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Flashcards in Class 2 Deck (133):
1

water makes up most of the -- of plant cells

mass

2

water makes the bulk of the content of -- and --

vacuole and tissues

3

plant must maintain its hydration within -- or growth will cease and tissue becomes stressed, and plant may wilt or die

narrow limits

4

In lettuce, water may = --% of plant fresh mass

95

5

In wood, water may = --%

35-75

6

seed are --% water

5-15

7

because water content fluctuates diurnally, seasonally, and ontogenetically, plant growth is typically measured in -- mass

dry

8

as plants lose water, their final defense system/active response leads to the production of stress hormones

abscisic acid and solute accumulation

9

1st process that tapers off as water is lost

cell expansion

10

decrease in cell expansion is followed by a decrease in --

wall and protein synthesis

11

water is lost, stomata closes, then -- stops

photosynthesis

12

-- water potential = dehydration

negative

13

potential of pure water

-0

14

Why do plants need so much water? Water is lost as a side-effect of photosynthesis

transpirational cost

15

1 mol CO2 --> lose -- molecules of water

100

16

Opening up stomata to get CO2 for photosynthesis exposes the moist plant interior to the drying air, creating a huge driving force for water to -- out of leaf (transpiration)

evaporate

17

transpiration can cool the leaf several degrees below --

air temperature

18

Transpiration takes a huge amount of water, when transpiring under full sun, a leaf can exchange its total water content in -- minutes

20

19

a small fraction of the water taken up is used for -- and --

photosynthesis and tissue expansion

20

On a warm, dry, sunny, day a leaf will exchange up to 100 % of its water in

an hour

21

evaporation of water during transpiration -- heat energy, keeping plants under bright sunlight up to a few degrees cooler than air

dissipates

22

transpiration is a form of -- cooling because it is cost free

passive

23

animal sweating is a form of -- cooling

active

24

water is a limiting yet -- resource for growth

required

25

no water > -- closes > no photosynthesis > plant overheats

stomata

26

T/F: water is the most limiting resource for agricultural and ecosystem productivity

true

27

photosynthetic rate -- once T. optimum is reached

quickly tapers off

28

photosynthesis is -- dependent

temperature

29

respiration -- as temperature increases to increase metabolism

increases exponentially

30

net carbon =

photosynthesis - respiration

31

increasing temperatures beyond T. optimum -- proteins so respiration must increase to replace -- proteins

denatured

32

decrease in water leads to a -- in crop productivity

direct decrease

33

droughts are becoming more frequent, severe, and --

unpredictable

34

T/F: droughts are found in various types of climates and habitats

true

35

accumulation of mass by an ecosystem per area per year

productivity

36

annual precipitation is measured as -- falling per ground area

volume

37

productivity has a positive linear correlation with steady increase in annual precipitation and reaches a saturation in -- area

ever wet

38

Water has about 69 queer, --, unique properties

anomalous

39

oxygen is more -- than hydrogen so there is a partial negative charge on O and a partial positive charge on Hs

electronegative

40

due to partial charges, water is a -- molecule

polar

41

weak attraction between water molecules is due to --

hydrogen bonds

42

hydrogen bonds also form between water and other molecules with -- or -- atoms

O or N

43

hydrogen bonds in water lead to -- that continually form, break up and re-form

local, ordered clusters

44

water is a super solvent due to small size of molecules and to its -- nature

polar

45

water is especially good as a solvent for -- substances and for sugars and proteins with polar groups

ionic

46

the hydrogen bonds that form between water molecules and organic ions -- the ions, and increase their solubility

stabilize

47

because of -- water has high specific heat capacity and high latent heat of vaporization

hydrogen bonding

48

specific heat is the energy required to -- the temperature

raise

49

latent heat of vaporization is the energy require to -- from liquid to gas phase

move molecules

50

most of the energy of specific heat and latent heat of vap is required to -- hydrogen bonds

break

51

because of hydrogen bonds, water molecules are strongly attached to each other

cohesion

52

-- minimizes surface area

air-water interface

53

expanding the surface requires --

breaking hydrogen bonds

54

energy required to increase the surface area

surface tension

55

surface tension influences the shape of the air-water interface, and creates a net force at the interface if it is --

curved

56

surface tension will dissolve bubbles, because the interface exerts an --

internal pressure (2T/r)
T = surface tension of liquid
r = radius of bubble

57

air in a bubble resists shrinkage, but as the air dissolves into water, the bubble -- due to surface tension

collapses

58

water is also attracted to solid phase, especially with charged groups (e.g. cell wall, glass surface)

adhesion

59

cohesion, adhesion, and surface tension result in --

capillarity

60

surface tension, normal to the surface, is not related to -- of a fluid

viscosity

61

surface tension causes bubbles to be -- and causes air bubbles to dissolve

round

62

T/F: a sealed syringe can be used to create positive and negative presses in fluids such as water

