Plant water relations

1. 11
Principles of plant physiology Principles of plant physiology
Chapter TwoChapter Two
Plant-Water RelationsPlant-Water Relations
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Water is absolutely essential for all living Water is absolutely essential for all living
organisms.organisms.
Why is water importantWhy is water important? ?
–Living cells are composed of 70-95 % waterLiving cells are composed of 70-95 % water
–Life absolutely depends on the properties of Life absolutely depends on the properties of
water.water.
–Life probably evolved in water. Life probably evolved in water.
–water covers ¾ of the earthwater covers ¾ of the earth
–When organisms go dormant, they loose most of When organisms go dormant, they loose most of
their watertheir water
–Limiting resource for crop productivity Limiting resource for crop productivity
AgricultureAgriculture
– Water naturally exists in all three physicalWater naturally exists in all three physical
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Tom Robbins, “Tom Robbins, “Even Cowgirls Get the Blues”Even Cowgirls Get the Blues”
•Water-the ace of elementsWater-the ace of elements
–Water dives from the clouds without Water dives from the clouds without parachute, wings or parachute, wings or
safety net safety net
–Water runs over the steepest precipice Water runs over the steepest precipice and blinks not a and blinks not a
lash lash
–Water is Water is buried and rises againburied and rises again; water ; water walks on firewalks on fire and fire and fire
gets the blisters gets the blisters
–Stylishly composed in any situation - solid, gas or liquid Stylishly composed in any situation - solid, gas or liquid
–speaking in penetrating dialects understood by all things - speaking in penetrating dialects understood by all things -
animal, vegetable or mineral animal, vegetable or mineral
–water travels intrepidly through three dimensions:water travels intrepidly through three dimensions:
•sustaining, sustaining,
•destroying, and destroying, and
•creatingcreating
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1.1 Properties of water important to 1.1 Properties of water important to
plantplant
 Life is absolutely dependent on the properties of water
 Pure water: Colourless and has no smell and taste
 The hidden qualities of water make it a most interesting:
Physicochemical properties of water
I. Water is polar
Water's unique properties due to its simple composition and
structure
 hydrogen atoms are "attached" to one side of the oxygen hydrogen atoms are "attached" to one side of the oxygen
atomatom
 Positive and negative charge Positive and negative charge
 The separation between negative and positive charges The separation between negative and positive charges
creates a polar molecule creates a polar molecule
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II. Hydrogen bondsII. Hydrogen bonds
 A weak bond that forms between a hydrogen atom A weak bond that forms between a hydrogen atom
and electronegative atomand electronegative atom
 Water can bond both to itself and to other moleculesWater can bond both to itself and to other molecules
 responsible for the responsible for the thermal properties of waterthermal properties of water
A.A.Water's high specific heat capacity Water's high specific heat capacity
the amount of heat energy that must be the amount of heat energy that must be added or added or
lostlost to change the temperature of one gram of water to change the temperature of one gram of water
by 1°Cby 1°C
water can absorb a lot of heat before water water can absorb a lot of heat before water
molecules can move faster or begin to get hot molecules can move faster or begin to get hot
much more energy is needed disrupt the hydrogen much more energy is needed disrupt the hydrogen
bonds in liquid waterbonds in liquid water
•water resists rapid temperature fluctuations water resists rapid temperature fluctuations
•adding stability to earth's environments adding stability to earth's environments Beira Hailu Meressa, JUCAVM Beira Hailu Meressa, JUCAVM
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B.B. high heat of vaporizationhigh heat of vaporization
the energy needed to change the phase of a liquid to a
gas  (44 kJ/mole)
it takes a great deal of energy to break a molecule free
of its liquid partners
–water resists evaporation
–causes a cooling effect on plants
C. High latent heat of fusionC. High latent heat of fusion
takes lots of energy to convert from solid to a liquid takes lots of energy to convert from solid to a liquid
statestate
lot of energy must be released by water to freezelot of energy must be released by water to freeze
