Bio C8

Question 1

1. What does the xylem transport?

Answer 1

Water and minerals

Question 2

2. What does the phloem transport?

Answer 2

Sucrose and amino acid

Question 3

3. Draw the position of the xylem and phloem in the leaf, stem and root

Answer 3

Question 4

4. What type of plant cell does this diagram show? How are these cells adapted to their
   function?

Answer 4

A root hair cell
- Long root hair extension to increase surface area for uptake
- Thin membranes to decrease the diffusion distance

Question 5

5. Describe the pathway of water through a plant

Answer 5

Root hair cell → Root cortex cells → Xylem → Mesophyll cells

Question 6

6. Define transpiration

Answer 6

The evaporation of water from the aerial parts of a plant on the surface of the mesophyll cells
which is followed by diffusion of water vapour through the stomata

Question 7

7. Describe the process of transpiration

Answer 7

• Water is lost through the stomata
• More water is drawn up to replace the lost water

Question 8

8. Explain the movement of water through a plant

Answer 8

Water loss in leaves which lowers its water potential
Water moves from xylem to leaf tissues via osmosis
Water moves up the stem in the xylem due to tension (because of cohesion of water molecules to each other) caused by water loss from the leaves
Ends with the gain of water through roots
This upward flow of water is called the transpiration stream

Question 9

9. How does temperature, light intensity, wind speed and humidity affect the rate of transpiration?

Answer 9

• As the temperature increases, so does the transpiration rate
• The molecules have more kinetic energy and evaporation happens faster
• The brighter the light, the more stomata are open and the rate of photosynthesis
  increases which both decrease the amount of water in the plant
• The rate of transpiration increases
• The faster the wind speed, the faster the water is moved away from the plant, creating a steeper gradient and increasing the transpiration rate
  Humidity: lower humidity increases water potential gradient between leaf and atmosphere ∴ increasing transpiration rate

Question 10

10. Describe translocation

Answer 10

Translocation is the movement of sugars and amino acids up or down the phloem from source to sink