Plant Mass Transport

Question 1

What does the xylem transport

Answer 1

Water and mineral ions

Question 2

What do the phloem vessels transport

Answer 2

Sugars

Question 3

What are xylem tubes made from

Answer 3

Dead cells (vessel elements)

Question 4

Give an adaption of the xylem vessel

Answer 4

No end walls

= uninterrupted tube = no resistance to water

Question 5

Explain the cohesion-tension theory of water

Answer 5

1. Water evaporates at the leaf
2. Creates tension pulling more water up
3. Water molecules are cohesive. So the whole colum of water is pulled up
4. Water Exeter’s stem by roots

Question 6

What is transportation.

Answer 6

The evaporation of water from the stomata Down the Conc grad

Question 7

How does light affect transportation rate

Answer 7

High light intensity = increased rate

Stoma open for photosynthesis

Question 8

How does temp affect transpiration rate

Answer 8

High temp = high rate
Water molecules have more energy
Evaporate faster
Increases concentration grad

Question 9

How does humidity affect transpiration rate

Answer 9

High humidity = low rate
More water molecules surrounding stoma
Low conc grad

Question 10

How does wind affect transpiration rate

Answer 10

High wind = high rate
Wind blows water molecules away from leaf
Maintains conc grad

Question 11

What are the 2 structures in the phloem

Answer 11

Sieve tube elements

Companion cell

Question 12

Adaption of serve tube elements

Answer 12

No nucleus and few organelles = less resistance to transported materials

Question 13

What is the function of companion cells

Answer 13

Carry out living function s of rice tube elements

Eg. Respiration for active transport

Question 14

What is the structure between sieve tube elements

Answer 14

Sieve Plates

Question 15

Define translocation

Answer 15

Movement of solutes to where they are needed

Question 16

Is translocation passive or needs energy

Answer 16

Needs energy

Question 17

Where does translocation move molecules to

Answer 17

Source to sink

Question 18

How is a conc grad Maintained for translocation

Answer 18

Enzymes break down solutes at the sink into something else

Question 19

Explain the mass flow hypothesis

Answer 19

Source:
1. Active transport moves solutes from companion cells of sieve tubes
2. Lower water potential in sieve tube 
3. Water whether sieve tube 
4. Increases p 
Sink:
5.  Solutes removed from sieve tubes 
6. Increases water potential 
7. Water leaves 
8. Lowers pressure 
Overall:
Pressure gradient from source to sink

Question 20

Give 4 pieces of Evidence for mass flow

Answer 20

1. If a ring of bark is removed (including phloem Not xylem) A bulge forms above the ring, and has a higher conc than the fluid below = shows downward flow
2. Radioactive tracers can be tracked eg. C14
3. Sal flows out faster at the leaves than at the roots = pressure gradient
4. If a metabolic inhibitor is used = translocation stops = uses active transport

Question 21

Give 2 pieces of evidence against mass flow hypothesis

Answer 21

1. Sugar travels to many different sinks not just the one with the higher water potential.b
2. Sieve plates would create a barrier so a lot of p would be needed

Question 22

How do you use radioactive tracers to show mass flow

Answer 22

1. Supply plant with C14
2. Taken in by photosynthesis and used to make sugars
3. Miovement of sugars tracked by autoradiography
4. Kill plant by liquid N
5. Place on photographic film
6. Radioactive substances turn black

Question 23

What do potomètres measure

Answer 23

Water uptake by a plant

Question 24

What is assumed when using a potomètre

Answer 24

The water uptake by roots is directly proportional to water loss by the leaves

Question 25

Method of using a potomètres to measure transpiration;

Answer 25

1. Cut shoot underwater at a slant
2. Assemble potomètre under water and put shoot in
3. Remove potomètre from water but keep end of capillary tube submerged
4. Dry leaves and wait 10 mins for plant to acclimatise
5. Shut tap
6. Remove end of capillary tube until 1 air bubble forms
7. Record starting pos of air bubble
8. Start stop watch and record distance every 10 secs

Question 26

Why is the root cut at a slang using a potomètre

Answer 26

Increases sa for water uptake

Question 27

Why cut shoot under water when using a potomètre

Answer 27

Prevents air from entering the xylem