1. National 5 Biology Unit 2 – Cell Biology
Section 11
Transport in Plants

2. We will be learning how to…
Explain why multicellular organisms require transport systems
Explain why plants require a transport system for water
State the name for the movement of water through a plant
State the structures involved in the transport of water in plants
Describe the structure and function of xylem
Describe the function of guard cells
Describe the process of transpiration
Name environmental factors which increase the rate of transpiration in plants
Explain why plants require a transport system for sugar
State the structure involved in the transport of sugar in plants

3. Plant Transport Think –
What needs to be transported about inside plants?
We need to find out more about how it happens and the problems that arise.

4. Importance of transport systems
Plants need transport systems to supply the raw materials for photosynthesis and to remove the products.
Xylem
Phloem
Light
Carbon dioxide
Water
Glucose
Oxygen
Chlorophyll
Diffuse through stomata

5. Watch this clip http://youtu.be/w6f2BiFiXiM
Transpiration
Plants need water for photosynthesis.
It is absorbed in the roots and evaporated out of leaves.
Watch this clip
Water travels up from the roots in the xylem to the leaves. In the leaves it moves by osmosis from cell to cell and then evaporates into the gaps in the spongy mesophyll cells.
If the stomata are open the water vapour will diffuse out of the leaf. This is called transpiration.

6. Transpiration -water evaporates from leaves
Photosynthesis produces sugar in the leaves
Sugar is transported in phloem
The movement of water through the plant is called the transpiration stream
stem
roots
Water and ions pass up xylem
Mineral ions enter by active transport
Water enters roots by osmosis
National 4/5 Biology Course Unit 2

7. Transpiration - Transport of Water
lignin
xylem vessel

8. Long root hair to increase surface area
Root Hair Cell
Structure
Long root hair to increase surface area
Function
Collects water and mineral nutrients present in soil to transport this to the rest of the plant

9. Xylem
The role of the xylem is to transport water from the roots to all other areas of the plant.
The xylem plays an important role in the transport of minerals which are dissolved in the water.
It also helps strengthen the stem of the plant.
National 4/5 Biology Course Unit 2

10. Xylem
They have no cell contents and no nucleus. They are hollow tubes of dead cells.
The end walls have broken down and have disintegrated.
Side walls are strengthened by lignin to prevent damage by water pressure

11. The Structure of a Leaf Leaves
Leaves are adapted for photosynthesis by having a large surface area, and contain stomata (openings) to allow carbon dioxide into the leaf. These design features 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.

12. the protective outer layer of cells on the surface of a leaf.
Structure
Function
Epidermis
the protective outer layer of cells on the surface of a leaf.
Palisade Mesophyll
elongated cells located under the epidermis. contains most of the leaf’s chlorophyll.
Spongy Mesophyll
located below the palisade mesophyll. irregularly-shaped cells with many air spaces between. contains some chlorophyll.
Vein
contains a collection of xylem and phloem vessels.
Moist air space
gases dissolve in water vapour for photosynthesis.
Guard cells
control the opening and closing of stoma.
Stoma
openings in the surface of a leaf for gas exchange.

13. Stomata and Guard Cells
Turgid – full of water – stoma is open
Flaccid – stoma is closed
Guard cells surround each stoma. They regulate the rate of transpiration by opening and closing the stomata as the water is used up
Thin outer wall stretches more than thick inner wall
Walls not stretched

14. Transpiration Rate light temperature humidity wind
Various factors will affect the rate of transpiration.
This includes
light
temperature
humidity
wind

15. Using a Potometer – Measuring Transpiration

16. Phloem
As well as transporting water and minerals, plants have to transport the sugar from photosynthesis from the leaves to other parts of the plant.
This is carried out by special cells called phloem.
National 4/5 Biology Course Unit 2

17. Phloem
Columns of sieve tubes, connected by sieve plates at either end.
sieve tube
Companion cells sit next to the sieve tubes.
companion cell
They have a dense cytoplasm and a nucleus.
They are living cells.
sieve plates with pores
nearby cell

18. Stem Cross Section

19. Root Cross Section

20. Glossary
Xylem
transport water from the roots to all other areas of the plant.
Root Hair Cell
Collects water and mineral nutrients present in soil to transport this to the rest of the plant
Lignin
Structural material that supports the xylem tissues by lining the cell wall
Transpiration
explains how water moves up the plant against gravity in tubes made of dead xylem cells without the use of a pump.
Potometer
a device used for measuring the rate of water uptake of a leafy plant shoot. The main reason for water uptake by a cut shoot is transpiration (evaporation in plants) and is affected by the transpiration stream
Upper Epidermis
Thin layer to allow more light to reach the palisade cells
Mesophyll Layer
Contains many chloroplasts to absorb all the available light
Vein
a vascular structure (xylem and phloem cells surrounded by the bundle sheath) in a leaf that provides supports for the leaf and transports both water and food
Stoma
A pore that is used for gas exchange. They are mostly found on the under-surface of plant leaves.

21. Glossary
Guard Cells
These help to regulate the rate of transpiration by opening and closing the stomata
Moist air space
Increases surface area of leaf to absorb more carbon dioxide
Turgid
swollen
Flaccid
oft and hanging loosely or limply
Phloem
transports glucose from the leaves to the rest of the plant
Sieve Plates
pores in the plant cell walls that facilitate transport of materials between them
Sieve Tubes
living cells of the phloem, the nuclei have fragmented and disappeared and the end walls of which are pierced by sieve-like groups of pores (sieve plates). They transport sugar.
Companion Cell
It regulates the activity of the adjacent sieve tube and to take part in loading and unloading sugar into the sieve plate