Class 2 Flashcards
water makes up most of the – of plant cells
mass
water makes the bulk of the content of – and –
vacuole and tissues
plant must maintain its hydration within – or growth will cease and tissue becomes stressed, and plant may wilt or die
narrow limits
In lettuce, water may = –% of plant fresh mass
95
In wood, water may = –%
35-75
seed are –% water
5-15
because water content fluctuates diurnally, seasonally, and ontogenetically, plant growth is typically measured in – mass
dry
as plants lose water, their final defense system/active response leads to the production of stress hormones
abscisic acid and solute accumulation
1st process that tapers off as water is lost
cell expansion
decrease in cell expansion is followed by a decrease in –
wall and protein synthesis
water is lost, stomata closes, then – stops
photosynthesis
– water potential = dehydration
negative
potential of pure water
-0
Why do plants need so much water? Water is lost as a side-effect of photosynthesis
transpirational cost
1 mol CO2 –> lose – molecules of water
100
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
transpiration can cool the leaf several degrees below –
air temperature
Transpiration takes a huge amount of water, when transpiring under full sun, a leaf can exchange its total water content in – minutes
20
a small fraction of the water taken up is used for – and –
photosynthesis and tissue expansion
On a warm, dry, sunny, day a leaf will exchange up to 100 % of its water in
an hour
evaporation of water during transpiration – heat energy, keeping plants under bright sunlight up to a few degrees cooler than air
dissipates
transpiration is a form of – cooling because it is cost free
passive
animal sweating is a form of – cooling
active
water is a limiting yet – resource for growth
required
no water > – closes > no photosynthesis > plant overheats
stomata
T/F: water is the most limiting resource for agricultural and ecosystem productivity
true
photosynthetic rate – once T. optimum is reached
quickly tapers off
photosynthesis is – dependent
temperature
respiration – as temperature increases to increase metabolism
increases exponentially
net carbon =
photosynthesis - respiration
increasing temperatures beyond T. optimum – proteins so respiration must increase to replace – proteins
denatured
decrease in water leads to a – in crop productivity
direct decrease
droughts are becoming more frequent, severe, and –
unpredictable
T/F: droughts are found in various types of climates and habitats
true
accumulation of mass by an ecosystem per area per year
productivity
annual precipitation is measured as – falling per ground area
volume
productivity has a positive linear correlation with steady increase in annual precipitation and reaches a saturation in – area
ever wet
Water has about 69 queer, –, unique properties
anomalous
oxygen is more – than hydrogen so there is a partial negative charge on O and a partial positive charge on Hs
electronegative
due to partial charges, water is a – molecule
polar
weak attraction between water molecules is due to –
hydrogen bonds
hydrogen bonds also form between water and other molecules with – or – atoms
O or N
hydrogen bonds in water lead to – that continually form, break up and re-form
local, ordered clusters
water is a super solvent due to small size of molecules and to its – nature
polar
water is especially good as a solvent for – substances and for sugars and proteins with polar groups
ionic
the hydrogen bonds that form between water molecules and organic ions – the ions, and increase their solubility
stabilize
because of – water has high specific heat capacity and high latent heat of vaporization
hydrogen bonding
specific heat is the energy required to – the temperature
raise
latent heat of vaporization is the energy require to – from liquid to gas phase
move molecules
most of the energy of specific heat and latent heat of vap is required to – hydrogen bonds
break
because of hydrogen bonds, water molecules are strongly attached to each other
cohesion
– minimizes surface area
air-water interface
expanding the surface requires –
breaking hydrogen bonds
energy required to increase the surface area
surface tension
surface tension influences the shape of the air-water interface, and creates a net force at the interface if it is –
curved
surface tension will dissolve bubbles, because the interface exerts an –
internal pressure (2T/r) T = surface tension of liquid r = radius of bubble
air in a bubble resists shrinkage, but as the air dissolves into water, the bubble – due to surface tension
collapses
water is also attracted to solid phase, especially with charged groups (e.g. cell wall, glass surface)
adhesion
cohesion, adhesion, and surface tension result in –
capillarity
