cuticle?
3. How do you think the waxy cuticle for a plant found in the desert
would differ to that found in the UK?

17. Xylem and phloem
Plants 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 and phloem moves food substances
from leaves to the rest of the plant.
Xylem vessels are involved in the movement of water through a
plant from its roots to its leaves. Water:
• Is absorbed from the soil through root hair cells
• Is transported through the xylem vessels up the stem to the
leaves
• Evaporates from the leaves
Phloem
• Phloem vessels are involved in translocation. This is the
movement of food substances from the stems to growing
tissues and storage tissues.
Extra challenge:
1. Xylem transport water and mineral ions. What mineral ions do plants
need?