1. The Need For Transport - plants
Multicellular Organisms
- Section 6

2. Surface area:volume ratio
A single celled organism has a large surface area in relation to its volume
- most of it’s body tissue is close to the surface
- diffusion allows materials to get throughout the cell
Larger organisms have much less of their inner tissue close to the surface
- a transport system is needed to move substances to and from the surface

3. Learning Outcomes During this section you will be able to:
- explain the need for transport systems in plants
- describe the structures and processes involved in water and sugar movement
- explain the processes of transpiration and evaporation
* requires a review of photosynthesis from S3

4. Plant transport systems
Plants need two transport systems
1) xylem for water transport
- transports water from roots to leaves
2) phloem for sugar transport
- transports sugar from leaves to the roots

5. Water transport in a plant
Water enters plants by osmosis through root hair cells
- root hair presents a large surface area
Water then passes from cell to cell until it reaches the xylem
The xylem transports the water to the mesophyll cells
- where photosynthesis occurs

6. Exit of water Water is lost from a plant by transpiration
Most water leaves through the stomata
The guard cells get swollen (turgid) when water enters them
This opens the stoma
Allowing water to exit the plant
- occurs during daylight

7. Experiment
You will now carry out an experiment to assess what factors affect water loss (transpiration) the most
Factors that could have an affect include:
- wind
- humidity
- temperature