3.1.3 Transport in plants

Question 1

Look at the vascular bundle.
Which letter shows a xylem vessel?

Answer 1

D

Question 2

Name the four different cells that make up the xylem tissue.

Answer 2

• Vessels
• Tracheids
• Parenchyma
• Screlenchyma

Question 3

Which cell in the xylem tissue stores starch?

Answer 3

Parenchyma

Question 4

Transpiration is described as a “natural consequence” of gas exchange.
What does this mean?

Answer 4

Gas exchange happens through the stomata.
Transpiration occurs as a natural consequence of this process.

Question 5

What is transpiration?

Answer 5

When water evaporates from the surface of a leaf through the stomata

Question 6

What are three benefits of transpiration?

Answer 6

• Provides a cooling effect
• Transpiration stream allows plant to absorb more mineral ions through the roots
• Water in xylem increases turgor pressure, providing support to plant’s stem

Question 7

Why do stomata close at night?

Answer 7

Limits transpiration to prevent water loss.

Question 8

Name four factors that affect the rate of transpiration.

Answer 8

• Temperature
• Light intensity
• Humidity
• Wind speed / Movement of air

Question 9

This graph shows how which factor affects the rate of transpiration?

Answer 9

Temperature

Question 10

This graph shows how which factor affects the rate of transpiration?

Answer 10

Humidity

Question 11

This graph shows how which factor affects the rate of transpiration?

Answer 11

Air movement / Wind speed

Question 12

This graph shows how which factor affects the rate of transpiration?

Answer 12

Light intensity

Question 13

Name the meristem cells found in vascular bundles.

Answer 13

Cambium

Question 14

Which piece of equipment can be used to measure the rate of transpiration?

Answer 14

Potometer

Question 15

What is used to strengthen xylem walls?

Answer 15

Lignin

Question 16

This image shows the cross section of a stem.
What is the arrow pointing to?

Answer 16

Pith

Question 17

This image shows the cross section of a stem.
What is the arrow pointing to?

Answer 17

Phloem

Question 18

This image shows the cross section of a stem.
What is the arrow pointing to?

Answer 18

Cambium

Question 19

What is meant by the transpiration stream?

Answer 19

The continuous flow of water from the roots to the leaves.

Question 20

Water molecules are cohesive. What does this mean?

Answer 20

They form hydrogen bonds with other water molecules.

Question 21

Water molecules are adhesive. What does this mean?

Answer 21

They form hydrogen bonds with surfaces, e.g. the walls of the xylem.

Question 22

This image shows a meniscus.
Does a meniscus happen as a result of cohesion or adhesion?

Answer 22

Adhesion

Question 23

Describe how tension is created during transpiration.

Answer 23

• Water transpires/evaporates from stomata
• This reduces water potential across the cells in the leaf
• Water is drawn out from the xylem
• This creates tension (negative pressure)

Question 24

Would a cross section of a stem be described as transverse or longitudinal?

Answer 24

Transverse

Question 25

When setting up a potometer, what is vaseline used for?

Answer 25

To seal any gaps, to make sure it is air tight.

Question 26

Briefly describe how a potometer can be used to measure the rate of transpiration.

Answer 26

- Record the starting position of the bubble - Leave for 5 minutes - Record the end position of the bubble - Calculate the distance travelled - Calculate the rate of movement per minute

Question 27

Why is a potometer not the best model for transpiration? What is assumed?

Answer 27

This model assumes that all the water that is absorbed through the roots is lost through transpiration. In reality, some of the water is used in photosynthesis or for turgidity.

Question 28

When using a potometer, how can you return the air bubble to the start of the capillary tube?

Answer 28

Open the tap

Question 29

List the precautions you should take when using a potometer to ensure you obtain reliable measurements.

Answer 29

- Use vaseline to seal joints (to keep it airtight) - Cut shoot underwater - Cut shoot at a slant - Dry off leaves - Insert plant into apparatus underwater - Ensure no air bubbles are present - Shut tap - Note where bubble is at the start

Question 30

What are apoplasts?

Answer 30

A series of intercellular spaces which mostly run through the cell wall.

Question 31

Water moving through the apoplastic pathway is an example of which type of cell transport?

Answer 31

Diffusion (This is NOT osmosis, as there is no movement across a partially permeable membrane.)

Question 32

The Casparian strip is made up of a waxy substance called...

Answer 32

Suberin

Question 33

Water entering the symplast is an example of which type of cell transport?

Answer 33

Osmosis

Question 34

Does most water travel more quickly through the apoplastic or symplastic pathway?

Answer 34

Apoplastic pathway, as water does not have to pass through a partially permeable membrane.

Question 35

Name pathway 2.

Answer 35

Symplastic

Question 36

Name pathway 3.

Answer 36

Apoplastic