Thus water resists freezing Thus water resists freezing
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D. Capillary actionD. Capillary action
i.i. CohesionCohesion
hydrogen bonds between water molecules make hydrogen bonds between water molecules make
liquid water self-stickyliquid water self-sticky
The hydrogens of one water molecule are attracted The hydrogens of one water molecule are attracted
to the oxygen from other water moleculesto the oxygen from other water molecules
makes water bead up more on a surface makes water bead up more on a surface
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ii. Adhesionii. Adhesion
the attraction of water molecules to non-water the attraction of water molecules to non-water
hydrophilic substanceshydrophilic substances
This property of water gives it the ability to climb This property of water gives it the ability to climb
the wall of any container it is in the wall of any container it is in
The top of the water column assumes a The top of the water column assumes a uu-shape-shape
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iii. Surface tensioniii. Surface tension
Water has a very high surface tension Water has a very high surface tension
the cohesion of water molecules to each the cohesion of water molecules to each
other and to the water molecules below at the other and to the water molecules below at the
surface of a body of water surface of a body of water
It is a measure of how difficult it is to break It is a measure of how difficult it is to break
the surface of a liquid the surface of a liquid
Thus water acts as thought it has a skin Thus water acts as thought it has a skin
because of cohesion because of cohesion
Plants take advantage of capillary action to Plants take advantage of capillary action to
pull water from the root into themselves pull water from the root into themselves
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III. Universal solventIII. Universal solvent
dissolves more different kinds of dissolves more different kinds of
substances than any other solventsubstances than any other solvent
Hydrogen bonds make water an Hydrogen bonds make water an
excellent solvent excellent solvent
wherever water goes, either through the wherever water goes, either through the
ground or through plant body, it takes ground or through plant body, it takes
along valuable chemicals, minerals, and along valuable chemicals, minerals, and
nutrients. nutrients.
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Water is a versatile solvent owing to its polarityWater is a versatile solvent owing to its polarity
Ionic compounds dissolve in water. Ionic compounds dissolve in water.
•Charged regions of polar water molecules Charged regions of polar water molecules
have an electrical attraction to charged ions have an electrical attraction to charged ions
•Water surrounds individual ions, separating Water surrounds individual ions, separating
and shielding them from one another and shielding them from one another
Polar compounds in general, are water-soluble. Polar compounds in general, are water-soluble.
Charged regions of polar water molecules have an Charged regions of polar water molecules have an
affinity for opposite charged regions of other polar affinity for opposite charged regions of other polar
molecules molecules
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IV. Water is a liquid at physiological IV. Water is a liquid at physiological
temperaturetemperature
 high boiling and melting point when compared to high boiling and melting point when compared to
other similar sized moleculesother similar sized molecules
 Life exists between 0 and 100Life exists between 0 and 100
oo
C C
<0<0
oo
C too low to permit significant chemistry for C too low to permit significant chemistry for
metabolismmetabolism
> > 100 oC tends to disrupt bonds100 oC tends to disrupt bonds
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VV. Transparent to Light. Transparent to Light
Chloroplasts inside a cell are Chloroplasts inside a cell are
surrounded by watersurrounded by water
Photosynthesis if water were Photosynthesis if water were
opaque ????opaque ????
the penetration of light in water the penetration of light in water
determines the distribution of aquatic determines the distribution of aquatic
plantsplants
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VI. Chemically inertVI. Chemically inert::
water does not react unless enzymaticcally water does not react unless enzymaticcally
designed to react designed to react
VII. Affect the shape, stability and VII. Affect the shape, stability and
properties of biological molecules.properties of biological molecules.
