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EEB 162 > Class 3 > Flashcards

Class 3 Flashcards

1
Q

simplest index of water status

A

relative water content

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2
Q

relative water content = – / (saturated mass - dry mass) x 100%

A

fresh mass - dry mass

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3
Q

one weakness of RWC is that it is not very – for measuring drought responses

A

sensitive

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4
Q

leaves can show strong responses to – change in RWC

A

less than 2 percent

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5
Q

one weakness of RWC is that it tells us nothing about the – for water movement

A

forces

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6
Q

– is another index of water status, that is correlated with RWC but lacks RWC’s weaknesses

A

water potential

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7
Q

an overall, average water potential of the whole leaf, as the collection of all the leaf cells

A

leaf water potential

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8
Q

leaf water potential can be measured with the –

A

pressure bomb

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9
Q

for leaves of well watered plants, leaf water potential ranges from –

A

-0.2 MPa to -2 MPa

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10
Q

plants of arid climates of saline environments can function at much lower leaf water potential down to below – due to accumulating solutes in the cells, producing a very negative solute potential

A

-5 MPa

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11
Q

plant growth requires that cells have – turgor pressure

A

positive (pressure potential > 0)

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12
Q

as cells lose water, pressure potential – quickly until turgor is lost (solute potential declines linearly)

A

drops

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13
Q

T/F: as water potential declines further, different functions cease, and eventually plants die

A

true

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14
Q

at zero turgor, unlignified tissues collapse and plants –

A

wilt

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15
Q

plot of leaf water potential versus RWC

(or sometimes - 1/leaf water potential vs RWC, or vs 100%-RWC), and sometimes includes plots of leaf osmotic (solute) potential and pressure potential versus RWC

A

pressure-volume curve

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16
Q

plotting the PV curve allows extraction of 4 main parameters: the –, determined from the intercept of the solute potential versus RWC

A

osmotic potential at full turgor

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17
Q

osmotic potential at full turgor is an index of the – of cell sap in hydrated tissue

A

saltiness

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18
Q

plotting the PV curve allows extraction of 4 main parameters: – which is the leaf water potential corresponding to the point at which the pressure potential = 0 or when the leaf water potential = solute potential

A

osmotic potential at turgor loss point

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19
Q

osmotic potential at turgor loss point is also known as – or simply turgor loss point

A

water potential at turgor loss point

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20
Q

because stomata close and cells may lose function at turgor loss, osmotic potential at turgor loss point is a – of cell, leaf and plant drought tolerance

A

predictor

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21
Q

plotting the PV curve allows extraction of 4 main parameters: – determined as the slope of pressure potential versus RWC

A

modulus of elasticity

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22
Q

modulus of elasticity is an index of the – of cell walls

A

rigidity

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23
Q

some drought tolerant plants have – elastic modulus values, but not always

A

high

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24
Q

plotting the PV curve allows extraction of 4 main parameters: – is the x-intercept of the -1/leaf water potential versus RWC curve

A

apoplastic function

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25
Q

apoplastic function represents the – in the apoplast in a hydrated leaf

A

% of water stored

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26
Q

of all the PV curve’s parameters, – is the strongest predictor of drought tolerance

A

osmotic potential at turgor loss point (water potential at turgor loss point, turgor loss point)

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27
Q

– of cell sap is a strong predictor of drought tolerance across plant species

A

saltiness

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28
Q

water diffuses from the leaf due to a – between leaf and air

A

water vapor concentration gradient (vapor pressure deficit)

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29
Q

the diffusion of water from the cell walls inside the leaf causes stretching of – which generates a tension, pulling water from the xylem

A

air-water interfaces

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30
Q

the resulting tension, from the stretching of air-water interfaces, in the xylem pulls water by – from the roots

A

bulk flow

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31
Q

water moves through soil by – driven by pressure gradients, and dependent on soil hydraulic conductivity

