2.3 B adaptations for transport in plants

Question 1

what is the vascular tissue that transports materials around plant?

Answer 1

xylem and phloem

Question 2

what are the two main cell types in the xylem?

Answer 2

vessels and tracheids

Question 3

what do tracheids occur in? what do they not occur in? what does this mean?

Answer 3

ferns, conifers, flowering plants

not in mosses - have a no water-conducting tissue therefore poorer at transporting water - cannot grow as tall

Question 4

what do vessels only occur in?

Answer 4

angiosprems

Question 5

what are two functions of the xylem?

Answer 5

1. transport of water and dissolved minerals

2. providing mechanical strength and support

Question 6

why in the xylem is the greatest uptake of water in the root hair zone?

Answer 6

surface area is increased by the presence of root hairs

uptake enhanced by their thin cell walls

Question 7

why does water pass into the root hair cell by osmosis down a water potential gradient?

Answer 7

soil has high water potential and vacuole and cytoplasm contain solution that has a lower more negative water potential

Question 8

what are the three pathways water can take to be distributed around the plant?

Answer 8

1. apoplast
2. symplast
3. vacuolar

Question 9

what is meant by the apoplast pathway?

Answer 9

water moves in cell walls. celluose fibres in cell wall are separated by spaces so water can move through

Question 10

what is meant by the symplast pathway?

Answer 10

water moves cytoplasm and plasmodesmata

Question 11

what is menat by vacuolar pathway?

Answer 11

water moves from vacuole to vacuole

Question 12

define what is menat by endodermis

Answer 12

single layer of cells around the vascular tissue around the root - each cell has a impermeable waterproof barrier in its cell wall

Question 13

what is meant by the casparian strip?

Answer 13

blocks the movement of water in the apoplast driving it to the cytoplasm

Question 14

water moves from the root endodermis into the xylem by…?

Answer 14

osmosis

Question 15

state 2 ways we achieve a more negative water potential of the xylem than the endodermal cells

Answer 15

1. water potential is raised by water being driven in by the casparian strip
2. water potential of xylem is decreased by active transport of mineral salts

Question 16

how are minerals absorbed into the cytoplasm?

Answer 16

active transport - against a concentration gradient

Question 17

water moves from the soil through the plant into the air. what are the three main mechanisms in which it does this?

Answer 17

1. transpiration pull
2. capillartiy
3. root pressure

Question 18

what is meant by the mechanism transpiration pull?

Answer 18

water molecules show cohesion which produces tension in water column. cohesion-tension theory - water movement up xylem by combining adhesion and tension of water column

Question 19

what is meant by the mechanism capillarity?

Answer 19

movement of water up narrow tubes - only over short distances

Question 20

what is meant by the mechanism root pressure?

Answer 20

consequence of osmotic movement of water into xylem pushing water already there further up

Question 21

in the transpiration stream, water is drawn upwards by what 2 ways? see pic page 206

Answer 21

1. cohesive forces between water molecules

2. adhesive forces and hydrophilic lining of xylem vessels

Question 22

define transpiration.

Answer 22

evaporation of water vapour from the leaves out through the stomata into the atmosphere

Question 23

what 4 factors affect the rate of transpiration?

Answer 23

1. temperture
2. humidity
3. air movement
4. light intensity

Question 24

how does a temperature increase effect the rate of transpiration?

Answer 24

increase in temp lowers the water potential therefore increases kinetic energy of molecules - increases rate of evaporation

Question 25

why does the transpiration rate decrease when the humidity in the air is higher?

Answer 25

water potential gradient between leaf and atmosphere so when stomata open water diffuses out down potential gradient

Question 26

how does increased wind speeds increase transpiration?

Answer 26

because it removes the concentric shells of water vapour from around the stomata

Question 27

how does a higher light intensity increase the rate of transpiration?

Answer 27

stomata open wider more water lost - tend to be more open in the day

Question 28

define what is meant by translocation?

Answer 28

the active movement of soluble products of photosynthesis such as amino acids through the phloem

Question 29

what is phloem made up of?

Answer 29

sieve tubes and companion cells

Question 30

what 2 experiments have been done to prove that organic substances are translocated through the phloem?

Answer 30

1. ringing experiments

2. radioactive tracers and autoradiography

Question 31

what is meant by radioactive tracers and autoradiography?

Answer 31

stem section placed on photographic film which is exposed to radiation source. position of exposure concedes with position of phloem indicating phloem translocates sucrose