true

63

water is driven to climb walls of a container by --

adhesion

64

high surface tension leads to -- of air-water interface

minimizing

65

-- pulls the rest of the water upward

cohesion

66

water will rise until the force is balanced by the -- of the water column

weight

67

water rises higher in -- tubes

smaller

68

in cell walls, capillaries have a tiny radius (about 100 nm) so pull water in very -- and cell wall surfaces remain wet throughout the plant

strongly

69

capillarity may contribute to water movement from soil to leaves in -- but not in tall trees

seedlings

70

-- gives water a high tensile strength

cohesion

71

the pull a continuous column of water can withstand before breaking, allowing water to be pulled like a rope

tensile strength

72

pull = -- = tension

negative pressure

73

pressure =

force per area

74

SI units of pressure

Pascals (Pa)

75

1 Pascal = 1 --

Nm^(-2)

76

0.1013 MPa Pa = 1.013 x 10^(5) kPa = 1 atmosphere = 1.013 bar = -- mm HG

760

77

1 atmosphere = -- pounds per square inch

14.7

78

pressure units used by physiologists

MPa

79

a car tire is typically inflated to about

0.2 MPa (2 bars)

80

water pressure in home plumbing

0.2-0.3 MPa (above atmospheric pressure)

81

hydraulic head for 10 m of water

0.1 MPa

82

negative pressure can develop in water; if there are no air bubbles, water can develop tensions to below --

-30 MPa

83

if air bubble contaminates the water, the bubble will expand under tension, breaking the water column

cavitation

84

tensions are very important as -- pulls water from roots to the leaves

transpiration

85

water transpiration through xylem can rise by capillary rise up about -- m

0.6

86

T/F: you can pull on air

false

87

if there's air bubble in a syringe, it will -- under tension

expand

88

if you remove all air out of water you can pull water up --

kilometers

89

remove all air molecules from water

degassing

90

used by mechanics

pounds per square inch

91

labs usually use

mm Hg

92

physiology labs

bar

93

physiology publishing

MPa

94

sucking as hard as you can, how much negative pressure can you pull?

- 0.1 MPa

95

we can theoretically pull a --

vacuum

96

leave of a plant can pull --

-0.2 MPa

97

water transport: any -- requires a driving force and a transport

flow

98

diffusion is only relevant for very -- distances

short

99

driving force in diffusion

concentration gradient (delta c / delta x)

100

transport coefficient in diffusion

diffusion coefficient (D)

101

Fick's law, flow =

-D (delta c / delta x)

102

Fick's law can be explained due simply to random --

thermal agitation

103

D is a property of the -- and the medium

diffusing substance

104

Because concentration gradient drops off rapidly with distance, diffusion is rapid over -- distances

short

105

diffusion is -- over long distances

slow

106

time to diffuse a distance L is equal to

(L^2)/D

107

a glucose molecule will take -- seconds to diffuse across a 50 um cell

2.5

108

a glucose molecule will take -- to diffuse across 1 m

32 years

109

diffusion is important for transpiration from leaves to air, movement of -- within cells, movement of signal molecules across plasmodesmata

solutes

110

driving force in bulk flow

pressure gradient (delta water potential / delta x)

111

transport coefficient in bulk flow

hydraulic conductance (K,h)

112

Darcy's Law, flow =

K,h (delta water potential / delta x)

113

for tubes like xylem conduits, Poiseuille's Law defines K,h as

[(pi)r^4]/8n

114

bulk flow -- with the width of the tube

dramatically increases

115

bulk flow is important for movement of -- in xylem and phloem, through roots, stems and leaves

sap

116

bulk flow is also important for the movement of water in the soil and through plant --

cell walls

117

driving force in osmosis

water potential gradient (delta water potential)

118

transport coefficient in osmosis

membrane conductivity (L,p)

119

osmosis equation, flow =

L,p (delta water potential)

120

cell membranes are --

selectively permeable

121

water crosses membranes by -- through lipid bilayer and through aquaporins

diffusion

122

driving force for movement of water (water potential gradient) is osmosis which is determined by both -- and -- gradient

concentration and pressure

123

water potential concept water flows from

water flows from high to low water potential

124

more solutes -- the solute potential and thus -- the overall water potential

lower

125

solute potential is either -- or negative

0

126

pressure potential can be -- in xylem, or turgor pressure in cells (pressure of water in vacuole and cytoplasm against the plant cell water)

fluid pressure

127

in open water, pressure potential is

0

128

in living cells, pressure potential is either 0 or

positive

129

in xylem, pressure potential is usually

negative

130

causes water to move downward

gravity potential

131

T/F: gravity potential is negligible at the scale of the cell

true

132

gravity potential is either 0 or --

negative

133

at -- water potential of cell and surroundings are the same there is no net water movement

equilibrium