Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

bio component 3 > plant gas exchange and transport > Flashcards

plant gas exchange and transport Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
1
Q

what do plants only do in the dark?

A

respire (no photosynthesis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are the internal structures in a leaf (in order from outside to furthest inside)?

A

waxy cuticle
upper epidermis
palisade mesophyll layer
spongy mesophyll layer
xylem and phloem
bundle sheath cells
lower epidermis
guard cell
stoma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what kind of gas exchange do plants use?

A

diffusion
thin, flat, large surface area
large air spaces for circulation of gases
stomatal pores can open

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

how do gases diffuse into leaf?

A

gases diffuse through stoma down conc gradient
gases diffuse through intracellular spaces between mesophyll cells
gases dissolve in film of water covering cells and in cellulose cell walls
gases then diffuses into cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what gases come in and out in daylight?

A

CO2 in
O2 out

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what gases come in and out in darkness?

A

O2 in
CO2 out

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are the leaf adaptions for light harvesting?

A

large SA to capture as much light as possible
leaves can move to position themselves into more light
cuticle and epidermis are transparent so light can get to mesophyll cells
leaves are thin so light can get to lower layers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is the waxy cuticle?

A

secreted by epidermal cells
waterproof
reduces warer loss through epidermis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what are features of the palisade mesophyll layer?

A

elongated
densely packed with chloroplasts
chloroplasts can move in cells to collect more light and get away from strong light to avoid damage
small air spaces between cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what are features of epidermal cells?

A

transparent
no chloroplasts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what does the stomata do?

A

reduces gas exchange and water loss when closed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what are guard cells?

A

cells in epidermis which can shape to form stoma for gas exchange

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is guard cell tugor?

A

guard cell changes shape to open/close stomata
when water flows in guard cell, cells becomes turgid and curve away from each other (inner wall is thicker and less elastic than outer wall)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how do guard cells work (in DARKNESS)?

A

K+ ions diffuse out of guard cells down conc gradient
malate is converted to starch
both of the above raise the water potential inside the cells
water flows out of cells down water potential gradient
tugor of guard cells changes shape
stoma closes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

how do guard cells work (in LIGHT)?

A

K+ ions move into guard cells by active transport
starch is converted to malate
water flows into cells down water potential gradient
tugor increases
guard cell changes shape
stoma opens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

where do guard cells get their energy from for its processes?

A

chloroplasts inside the cell that provide ATP for active transport

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what are xerophytes?

A

plants adapted to survive in very dry conditions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

how are xerophytes adapted to their conditions?

A

close stomata during day and open at night to reduce water loss
leaves are needles/spines to reduce SA for water loss
curled leaves, sunken stomata, hairy leaves all create damp areas to decrease water potential gradient
shallow roots covering large SA
thick cuticle
low stomata density

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what does the xylem do?

A

transports water and mineral salts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what does the phloem do?

A

transports sugars and amino acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what are the 2 main types of water conducting tissues?

A

tracheids
vessels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what are water conducting tissues?

A

continuous tubes
lack cytoplasm
column of water travels up in one direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

why are dead cells used in xylem?

A

lignin in their cellulose cell walls makes them impermeable
lignin is deposited as rings/spirals which provides mechanical strength (prevents collapse of xylem)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what are features of vessels?

A

main conducting tube
wide cells with reduced or absent end

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what are features of tracheids?

A

slightly narrower than vessels
perforated end walls
water flow is more obstructed than in vessels
provide more support than vessel cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what is the path of water up the xylem?

A

water uptake by roots
water movement through roots
water movement from roots to leaves

27
Q

how are roots adapted for the uptake of water?

A

large SA for water to enter by osmosis
cellulose cell wall freely permeable to water
larger number of mitochondria to provide ATP for active transport

28
Q

what are features of the structure of a root hair cell?

A

cortex cells
endodermis
phloem and xylem

29
Q

how does a root hair cell take in water?

A

mineral ions are actively transported from soil into root hair cell
root cell now has a low water potential
water moves into root hair cell by osmosis then into the first cortex cell

30
Q

what are the two pathways that water can take across the root?

A

symplastic pathway
apoplastic pathway

31
Q

what is the symplastic pathway?

A

movement of water by cytoplasm and plasmodesmata

32
Q

what is the apoplastic pathway?

A

movement along cell wall or between free spaces of cells

33
Q

what happens at the endodermis of the root?

A

all water is forced into symplast route by the casparian strip

34
Q

what is the casparian strip?

A

waterproof layer in cell walls

35
Q

how does water move into the xylem after it has crossed the root?

A

ions actively transported into xylem
water potential is less in xylem than endodermal cells
water moves into xylem by osmosis

36
Q

how does water move from roots to leaves?