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Role of Water in plantsRole of Water in plants
Solvent for the uptake and transport of molecules Solvent for the uptake and transport of molecules
Water is major component of cellsWater is major component of cells
Good medium for biochemical reactionsGood medium for biochemical reactions
React in many biochemical reaction React in many biochemical reaction
Provide structural support via turger pressure in leavesProvide structural support via turger pressure in leaves
The medium for the transfer of plant gamete The medium for the transfer of plant gamete
Plant movements are the result of water moving in to Plant movements are the result of water moving in to
and out of those plants and out of those plants
Temperature stabilization Temperature stabilization
Plays a role in cell elongation and growthPlays a role in cell elongation and growth Beira Hailu Meressa, JUCAVM Beira Hailu Meressa, JUCAVM
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2.22.2 Concepts of water potentialConcepts of water potential
diverse multivarious role of water in diverse multivarious role of water in
plant function plant function
Consider both Consider both
the state of water andthe state of water and
rate of movement of water in plantsrate of movement of water in plants
determined by values of water potential determined by values of water potential
or gradient in water potentialor gradient in water potential
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Defn. Defn. is the chemical potential of water in a is the chemical potential of water in a
solutionsolution compared to compared to pure waterpure water at the same at the same
temperature and pressuretemperature and pressure
a measure of the free energy of watera measure of the free energy of water
the energy available to move the energy available to move waterwater from one from one
place to another place to another
with out temperature change with out temperature change
Determines direction of water movement Determines direction of water movement
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Values of water potential:Values of water potential:
Pure water has a defined water Pure water has a defined water
potential of zero. potential of zero.
However it is possible for the water However it is possible for the water
potential to be potential to be positivepositive or or negativenegative
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Units of measurementUnits of measurement: :
measured in units of atmospheric measured in units of atmospheric
pressure:pressure:
 Pascal (MPa)Pascal (MPa)
 Pounds force/square inchPounds force/square inch
 Bars Bars
 dynes/square cmdynes/square cm
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Equation of water potentialEquation of water potential
In a simple system In a simple system
•Pressure potential (Ψp) Pressure potential (Ψp)
•Osmotic potential(Ψπ) or solute potential Osmotic potential(Ψπ) or solute potential
(Ψ(Ψss).).
Ψ = Ψp + Ψπ (Ψs)Ψ = Ψp + Ψπ (Ψs)
Complex Systems Complex Systems
Gravity potential (Ψg)Gravity potential (Ψg)
Matric potential (Ψm)Matric potential (Ψm)
Ψ = Ψπ + Ψp + Ψg + Ψm Ψ = Ψπ + Ψp + Ψg + Ψm
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A. Solute potential / osmotic potential/A. Solute potential / osmotic potential/
A measure of tendency for HA measure of tendency for H
22O to cross a O to cross a
selectively permeable membraneselectively permeable membrane
from low concentration to high from low concentration to high
concentration of soluteconcentration of solute
Pure water has a solute potential of Pure water has a solute potential of zerozero
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Addition of solute makes the value of Addition of solute makes the value of
solute potential negative solute potential negative
decreasesdecreases the free energy of water the free energy of water
Negative contribution to water potential Negative contribution to water potential

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Van’t Hoff equationVan’t Hoff equation
Shows relationship of solute concentration Shows relationship of solute concentration
(in molality) to solute potential(in molality) to solute potential
Ψπ = − miRTΨπ = − miRT
m, m, concentration of the soluteconcentration of the solute
i i , ionization constant of the solute (1 for , ionization constant of the solute (1 for
glucose, 2 for NaCl)glucose, 2 for NaCl)
RR , ideal gas constant , ideal gas constant
T T , temperature (K), temperature (K)
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For example, For example,
when a solute is dissolved in waterwhen a solute is dissolved in water
the water molecules are less likely to the water molecules are less likely to
diffuse away via osmosis than when diffuse away via osmosis than when
there is no solutethere is no solute

SSSSSS
WWWW
SSSSSS
WWWW
SSSSSS
WWWW
High free energy of water ?????
