Topic 6 - transport in plants

Question 1

What tissue in a plant transports sugars from photosynthesis?

Answer 1

Phloem tissue

Question 2

Which tissue in a plant transports water and mineral ions?

Answer 2

Xylem tissue

Question 3

What type of flow do mammals and plants use?

Answer 3

Mass flow

Question 4

What are xylem and phloem collectively known as?

Answer 4

Vascular tissue

Question 5

What is the difference in a plants mass flow in comparison to a mammals mass flow?

Answer 5

Plants don’t have a pump, the heart

Question 6

Where are xylem and phloem found in a plant?

Answer 6

In the vascular bundle in the stem and the central stele in the root

Question 7

What makes xylem tissue so strong?

Answer 7

There’s lignin in the cellulose fibres making it much stronger so can withstand high tension

Question 8

Why do plants need xylem vessels to transport water?

Answer 8

Because otherwise the water would mix with the cytoplasm (plants don’t have a circulatory system like mammals)

Question 9

What makes a xylem cell wall impermeable?

Answer 9

The lignin that develops inbetween cellulose fibres

Question 10

What are pits and why do plants need them?

Answer 10

Parts of a xylem vessel cell wall with no lignin so water can filtrate through, they are needed to allow cross flow (water to travel between xylem vessels)

Question 11

What helps a plant to withstand drops in pressure/ stop collapse?

Answer 11

The different thickness of lignin for example rings or blocks of thick lignin

Question 12

Why isn’t there thick lignin around all the xylem vessels anyway?

Answer 12

Because the stem still needs to be flexible to withstand different pressures

Question 13

What two properties of water allow water to move through the xylem in continuous streams?

Answer 13

Adhesion (sticking to wall of xylem) 
And cohesion (water molecules sticking together)

Question 14

What are the 3 ways of water transport through a plant?

Answer 14

1. ) mass flow
2. ) diffusion
3. ) osmosis

Question 15

What is mass flow?

Answer 15

The movement of water through the apoplast pathway

Question 16

What is the apoplast pathway?

Answer 16

Movement of water in a pathway which doesn’t go through any living contents of the cell or membranes including spaces between cellulose fibres and xylem vessels

Question 17

How do water molecules diffuse in a plant?

Answer 17

They go via the symplast pathway which is through the plasmodesmata. Water travels through the cytoplasm of a cell however in the cytoplasm there are many organelles and other molecules which slow diffusion

Question 18

How would water travel through a plant via osmosis?

Answer 18

From vacuole to vacuole, from a high to low concentration.

Sometimes known as vacuolar pathway

Question 19

What are the 3 ways of water transport through a plant?

Answer 19

1. ) mass flow
2. ) diffusion
3. ) osmosis

Question 20

What is mass flow?

Answer 20

The movement of water through the apoplast pathway

Question 21

What is the apoplast pathway?

Answer 21

Movement of water in a pathway which doesn’t go through any living contents of the cell or membranes including spaces between cellulose fibres and xylem vessels

Question 22

How do water molecules diffuse in a plant?

Answer 22

They go via the symplast pathway which is through the plasmodesmata. Water travels through the cytoplasm of a cell however in the cytoplasm there are many organelles and other molecules which slow diffusion

Question 23

How would water travel through a plant via osmosis?

Answer 23

From vacuole to vacuole, from a high to low concentration.

Sometimes known as vacuolar pathway

Question 24

How does water in a xylem vessel have great tensile strength?

Answer 24

Because of the load of hydrogen bonds in the xylem vessel it means there’s a great amount of cohesion therefore the water has great tensile strength

Question 25

What 3 things allow water to move up a xylem water column (according to the cohesion tension model)?

Answer 25

1. )The transpiration on aerial parts of the plant means there’s pressure on the water column causing a continuous column of water to be pulled up from the root
2. ) cohesion - tensile strength
3. ) adhesion

Question 26

Why is it important for a column of water being drawn up a xylem vessel to have great tensile strength?

Answer 26

So it doesn’t break on its way up

So it can go upwards at a great height without breaking

Question 27

What affects the rate of water movement in a plant?

Answer 27

1. ) temperature. The higher temp= more kinetic energy = more evaporation
2. ) humidity. The more humid = lower concentration gradient = slower diffusion
3. ) air movements. The slower wind = more water molecules around the surface of leaf = Lower concentration gradient = slower diffusion
4. ) light. Darker = guard cells flaccid= closed stomata = less diffusion of water vapour