Class 2 Flashcards
1
Q
water makes up most of the – of plant cells
A
mass
2
Q
water makes the bulk of the content of – and –
A
vacuole and tissues
3
Q
plant must maintain its hydration within – or growth will cease and tissue becomes stressed, and plant may wilt or die
A
narrow limits
4
Q
In lettuce, water may = –% of plant fresh mass
A
95
5
Q
In wood, water may = –%
A
35-75
6
Q
seed are –% water
A
5-15
7
Q
because water content fluctuates diurnally, seasonally, and ontogenetically, plant growth is typically measured in – mass
A
dry
8
Q
as plants lose water, their final defense system/active response leads to the production of stress hormones
A
abscisic acid and solute accumulation
9
Q
1st process that tapers off as water is lost
A
cell expansion
10
Q
decrease in cell expansion is followed by a decrease in –
A
wall and protein synthesis
11
Q
water is lost, stomata closes, then – stops
A
photosynthesis
12
Q
– water potential = dehydration
A
negative
13
Q
potential of pure water
A
-0
14
Q
Why do plants need so much water? Water is lost as a side-effect of photosynthesis
A
transpirational cost
15
Q
1 mol CO2 –> lose – molecules of water
A
100
16
Q
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)
A
evaporate
17
Q
transpiration can cool the leaf several degrees below –
A
air temperature
18
Q
Transpiration takes a huge amount of water, when transpiring under full sun, a leaf can exchange its total water content in – minutes
A
20
19
Q
a small fraction of the water taken up is used for – and –
A
photosynthesis and tissue expansion
20
Q
On a warm, dry, sunny, day a leaf will exchange up to 100 % of its water in
A
an hour
21
Q
evaporation of water during transpiration – heat energy, keeping plants under bright sunlight up to a few degrees cooler than air
A
dissipates
22
Q
transpiration is a form of – cooling because it is cost free
A
passive
23
Q
animal sweating is a form of – cooling
A
active
24
Q
water is a limiting yet – resource for growth
A
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
