1. Transport Systems in Plants
Mr G Davidson
National 5
Transport Systems in Plants

2. The Need for Transport
All organisms must exchange materials with their environment, e.g. oxygen, carbon dioxide, water, etc..
Smaller organisms can do this easier than larger organisms because they have a large surface area compared to their volume.
Wednesday, 14 November 2018
Mr G Davidson

3. The Need for Transport Height Breadth Length
If we imagine a cell takes the form of a cube, we can calculate the surface area, the volume, and, therefore, the SA:V ratio.
Length
Breadth
Height
Wednesday, 14 November 2018
G Davidson

4. The Need for Transport We first need to calculate the surface area:
Surface area = Length x Breadth x number of sides
Surface area is measured in cm2
We now need to calculate the volume:
Volume = Length x breadth x height
Volume is measured in cm3
Wednesday, 14 November 2018
G Davidson

5. We can now work out the ratio:
The Need for Transport
We can now work out the ratio:
Surface area : Volume
e.g. if the cube has sides 1cm long:
Surface area = 1 x 1 x 6
So S.A. = 6 cm2
Volume = 1 x 1 x 1
So V = 1 cm3
S.A. : V
Therefore:
=6 : 1
Wednesday, 14 November 2018
G Davidson

6. The Need for Transport Length of side S.A. (cm2) Volume (cm3) S.A. : V1 6
6:1 2 3 4 5
Complete the table.
Wednesday, 14 November 2018
G Davidson

7. The Need for Transport Length of side S.A. (cm2) Volume (cm3) S.A. : V1 6
6:1 2 24 8
3:1 3 54 27
2:1 4 96 64
3:2 5
150
125
6:5
216
1:1
Complete the table.
Wednesday, 14 November 2018
G Davidson

8. The Need for Transport
By comparing the cubes in the table, we can now see that as an organism increases in size, it’s surface area: volume ratio actually decreases.
This makes it more difficult to exchange materials with the environment.
Wednesday, 14 November 2018
Mr G Davidson

9. The Need for Transport
Once these materials have entered an organism, they must be distributed throughout all of the cells.
In unicellular and very small organisms, this can be achieved by diffusion.
In multicellular and larger organisms a specialised transport system is required to move materials around the organism.
Wednesday, 14 November 2018
Mr G Davidson

10. The Need for Transport
In the case of a plant, water has to be moved around for transporting minerals as well as being used up in the leaves by photosynthesis.
Water enters the plant through the root hairs buried in the soil by osmosis.
Wednesday, 14 November 2018
Mr G Davidson

11. The Need for Transport
Wednesday, 14 November 2018
Mr G Davidson

12. The Need for Transport
As the water moves in, it diffuses into the cell next to the root hair and from there into the next one.
The water will eventually reach the xylem vessel which will transport the water up through the stem to the rest of the plant.
Wednesday, 14 November 2018
Mr G Davidson

13. The Need for Transport
Wednesday, 14 November 2018
Mr G Davidson

14. The Need for Transport
Because water is continually being used up in the leaves by photosynthesis, it has to be replaced with water from below.
This movement of water up through the plant is called the transpiration stream.
Wednesday, 14 November 2018
Mr G Davidson

15. The Need for Transport
Some of this water is lost from the leaf surfaces by evaporation and this is called transpiration.
Most of this transpiration takes place through tiny pores on the leaf surface called stomata. (Stoma – singular)
Wednesday, 14 November 2018
Mr G Davidson

16. The Need for Transport
Xylem vessels are like pipes made of dead hollow cells.
They are inlaid with a waterproof substance called lignin which helps to support the vessels.
The lignin can either be laid down in rings (annular) or in spirals.
Wednesday, 14 November 2018
Mr G Davidson

17. Xylem Vessels Spiral lignin Annular lignin Spiral lignin Xylem Vessel
Wednesday, 14 November 2018
Mr G Davidson

18. Leaf Structure Waxy Cuticle Upper Epidermis Palisade mesophyll
Spongy mesophyll
Vascular bundle
Lower Epidermis
Stoma
Guard cell
Wednesday, 14 November 2018
Mr G Davidson

19. Leaf Structure Part of Leaf Function Waxy Cuticle
Cuts down water loss by evaporation
Upper Epidermis
Protection. These cells have no chloroplasts
Palisade mesophyll
Main region of photosynthesis. These cells have many chloroplasts
Spongy mesophyll
Contains many air spaces to allow gases to circulate
Lower Epidermis
Protection. These cells also have no chloroplasts
Guard cells
Control the opening and closing of the stomata
Stomata
Pores through which gases can move in and out
Vascular bundle
Contains xylem and phloem which allow materials to be transported into and out of the leaves
Wednesday, 14 November 2018
Mr G Davidson

20. The Need for Transport
As well as the xylem vessels which transport water and minerals salts, there is also phloem vessels which are responsible for the transport of the sugars made by photosynthesis.
Together these tubes make up the vascular bundles.
Phloem is different from xylem in that phloem is made of living tissue.
Wednesday, 14 November 2018
Mr G Davidson

21. The Need for Transport
It is composed of sieve tubes and companion cells.
The cytoplasm of the sieve tubes passes through the sieve plates of the end walls so that it is continuous between the cells.
This allows the sugars to be transported all around the plant.
Wednesday, 14 November 2018
Mr G Davidson

22. Phloem Pores of sieve plate Sieve tube element Companion cell
Wednesday, 14 November 2018
Mr G Davidson

23. Leaf Surfaces Leaves take in carbon dioxide from the air.
In exchange they give out oxygen produced during photosynthesis.
These gases must be able to get in and out of a leaf.
Leaves have special structures which allow gas exchange.
These structures are called stomata.
Wednesday, 14 November 2018
Mr G Davidson

24. Stomata
Tiny pores on the surface of a leaf which allow gases in and out.
They also allow water to escape.
Each pore is a STOMA and is surrounded by 2 GUARD CELLS.
Wednesday, 14 November 2018
Mr G Davidson

25. Stomata
The guard cells are responsible for the opening and closing of the stomata.
It is brought about by the guard cells changing in turgor.
When they are full of water they become sausage shaped and therefore open the stomata.
This occurs during daylight.
At night, during darkness, water leaves the guard cells causing the stomata to close.
Wednesday, 14 November 2018
Mr G Davidson

26. Stomata
Wednesday, 14 November 2018
Mr G Davidson