Mass Transport in Plants - Xylem

Question 1

angiosperm

Answer 1

flowering plant

Question 2

xylem

Answer 2

transports water and mineral ion

Question 3

phloem

Answer 3

transports sucrose and a.a. (PS products) in water as sap

Question 4

fibre in vascular bundle

Answer 4

provides mechanical support

Question 5

parenchyma cells

Answer 5

packing cells

Question 6

which cells in the vascular bundle are living?

Answer 6

parenchyma cells

Question 7

which cells are tapered in the vascular bundle?

Answer 7

tracheids

Question 8

why are xylem vessels dead?

Answer 8

lignified walls are impermeable stopping exchange so cell dies and it loses its organelles

Question 9

function of lignin rings

Answer 9

strengthens cell wall, prevnting xylem collapsing as water moves up

Question 10

transpiration

Answer 10

the evaporation of water out the mesophyll cells to become water vapour in the air spaces, and the subsequent diffusion of the water vapour out the stomata

Question 11

percentage of water taken up that is transpired

Answer 11

99%

Question 12

what happens to the water that isn’t transpired?

Answer 12

it is used for photosynthesis and maintaining turgid pressure

Question 13

by what process does water vapour pass out of the stomata?

Answer 13

diffusion

Question 14

how does water move across the leaf?

Answer 14

evaporation of water decreases the WP so cells pull water from neibouring cells

Question 15

why is so much water transpired?

Answer 15

• acts as a coolant
• mineral ions dissolve in water so more water brings more ions through roots
• need to keep stomata open for PS and RS

Question 16

desribe the movement of water through the xykem by cohesion tension (5)

Answer 16

1. water transpires out the leaves
2. decreases water potential in leaves,
3. creating tension on water column
4. water pulled up in a single column due to cohesion between molecules as a result of hydrogen bonds
5. water sticks to side of xylem because of adhesive properties

Question 17

name the 6 parts of a stem

Answer 17

1. epidermis
2. cortex
3. phloem
4. cambium
5. xylem
6. pith

Question 18

name the 8 parts of a root

Answer 18

1. epidermis
2. exodermis
3. cortex
4. endodermis
5. pericycle
6. phloem
7. cambium
8. xylem

Question 19

describe and explain the location of the vascular bundle in a stem

Answer 19

• located on periphery of stem
• stem arial structure so subject to bending strains imposed by wind
• require support in peripheries to support from all directions

Question 20

describe and explain the location of the vascular bundle in the root

Answer 20

• located in the centre
• root below ground so subject to pulling force of gravity
• support needed in central column to support pull in single direction

Question 21

root pressure theory

Answer 21

• mineral ions actively transported into root
• decreases WP
• water drawn up by osmosis
• mire mineral ions therefore more water taken up increasing hydrostatic pressure in root, pushing wtaer up stem

Question 22

capillary action theory

Answer 22

• ability of liquid to flow through a narrow spae, usually against gravity
• occurs bc of intermolecular attraction forces

Question 23

cohesion (+ in wtaer movement)

Answer 23

attraction between the same molecules (water-water)

Question 24

adhesion (+ in water movement)

Answer 24

attraction between different molecules (water-lignin)

Question 25

3 features of a root hair cell to increase uptake

Answer 25

• Large SA so many mitochondria
• many carrier proteins
• thin cell walls so don’t interrupt water flow

Question 26

type of uptake of mineral ions

Answer 26

• partly passsive - facilitated diffusion
• mostly active - AT

Question 27

evidence of active trasnport of mineral ions

Answer 27

• ion concentration of root much greater than in soil - against gradient, needing energy - AT
• adding RS inhibitor decreases uptake - requires ATP therefore AT

Question 28

4 steps of movement in a potometer

Answer 28

1. wtaer transpires
2. water taken up by shoot
3. water moves along capillary tube
4. air bubble moves

Question 29

what is the reservoir used for in a potometer?

Answer 29

used to return bubble to start for repetitions

Question 30

8 steps of setting up a potometer

Answer 30

1. cut shoot underwater
2. assemble potometer and insert shoot underwater
3. remove from water, keeping end of tube in beaker
4. ensure all joints airtight, e.g. used vaseline
5. dry leaves
6. remove end of tube to create air bubble
7. record starting position of air bubble
8. record distance and time moved of air bubble

Question 31

rate of water uptake formula

Answer 31

speed of air bubble movement x cross-sectional area of tube

Question 32

4 factors affecting transpiration rate

Answer 32

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

Question 33

explain how increased light intensity affects transpiration rate

Answer 33

• increases transpiration rate
• increased light intensity stimulates stomatal opening for gas exchange for PS
• increased number of stamata open increases SA for diffusion of water vapour

Question 34

explain how increased temperature affecs transpiration rate

Answer 34

• increases transpiration rate
• increases evaporation out mesophyll cells
• air spaces in leaf become more saturated with water so increase diffusion gradient to outside leaf

Question 35

explain how increased humidity affects transpiration rate

Answer 35

• decreases transpiration rate
• as water oves out, remains in air raound stomata so air saturated
• reduces diffusion gradient fom inside to outside leaf

Question 36

explain how increased air movement affects trasnpiration rate

Answer 36

• increases
• saturated air moves away, increasing diffusion gradient