ADAPTATIONS FOR TRANSPORT IN PLANTS

Question 1

2 functions of xylem

Answer 1

• transport water and mineral ions
• mechanical support

Question 2

What is xylem made from

Answer 2

Lignin

Question 3

What do the breaking down of cell wall in xylems form

Answer 3

Hollow tubes

Question 4

What do non lignified pits do

Answer 4

Allow water and mineral ions to move out xylem

Question 5

What does the xylem parenchyma do

Answer 5

Store food

Question 6

What are cell walls like in phloem

Answer 6

Partially broken down

Question 7

What do partially broken down cell walls in phloem form

Answer 7

Sieve tubes element

Question 8

2 features of companion cells

Answer 8

Keep phloem alive
Involved in translocation

Question 10

What are gaps in cell wall called

Answer 10

Plasmodesmata

Question 11

Define apoplast pathway

Answer 11

Water moves Between cell walls

Question 12

Define symplast pathway

Answer 12

Water moves through cytoplasm and plasmodesmata by diffusion

Question 13

What is casperian strip made of

Answer 13

Suberin

Question 14

What does casperian strip cause

Answer 14

Water to move from apoplast pathway to symplast pathway across plasma membrane

Question 15

Describe how water moves into xylem

Answer 15

1. Ions move into epidermis by active transport lowering water potential in xylem and increasing water potential in epidermis
2. Water moves into xylem by osmosis lowering water potential gradient
3. Root pressure is generated so water is pushed up xylem

Question 16

Define transpiration

Answer 16

Loss of water vapour by evaporation through stomata

Question 17

4 factors affecting rate of transportation

Answer 17

Temperature
Humidity
Light intensity
Air speed

Question 18

How does temperature affect rate of transpiration

Answer 18

Increase = increase rate
More kinetic energy

Question 19

How does humidity affect rate of transpiration

Answer 19

Increase = decrease rate
Steep water vapour concentration gradient

Question 20

How does air speed affect rate of transpiration

Answer 20

Increase = increase
Air blows water vapour

Question 21

How does light intensity affect rate of transpiration

Answer 21

Increase = increase
More stomata open
Increase photosynthesis and carbon dioxide

Question 22

What does potometer do

Answer 22

Measure water uptake by plant and estimates transpiration rate

Question 23

What are mesophyte

Answer 23

Plants adapted to living in either wet or dry environments

Question 24

What are hydrophytes

Answer 24

Plants that are adapted to living in aquatic environments

Question 25

What are xerophytes

Answer 25

Plants that are adapted to living in little liquid water environments

Question 26

Describe structure of mesophytes

Answer 26

- shed leaves before winter = not lose water by transpiration if water is scarce - aerial parts of non woody plants die in winter = not exposed to cold or frost - Dormant seeds = low metabolic rate so no water required

Question 27

Describe structure of xerophytes

Answer 27

- sunken stomata = trap humid air causing lower water potential so less diffusion - interlocking hairs = trap water vapour decreasing water potency gradient - waterproof cuticle = prevent water loss - rolled leaves = reduce transpiration

Question 28

Describe structure of hydrophytes

Answer 28

- stomata on upper surface - no cuticle = no need to prevent water loss - large air spaces in stem and leaves = buoyancy from co2 and oxygen resoviour - xylem poorly developed = little need for transpiration

Question 29

Describe process of translocation

Answer 29

- protons pumped out of companion cell by active transport through proton pump - protons diffuse back inside CC with sucrose via co transporters - sucrose diffuse from CC into sieve tube elements through plasmodesmata lowering water potential in STE - water moves back into sieve tubes via osmosis which generates turgor pressure for mass flow

Question 30

Describe process of mass flow

Answer 30

- assimilates flow from source to sink down pressure gradient - sucrose diffuse from phloem into sinks - survive moved into other cells / converted into other forms and maintains concentration gradient between cells and phloem - loss if assimilates increase water potential of sieve tube elements so water moves out into cells by osmosis or enters xylems transpiration stream