A

bulk flow

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32
Q

soil hydraulic conductivity depends on – and structure and how wet the soil is

A

soil type

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33
Q

clay = – particles

A

small

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34
Q

sand = – particles

A

large

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35
Q

water moves through channels between particles or as – adhering to particles

A

film

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36
Q

soil saturated with water, with excess water drained away

A

field capacity

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37
Q

field capacity occurs when water stops dripping and water potential = –

A

0

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38
Q

soil solute potential is usually close to – unless soil is very salty

A

0

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39
Q

for wet soils, pressure potential is close to –

A

0

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40
Q

as soil dries, air-water interfaces becomes stretched between soil particles generating a negative pressure because of – so pressure potential becomes negative

A

surface tension

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41
Q

in drier soils, as the films around particles become thinner, smaller radii of curvature are generated = – of the interface = stronger tension

A

greater distortion

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42
Q

when soils are – soil water potential = pressure potential = -2MPa or lower

A

dry

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43
Q

as soil dries, soil hydraulic conductivity – as channels in the soil empty of water

A

declines

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44
Q

water is more difficult to remove from drier soil both because the soil water potential is lower and because the – is lower

A

soil hydraulic conductivity

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45
Q

water moves into the root principally through –

A

root hairs

46
Q

root hairs constitute – of root surface area and principally near the root apex

A

> 60%

47
Q

roots need in contact with – to absorb water and nutrients

A

soil

48
Q

disturbance of root’s contact with soil (new root hairs needed)

A

transplant shock

49
Q

T/F: roots also need contact with air

A

true

50
Q

during flooding, airspaces are filled with water –> roots can’t respire and lose function –> plants –

A

wilt

51
Q

water moves in the root via the apoplast, transmembrane and symplast pathways until reaching the –

A

endodermis

52
Q

at the endodermis, the – has suberized radial cell walls, and the apoplastic path is blocked; water enters the symplast

A

Casparian strip

53
Q

after entering the symplast, the water moves to the –

A

xylem

54
Q

water enters cells mainly through protein channels called –

A

aquaporins

55
Q

aquaporins can be open or – in response to environmental factors

A

gated

56
Q

water pulled through xylem conduits: tracheids and vessels

A

tension-driven flow

57
Q

– are universal in vascular plants but vessels are found only in angiosperms, a gymnosperm called Gnetum and some ferns

A

tracheids

58
Q

xylem conduits are –, hollowed out cells (tubes with lignified cell walls)

A

dead

59
Q

xylem conduits make up a series connected by –

A

pits

60
Q

pits may be simple or in conifers, with a –

A

margo/torus

61
Q

xylem tubes allow a high –

A

hydraulic conductance

62
Q

because xylem acts as a tube system, flow are – times faster than if water had to move cell-to-cell to the top of tall tress

A

10 billion

63
Q

hydraulic conductance is related to the – power of the radii of the conduit so vessels are MUCH more conductive than tracheids and allow much more rapid flows of water to the leaf

A

4th

64
Q

water drawn up to the top of trees by tensions in the xylem

A

cohesion-tension theory

65
Q

challenge to the plant: cavitation by –

A

air-seeding

66
Q

air is drawn into xylem conduits through – from surrounding airspaces

A

pits

67
Q

Or during –, air may come out of solution

A

cooling/freezing

68
Q

when air bubbles enter the xylem, they – in the water under tension, and fill the xylem conduit, rendering it useless

A

expand

69
Q

when air bubbles enter the xylem, they expand in the water under tension, and fill the xylem conduit –> xylem conduit must be – or it loses function forever

A

refilled

70
Q

T/F: water can move in conduits around the air-filled conduit

A

true

71
Q

one way refilling takes place is by – the stomata

A

closing

72
Q

one way refilling takes place is by –

A

root pressure

73
Q

root pressure is found in some, but not all plants, sometimes only –

A

seasonally

74
Q

roots transport solutes into the xylem, which draws in water, which – the pressure in the xylem

A

increases

75
Q

the pressurized water in the xylem dissolves air bubbles, and when air is moist, and transpiration is low, water may eventually – from hydathodes in the leaves