A
B
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•m
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•less free energy,
less free energy,
•less positive,
less positive,
•high solute
high solute
Water movement
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B. Pressure potential (turgor pressure) (Ψp)B. Pressure potential (turgor pressure) (Ψp)
•the hydrostatic pressure produced by a the hydrostatic pressure produced by a
solution in a space divided by a solution in a space divided by a
differentially permeable membranedifferentially permeable membrane
•due to a differential in the concentrations due to a differential in the concentrations
of solute of solute
•is increased as water enters a plant cell is increased as water enters a plant cell
•It is usually positiveIt is usually positive
•may be negative (tension) as in the xylemmay be negative (tension) as in the xylem
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•When a biological cell is in a hypotonic When a biological cell is in a hypotonic
environment (the cell interior contains a environment (the cell interior contains a
lower concentration of water)lower concentration of water)
•water flows across the cell membrane into water flows across the cell membrane into
the cellthe cell
•expand due to an increases in the total expand due to an increases in the total
amount of water inside the cell amount of water inside the cell
•exerts a pressure on the cell wall exerts a pressure on the cell wall
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Hypotonic
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C. Matric potential C. Matric potential (Ψm)(Ψm)
•due to the force of attraction of water for due to the force of attraction of water for
colloidal, charged surfaces colloidal, charged surfaces
•It is negative because it reduces the ability of It is negative because it reduces the ability of
water to move water to move
•In large volumes of water it is very small and In large volumes of water it is very small and
usually ignored usually ignored
•Water adheres electrostatically to solid Water adheres electrostatically to solid
hydrophilic surface hydrophilic surface
•Capillary rise is associated with matrix potential. Capillary rise is associated with matrix potential.
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D.D. Gravitational potential (ΨgΨg)
•The potential energy associated with moving The potential energy associated with moving
water to heightwater to height
•when referring to the top of tall treeswhen referring to the top of tall trees
ΨgΨg= = ρgh ρgh
= 1000kg/M= 1000kg/M
33
*9.8 m/S *9.8 m/S
22
*h(m) *h(m)
= 0.01Mpa/m= 0.01Mpa/m
water in leaves at the top of a 100m tall tree water in leaves at the top of a 100m tall tree
suck water. suck water.
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Basic principles of water potentialBasic principles of water potential
•Water potential of pure water is zero, Water potential of pure water is zero,
open to the atmosphereopen to the atmosphere
•Water potential in intact plant tissue is Water potential in intact plant tissue is
usually negative because of the large usually negative because of the large
quantities of dissolved solutes in cellsquantities of dissolved solutes in cells
•The addition of solute decreases water The addition of solute decreases water
potentialpotential
•The addition of pressure increases water The addition of pressure increases water
potentialpotential
•Pure water, under external pressure is Pure water, under external pressure is
positivepositive
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•Plant cells will gain or lose water to Plant cells will gain or lose water to
intercellular fluids depending upon their intercellular fluids depending upon their
water potentialwater potential
–A flaccid cell placed in a hyperosmotic A flaccid cell placed in a hyperosmotic
solution (low Ψw)solution (low Ψw)
–lose water by osmosis lose water by osmosis
–the cell will plasmolyze the cell will plasmolyze
–protoplast moves away from cell wallprotoplast moves away from cell wall
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•Gives a measure of water statusGives a measure of water status
–Leaves of well-watered plants have water Leaves of well-watered plants have water
potential ranging from -0.2 and -0.6Mpapotential ranging from -0.2 and -0.6Mpa
–Leaves of plants in arid climates poses Leaves of plants in arid climates poses
water potential between -2 and -5water potential between -2 and -5
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Effect on physiological changesEffect on physiological changes
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2.3 Water movement in cells and tissues2.3 Water movement in cells and tissues
Mechanisms of movementMechanisms of movement
1.1.Bulk (or Mass) FlowBulk (or Mass) Flow
•mass movement of molecules in response mass movement of molecules in response
to a to a pressure gradientpressure gradient