surface tension, normal to the surface, is not related to – of a fluid
viscosity
surface tension causes bubbles to be – and causes air bubbles to dissolve
round
T/F: a sealed syringe can be used to create positive and negative presses in fluids such as water
true
water is driven to climb walls of a container by –
adhesion
high surface tension leads to – of air-water interface
minimizing
– pulls the rest of the water upward
cohesion
water will rise until the force is balanced by the – of the water column
weight
water rises higher in – tubes
smaller
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
capillarity may contribute to water movement from soil to leaves in – but not in tall trees
seedlings
– gives water a high tensile strength
cohesion
the pull a continuous column of water can withstand before breaking, allowing water to be pulled like a rope
tensile strength
pull = – = tension
negative pressure
pressure =
force per area
SI units of pressure
Pascals (Pa)
1 Pascal = 1 –
Nm^(-2)
0.1013 MPa Pa = 1.013 x 10^(5) kPa = 1 atmosphere = 1.013 bar = – mm HG
760
1 atmosphere = – pounds per square inch
14.7
pressure units used by physiologists
MPa
a car tire is typically inflated to about
0.2 MPa (2 bars)
water pressure in home plumbing
0.2-0.3 MPa (above atmospheric pressure)
hydraulic head for 10 m of water
0.1 MPa
negative pressure can develop in water; if there are no air bubbles, water can develop tensions to below –
-30 MPa
if air bubble contaminates the water, the bubble will expand under tension, breaking the water column
cavitation
tensions are very important as – pulls water from roots to the leaves
transpiration
water transpiration through xylem can rise by capillary rise up about – m
0.6
T/F: you can pull on air
false
if there’s air bubble in a syringe, it will – under tension
expand
if you remove all air out of water you can pull water up –
kilometers
remove all air molecules from water
degassing
used by mechanics
pounds per square inch
labs usually use
mm Hg
physiology labs
bar
physiology publishing
MPa
sucking as hard as you can, how much negative pressure can you pull?
- 0.1 MPa
we can theoretically pull a –
vacuum
leave of a plant can pull –
-0.2 MPa
water transport: any – requires a driving force and a transport
flow
diffusion is only relevant for very – distances
short
driving force in diffusion
concentration gradient (delta c / delta x)
transport coefficient in diffusion
diffusion coefficient (D)
Fick’s law, flow =
-D (delta c / delta x)
Fick’s law can be explained due simply to random –
thermal agitation
D is a property of the – and the medium
diffusing substance
Because concentration gradient drops off rapidly with distance, diffusion is rapid over – distances
short
diffusion is – over long distances
slow
time to diffuse a distance L is equal to
(L^2)/D
a glucose molecule will take – seconds to diffuse across a 50 um cell
2.5
a glucose molecule will take – to diffuse across 1 m
32 years
diffusion is important for transpiration from leaves to air, movement of – within cells, movement of signal molecules across plasmodesmata
solutes
driving force in bulk flow
pressure gradient (delta water potential / delta x)
transport coefficient in bulk flow
hydraulic conductance (K,h)
Darcy’s Law, flow =
K,h (delta water potential / delta x)
for tubes like xylem conduits, Poiseuille’s Law defines K,h as
[(pi)r^4]/8n
bulk flow – with the width of the tube
dramatically increases
bulk flow is important for movement of – in xylem and phloem, through roots, stems and leaves
sap
bulk flow is also important for the movement of water in the soil and through plant –
cell walls
driving force in osmosis
water potential gradient (delta water potential)
transport coefficient in osmosis
membrane conductivity (L,p)
osmosis equation, flow =
L,p (delta water potential)
cell membranes are –
selectively permeable
water crosses membranes by – through lipid bilayer and through aquaporins
diffusion
driving force for movement of water (water potential gradient) is osmosis which is determined by both – and – gradient
concentration and pressure
water potential concept water flows from
water flows from high to low water potential
more solutes – the solute potential and thus – the overall water potential
lower
solute potential is either – or negative
0
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
in open water, pressure potential is
0
in living cells, pressure potential is either 0 or
positive
in xylem, pressure potential is usually
negative
causes water to move downward
gravity potential
T/F: gravity potential is negligible at the scale of the cell
true
gravity potential is either 0 or –
negative
at – water potential of cell and surroundings are the same there is no net water movement
equilibrium
