Transport in plants 4.4

Question 1

Why does the xylem contain pits?

Answer 1

To allow water to move sideways between the vessels

Question 2

What tissue is the xylem made up of?

Answer 2

Dead tissues

Question 3

What is the xylem thickened with?

Answer 3

Lignin

Question 4

How is lignin deposited?

Answer 4

Spiral patterns to maintain flexibility

Question 5

What is translocation?

Answer 5

The movement of nutrients to storage organs

Question 6

What cells does the phloem consist of?

Answer 6

Companion cells
Sieve tubes

Question 7

What is the plasmodesmata?

Answer 7

Gaps between cell walls allowing flow of substances between cells

Question 8

How does water move through the symplast pathway?

Answer 8

Water moves through the cytoplasm via the plasmodesmata

Question 9

How does water move through the apoplastic pathway

Answer 9

Water moves through cell walls and intercellular spaces which are permeable

Question 10

Through what cells does water move into the plant?

Answer 10

Root hair cells

Question 11

How is the column of water maintained?

Answer 11

Through cohesion and adhesion

Question 12

What is cohesion?

Answer 12

Attraction between like molecules, water forming hydrogen bonds with other molecules of water

Question 13

What is adhesion?

Answer 13

Attraction between unlike molecules

Question 14

What causes hydrostatic pressure in the xylem?

Answer 14

Evaporation

Question 15

What does hydrostatic pressure in the xylem cause?

Answer 15

The tension moves the whole column upwards due to cohesion, this is the cohesion-tension model

Question 16

What does sucrose move from-to?

Answer 16

Moves from the source (produces more sugar than required) to the sinks (eg, root and shoot)

Question 17

How does light intensity affect transpiration?

Answer 17

Increases the number of stomata that are open for gas exchange

Question 18

How does air movement affect transpiration?

Answer 18

Removes still air from around the leaf and increases the concentration gradient, increasing diffusion

Question 19

What is the mass flow hypothesis?

Answer 19

Explains the movement of assimilates in the phloem

Question 20

What is one bit of evidence to support the mass flow hypothesis?

Answer 20

-You can use radioactive isotopes to mark glucose and trace sucrose through the phloem

Question 21

What are two weaknesses of the mass flow hypothesis?

Answer 21

-Doesn’t explain why there can be bidirectional movement in the sieve tube
-Doesn’t explain different speeds of movement in the phloem