•The molecules move from high to low The molecules move from high to low
pressure pressure
•functions in long-distance transport functions in long-distance transport
•is usually along the vertical axis of the is usually along the vertical axis of the
plantplant
–Vascular tissues Vascular tissues
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2. Diffusion2. Diffusion
•the net random movement of individual the net random movement of individual
molecules driven by random thermal motionmolecules driven by random thermal motion
•is rapid over short distancesis rapid over short distances
a region of high a region of high
concentrationconcentration//
high chemical high chemical
potentialpotential
area of high free energy
low free energy
region of low region of low
concentrationconcentration//
low chemical low chemical
potentialpotential
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•Molecules move until they reach dynamic equilibrium
•At equilibrium the net movement stops
•the molecules continue to move randomly
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Factors influencing the rate of diffusionFactors influencing the rate of diffusion
i. Concentration Gradient i. Concentration Gradient
•Solutes move from an area of high Solutes move from an area of high
concentration to one of lower concentration to one of lower
concentrationconcentration
•Fick’s Law : relates the rate of diffusion to Fick’s Law : relates the rate of diffusion to
the concentration gradient (C1–C2) and the concentration gradient (C1–C2) and
resistance (r)resistance (r)
Js = (C1-C2)/r Js= flux densityJs = (C1-C2)/r Js= flux density
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•The rate of diffusion is directly proportional The rate of diffusion is directly proportional
to the concentration gradientto the concentration gradient
• The greater the difference in concentration The greater the difference in concentration
between two areas, the greater the rate of between two areas, the greater the rate of
diffusiondiffusion
•if the gradient is zero, there will be no net if the gradient is zero, there will be no net
diffusiondiffusion
•The greater the resistance to diffusion, the lower The greater the resistance to diffusion, the lower
the rate of diffusionthe rate of diffusion
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ii. Molecular Speedii. Molecular Speed
•atoms and molecules are always in motion at atoms and molecules are always in motion at
temperatures above absolute zero temperatures above absolute zero
•Molecular speed is directly proportional to Molecular speed is directly proportional to
temperature temperature
•At room temperature, the average velocity of a At room temperature, the average velocity of a
molecule is =2 km/sec molecule is =2 km/sec
•indirectly related to molecular weight indirectly related to molecular weight
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iii. Temperature iii. Temperature
•increases the rate of molecular increases the rate of molecular
movement movement
•therefore, increases the rate of diffusiontherefore, increases the rate of diffusion
iv. Pressureiv. Pressure
increases speed of moleculesincreases speed of molecules
increase the rate of diffusionincrease the rate of diffusion
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V. Solute effect on the chemical potential of V. Solute effect on the chemical potential of
the solventthe solvent
•Solute particles decrease the free energy Solute particles decrease the free energy
of a solvent of a solvent
•factor is the number of particles factor is the number of particles
•Mole fraction of solventMole fraction of solvent = Number of solvent = Number of solvent
molecules/total number of solvent molecules + solute molecules/total number of solvent molecules + solute
molecules molecules
Water moves from an area of higher mole Water moves from an area of higher mole
fractionfraction
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3.Osmosis3.Osmosis
•This is a specialized case of diffusion This is a specialized case of diffusion
•the diffusion of a solvent across a biological the diffusion of a solvent across a biological
selectively permeable membraneselectively permeable membrane
• Movement is driven by the sum of a Movement is driven by the sum of a
concentration gradient and pressure gradientconcentration gradient and pressure gradient
•Osmosis to occur :Osmosis to occur :
–two solutions of the same solventtwo solutions of the same solvent
–separated with selectively permeable membrane separated with selectively permeable membrane
–pressure and concentration gradientpressure and concentration gradient
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4. Dialysis:4. Dialysis:
•This is another specialized case This is another specialized case
of diffusion of diffusion
•it is the diffusion of solute across it is the diffusion of solute across
a semi-permeable membrane. a semi-permeable membrane.