A

guttate

76
Q

the tension in the xylem is produced by the – of water from cells and surface tension

A

evaporation

77
Q

the – the radii of curvature the greater the deformation of the interface and the stronger the tension

A

smaller

78
Q

water from the cell walls evaporates into – and diffuses through the leaf and out of stomata

A

airspaces

79
Q

only – of water evaporates through the cuticle

A

less than 5 percent

80
Q

leaf is full of airspace (up to 50% of leaf volume) to allow rapid diffusion of – into the leaf and also allows rapid diffusion of water out of the leaf

A

CO2

81
Q

the average water molecule evaporated in the leaf travels – outside, which would take 0.04 s by diffusion calculation

A

1mm

82
Q

the concentration gradient driving the diffusion of vapor out of the leaf is –

A

strong

83
Q

leaves have large internal wet – (up to 50 x external leaf area) so air inside the leaf is considered to be close to saturation (close to 100% relative humidity)

A

mesophyll surface

84
Q

saturation water concentration increases exponentially with –

A

temperature

85
Q

higher temperature – leaf-to-air concentration gradient

A

higher

86
Q

T/F: moist air is ‘dry’ enough to drive strong transpiration

A

true

87
Q

at 20 degrees Celsius, air at RH = 95% is the equivalent of – MPa

A

-7

88
Q

when air is at RH = 50%, the driving force is equivalent of – MPa

A

-94

89
Q

transpiration occurs through the –

A

stomata

90
Q

transpiration: the diffusion through pores depends on the concentration gradient (VPD), on the diffusion coefficient (D), and the –

A

diffusional resistance

91
Q

diffusional resistance = – + boundary layer resistance

A

stomatal resistance

92
Q

stomatal resistance depends on the total area of –

A

stomatal pore

93
Q

stomatal resistance – as stomata close

A

increases

94
Q

boundary layer resistance depends on leaf size and –

A

windspeed

95
Q

a smaller leaf and higher windspeed lead to a thinner boundary layer with – resistance

A

lower

96
Q

leaf shape and – can also influence boundary layer resistance

A

hairiness

97
Q

at high windspeed, the boundary later is very thin and – becomes the major influence on diffusional resistance and on transpiration

A

stomatal resistance

98
Q

at low windspeed, the – is the major influenceon diffusional resistance and on transpiration

A

boundary layer resistance

99
Q

at low windspeed, transpiration is relatively – stomatal resistance, except when this becomes very high because stomata are nearly closed

A

insensitive

100
Q

T/F: stomata evolved once for all plants, in a distant ancestor

A

true

101
Q

stomata are required for control of – relative to CO2 gain

A

water loss

102
Q

plants can thus open pores to fix carbon when water is abundant, but close pores to save water from the water supply is low, or when the leaf demand for CO2 is –

A

low

103
Q

stomata are controlled via – swelling

A

guard cell

104
Q

guard cells are – shaped in grasses and kidney-shaped in non-grasses

A

dumbbell

105
Q

differential wall thickening and arrangement of – dictates which parts of the guard cells will stay fixed

A

cellulose microfibrils

106
Q

as the rest of the cell swells, pores open when guard cells are –

A

pressurized

107
Q

guard cells are pressurized by increasing – in the cell via ion uptake or creating new organic ions in the cells

A

solute potential

108
Q

increasing solute potential in the guard cells, drives water uptake from the surrounding mesophyll, and pressure potential increases and the cells –

A

swell

109
Q

guard cell turgor is sensitive to light, –, leaf water status, and CO2 concentration

A

temperature

110
Q

the guard cells are kept isolated from surrounding cells (no plasmodesmata), so their aperture is – dictated by the water status of surrounding cells

A

not directly

111
Q

overall soil-plant-atmosphere continuum: water moves through soil and xylem by – and out of leaves by diffusion

A

bulk flow

112
Q

there is a water potential – (1) across the entire plant, and (2) between any two tissues in the flow pathway, from the soil to the leaf airspaces

A

drop

EEB 162 (17 decks)

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