A

passive process
down water potential gradient

37
Q

what are the 3 mechanisms of water movement?

A
  • some initial movement due to active transport of mineral ions across endodermis of root which creates root pressure
  • capillary action, movement of liquid caused by attraction of liquid molecules to solid cellulose molecules in cell wall
  • cohesion/tension theory
    cohesion = polar water molecules create a column
    adhesion = between water and hydrophilic lining of cell wall
38
Q

what is transpiration?

A

evaporation of water vapour from leaves through stomata reduces pressure at top of xylem so creates transpiration stream
continuous removal of water molecules from top of xylem results in tension that pulls water up from roots

39
Q

what are the factors affecting transpiration?

A

light intensity
air movement
temperature
humidity

40
Q

how does light intensity affect transpiration?

A

affects degree of opening and closing stomata
more light means more stomata open
so rate of T increases

41
Q

how does air movement affect transpiration?

A

maintains gradient by blowing away humid air which accumulates around stomata

42
Q

how does temperature affect transpiration?

A

warm air has more kinetic energy so transpiration rate increases as H2O diffuses away from leaf quicker

43
Q

how does humidity affect transpiration?

A

reduces rate of transpiration as no steep concentration gradient

44
Q

what is the transpiration practical steps?

A

measure using podometer
cut leafy shoot at an angle under water
air bubble
measure time and distance

45
Q

what are hydrophytes?

A

plants adapted to live in fresh water

46
Q

how are hydrophytes adapted to live in fresh water?

A

floating leaves due to thin, flat leaves with large air spaces
thin or absent waxy cuticle (as no need to reduce water loss)
stomata located on upper surface of leaf
reduced root system and veins in leaves

47
Q

what are mesophytes?

A

plants that live with adequate water

48
Q

how are mesophytes adapted to their environment?

A

close stomata at night to reduce water loss
shed leaves in unfavourable conditions
underground organs and dormant seeds survive the winter

49
Q

where is phloem in a stem?

A

the outside half of the circles

50
Q

where is phloem in a root?

A

not the cross
the circles in between the cross

51
Q

what are the 2 main cell types in phloem?

A

sieve tubes
companion cells

52
Q

what are the properties of sieve tubes?

A

cell walls where they join have sieve plates
living cells
no nucleus
form main conducting tube for transport of soluble organic materials made by photosynthesis

53
Q

what are the properties of companion cells?

A

next to each sieve element
life support units
dense cytoplasm
many mitochondria so metabolically active
connected to sieve by plasmodesmata

54
Q

what are some other cells in phloem?

A

phloem fibres (support)
parenchyma (packing tissues)

55
Q

what is translocation?

A

products of photosynthesis are transported away from source to areas of plant where they are used for growth or storage

56
Q

what is the mass flow theory?

A

original theory was that translocation was thought to be a passive process
(is now thought to be active)

57
Q

what is the evidence against the mass flow theory?

A

function of sieve plates?
companion cells contain many mitochondria
sucrose and amino acids move at different rates and directions
phloem has a high rate of O2 consumption

58
Q

what is the new theory for translocation?

A

active process
cytoplasmic streaming could be responsible for bi-directional movement in sieve tubes

59
Q

how does cytoplasmic streaming work?

A
  • H+ ions are pumped out of companion cells
  • H+ ions return to companion cell with sucrose down diffusion gradient through co-transporter protein
    sucrose diffuses into sieve tube elements through plasmodesmata
  • water potential in sieve tube decreases so water moves in by osmosis
  • hydrostatic pressure in sieve tube at source increases
  • sugary fluid moves down tube from high H pressure to low (source to sink)
  • sucrose molecules move from sieve tube into surrounding cells by facilitated diffusion or active transport
  • water moves out of sieve tube by osmosis
60
Q

what is the translocation ringing experiment?

A

ring of bark scraped away
removes phloem
bulge of sugar forms above ring as cannot be transported down stem
suggests sugar moves down stem in phloem

61
Q

what is the translocation aphids experiment?

A

aphids have specialised mouthparts called stylets which penetrate phloem tubes
aphids are anaesthetised with CO2 and stylet cut off so it remains in phloem
pure phloem sap can be collected through stylet for analysis

62
Q

what is the translocation radioactive tracers experiment (aphids)?

A

radioactive CO2 placed in bag and surrounds leaf
CO2 is incorporated into sugars and transported in the phloem
aphids feeding on sugar in phloem can be used to trace the movement of the sugar in plant from source to sink

63
Q

what is the translocation radioactive tracers experiment (autoradiography)?

A

leaf is surrounded with radioactive labelled CO2
source and sink leaves are placed firmly on photographic film in dark for 24 hours
when film is developed, presence of radioactivity shows fogging of the negatives
shows sugar transported up and down the stem

bio component 3 (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions