Water Transport

Question 1

What are the advantages of living on land (2)

Answer 1

more light
oxygen and carbon dioxide more plentiful

Question 2

what are the challenges of living on land (4)

Answer 2

overcoming gravity (early plants lacked lignin)
water less plentiful (maintain moisture)
water/nutrients at different locations than gases
dispersal of gametes

Question 3

what are the five adaptations to living on land

Answer 3

1. maintaining moisture
2. reproduction an dispersal
3. obtaining resources from two locations
4. support body against gravity
5. protection against stresses (abiotic and biotic)

Question 4

how did plants adapt to maintain moisture on land

Answer 4

water transport systems (soil —> leaves)
cuticle/stomata to avoid/regulate water loss
pollen/seeds resistant to desiccation

Question 5

how did plants adapt to reproduce on land

Answer 5

animal pollination, fruits, more targeted dispersal

Question 6

how did plants adapt to obtain resources from two locations

Answer 6

larger leaves increase photosynthesis, larger plants, shoot and root system, transport systems (xylem and phloem)

Question 7

how did plants adapt to gravity

Answer 7

thicker cell walls and lignin

Question 8

how did plants adapt to protect against stresses

Answer 8

secondary metabolites

Question 9

what came first? increased photosynthetic surfaces or increased water transport infrastructure

Answer 9

water transport

Question 10

why did the first plant grow upwards

Answer 10

because of new lignified xylem tissue

Question 11

why do mosses not grow tall like trees

Answer 11

they lack vascular tissues and lignin

Question 12

what is the function of primary growth, how does this occur

Answer 12

to grow tall, growth at the tip

Question 13

what is the function of secondary growth, how is this done?

Answer 13

to grow thicker, growth from the center

Question 14

what is the secondary xylem

Answer 14

wood

Question 15

how is secondary growth arranged going from centre to outside

Answer 15

primary xylem, secondary xylem, cambium/lateral meristem, secondary phloem, primary phloem

Question 16

what are the two lateral meristems

Answer 16

vascular and cork cambium

Question 17

what is the vascular cambium, which direction is growth

Answer 17

separates xylem and phloem, growth is inward and outward

Question 18

what is the cork cambium and direction of secondary growth

Answer 18

secondary dermal tissue on the outside, outwards

Question 19

what is bark

Answer 19

secondary phloem and cork

Question 20

what is the vascular cambium

Answer 20

stem cells

Question 21

how does leaves and wood help transport water

Answer 21

leaves evaporate water and help pull up xylem sap
wood stabilizes stem and forms new xylem each year

Question 22

what are the three pathways water and nutrients move

Answer 22

apoplastic, symplastic, transmembrane

Question 23

what is the apoplastic route

Answer 23

easy, through the cell wall

Question 24

what is the symplastic pathway

Answer 24

transport through the cytosol via plasmodesmata

Question 25

what is the transmembrane route

Answer 25

crossing plasma membrane, not as easy

Question 26

what is an example of active transport of solute

Answer 26

pH gradient via proton pump (pumps H+ out of cell)

Question 27

what is an example of co-transport of neutral solutes with protons

Answer 27

sucrose with the pH gradient (H+), occurs in the phloem

Question 28

what is an example of co-transport of ions/nitrates with protons

Answer 28

H+ gradient with nitrate, mineral uptake into roots

Question 29

what are aquaporins

Answer 29

bidirectional channel proteins that allow only water molecules to pass

Question 30

why do are aquaporins needed

Answer 30

because the plasma membrane in made of fats making it water repellent, however not water impermeable

Question 31

what is water potential

Answer 31

potential energy of water under given conditions compared to pure water under reference conditions

Question 32

what is driven by water potential

Answer 32

direction of water flow (high potential to low potential)

Question 33

what are two factors that affect water potential

Answer 33

pressure and solute concentration

Question 34

what is an example of pressure potential

Answer 34

turgor pressure = pressure of plasma membrane against cell wall, and wall against protoplast

Question 35

what occurs when the surroundings have lower water potential

Answer 35

plasmolysis

Question 36

what occurs when the cell has lower water potential than pure water

Answer 36

turgid

Question 37

where does water enter roots

Answer 37

via root hairs

Question 38

what transport occurs at the casparian strip

Answer 38

symplastic

Question 39

what transport occurs at the tracheary element loading

Answer 39

transmembrane

Question 40

what transport occurs within the xylem

Answer 40

apoplastic

Question 41

where does water evaporate

Answer 41

at leafs surface

Question 42

what is water and mineral transport in the xylem driven by

Answer 42

transpiration in leaves

Question 43

what does transpiration in leaves involve and create

Answer 43

water vapour diffuses from moist air spaces in the lead to drier air outside via stomata creating a steep water vapour gradient

Question 44

what are the three general steps in water transport

Answer 44

water uptake from soil in roots, cohesion and adhesion in the xylem, transpiration in leaves

Question 45

what is cohesion and adhesion

Answer 45

cohesion = water molecules stick to each other adhesion = water molecules stick to the walls of cells

Question 46

what type of bond is involved in cohesion/adhesion

Answer 46

hydrogen

Question 47

what happens if the hydrogen bonds break?

Answer 47

cavitation

Question 48

what is bulk flow driven by

Answer 48

evaporation: difference in pressure potential

Question 49

do cells need to be alive to perform bulk water flow?

Answer 49

no

Question 50

how much ATP/energy is used for the bulk flow of water?

Answer 50

none ---> flow is not driven by biochemical processes but by the physical force of evaporation

Question 51

what is transpiration

Answer 51

water loss by aerial organs

Question 52

what is the function of the cuticle

Answer 52

prevents water loss at surface

Question 53

where does water loss occur

Answer 53

through the stomata

Question 54

how is water loss regulated

Answer 54

by stomatal density and pore opening/closing

Question 55

how do stoma open

Answer 55

K+ ions pumped into cell, water follows K+ making guard cells turgid

Question 56

how do stoma close

Answer 56

K+ ions pumped out, water follows, guard cell lose water and become flaccid

Question 57

when are stomata usually open or closed and why

Answer 57

day = open, night = closed to balance CO2 uptake and water loss ---> driven by light/CO2 status/circadian rhythm

Question 58

what environmental stresses can stomata respond to and how

Answer 58

heat/drought/wind = closure of stomata = hormone driven via abscidic acid