Transport in plants

Question 1

What plant tissues transport material in a plant

Answer 1

The xylem and phloem

Question 2

What is the xylem

Answer 2

A plant tissue which transports water from the root to the stem and leaves

Question 3

What is the phloem

Answer 3

A plant tissue which transports food materials (mainly sucrose and amino acids) to the entire plant

Question 4

How is the xylem adapted for water transport

Answer 4

• Cells are joined end-to-end with no cross walls to form a continuous tube
• Cells are dead, no cell content, allowing for free passage of water
• Outer walls thickened with lignin. This strengthens the tube and supports the plant structure

Question 5

What is a root hair cell

Answer 5

• The root hair is a single-celled extension of the epidermis cell
• It absorbs water by osmosis and minerals from the soil by active transport
• The root hair increases the surface area of the cell which increases the rate of absorption by osmosis and active transport

Question 6

In order, what is the movement of water like in plants

Answer 6

1. Root hair cell
2. Root cortex cell
3. Xylem
4. Leaf mesophylls

Question 7

Give each step for investigating the movement of water in plants

Answer 7

1. Place a plant (like celery) in a beaker of water containing dye
2. Leave the plant for a few hours
3. The plant should turn the same colour as the dye which proves that the plant has absorbed the water
4. Cut a cross-section of the plant
5. You will see that not all of the area is dyed, which shows that water is transported in specific vessels. These vessels are the xylem vessels

Question 8

What is transpiration

Answer 8

Transpiration is the loss of water vapour from plant leaves by evaporation of water at layers of mesophyll followed by the diffusion of water vapour through stomata

Question 9

What are the effects of transpiration

Answer 9

• They cool cells down
• They provide water for photosynthesis
• They transport mineral ions
• They provide water to keep cells turgid and support the plant structure

Question 10

What factors affect the rate of transpiration

Answer 10

• Temperature
  Water molecules have more kinetic energy
  Water vapour will evaporate from mesophyll and diffuse away faster
• Humidity
  The moisture (water vapour) in the surrounding air. Lower humidity leads to a higher concentration gradient
• Wind speed
  Provides good air flow which removes the water vapour from the air surrounding the leaf
  This sets up a concentration gradient between the air and the leaf, increasing water loss

Question 11

In order, what are the steps to test the effects of environmental factors on the rate of transpiration

Answer 11

Environmental factors include temperature and wind speed. We can test the effect of these factors using a leafy shoot

1. Cut a shoot underwater to prevent the xylem from absorbing any air and place it in a beaker of water
2. Seal any air gaps using Vaseline
3. Dry leaves
4. Remove capillary tube from the beaker of water to form a single air bubble, and then reconnect it back to the water
5. Setup the environmental factor you are investigating
6. Let the plant adapt to its new environment for 5 minute
7. Record the starting location of the air bubble
8. Leave for set period of time
9. Recording the end location of the air bubble
10. Change the wind speed or temperature depending on what you are measuring

1.1 Open the tap below reservoir to reset the air bubble

12. Repeat the experiment
13. The longer the distance travelled by the air bubble, the faster the rate of transpiration