High
salt
Low salt buffer
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Transport of water in Transport of water in
PlantsPlants
Levels of transport in plants:Levels of transport in plants:
Movement of water and solutes into and out Movement of water and solutes into and out
of individual cells of individual cells
Localized transport of material from cell to Localized transport of material from cell to
cell at the level of tissues and organs cell at the level of tissues and organs
Long-distance transport of sap throughout Long-distance transport of sap throughout
the vascular tissues at the whole-plant the vascular tissues at the whole-plant
level level
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Water diffuse from the Water diffuse from the soilsoil to the to the plant plant
rootroot and then to the and then to the airair : :
Water potential gradient is established Water potential gradient is established
between the root cell sap and the soil solutionbetween the root cell sap and the soil solution
Water potential may be established by:Water potential may be established by:
•Increasing the concentration of solutesIncreasing the concentration of solutes..
– Water potential of soil solution is Water potential of soil solution is
highest than airhighest than air
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•Physical state of water Physical state of water
–highest whenhighest when water is a liquid and water is a liquid and
–lowest when water is a gas in airlowest when water is a gas in air. .
intimate contact between root hair intimate contact between root hair
and soil particlesand soil particles
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Water Transport in the RootWater Transport in the Root
Water is taken in to the root hairWater is taken in to the root hair
move into and within the plant move into and within the plant
root in a variety of routs root in a variety of routs
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A.A.Apoplastic path wayApoplastic path way
movement of water through intercellular movement of water through intercellular
spaces and cell wall spaces and cell wall
continuum formed between the continuous continuum formed between the continuous
matrix of cell wallsmatrix of cell walls
Water and solute move without entering a Water and solute move without entering a
cellcell
involves the non-living vascular tissue involves the non-living vascular tissue
due to capillary action due to capillary action
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blocked by the casparian strip at blocked by the casparian strip at
endodermis endodermis
Impermeable band of suberin Impermeable band of suberin
inside walls of endodermal cells inside walls of endodermal cells
regulates the quantity and type of regulates the quantity and type of
minerals and ions reach the xylem minerals and ions reach the xylem
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B. Syplastic path wayB. Syplastic path way
the continuum of cytoplasm within a the continuum of cytoplasm within a
plant tissueplant tissue
formed by the plasmodesmata formed by the plasmodesmata
which pass through pores in the cell which pass through pores in the cell
walls. walls.
responsible in order water and responsible in order water and
minerals to reach the xylem. minerals to reach the xylem.
This path way involves the living This path way involves the living
part of the cellpart of the cell
water moves by osmosiswater moves by osmosis
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C. Transmembrane path wayC. Transmembrane path way
•Water sequentially moves from one cell Water sequentially moves from one cell
to the next cell to the next cell
•by repeatedly crossing plasma by repeatedly crossing plasma
membranes and cell walls.membranes and cell walls.
•NB. Water and solute molecules can NB. Water and solute molecules can
move move
–by any one of these routes orby any one of these routes or
–a combination through switching from one to a combination through switching from one to
anotheranother..
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Apoplast
Symplast
TransmembraneBeira Hailu Meressa, JUCAVM Beira Hailu Meressa, JUCAVM
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The xylem pathwayThe xylem pathway
1. Root Pressure1. Root Pressure
•This a push forceThis a push force
•Generated as solute accumulates in the xylemGenerated as solute accumulates in the xylem
Due to the root's active absorption of dissolved Due to the root's active absorption of dissolved
nutrients nutrients
the water in the soil tends to be lower in the water in the soil tends to be lower in
solutes than the water inside the root's cells solutes than the water inside the root's cells
solute potential gradient developssolute potential gradient develops
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water flows into the roots through osmosis and water flows into the roots through osmosis and
osmotic pressureosmotic pressure increases increases
called root pressure called root pressure
a mechanism used by vascular plants to transport a mechanism used by vascular plants to transport
water through the xylem to the plant's higher water through the xylem to the plant's higher
reachesreaches
only provide modest push water up the stemonly provide modest push water up the stem
is not enough to account for the movement of is not enough to account for the movement of
water to leaves at the top of treeswater to leaves at the top of trees
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(A)
(B)
Mineral
ions
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2. TACT Mechanism2. TACT Mechanism
The transpirational pull on the xylem sap The transpirational pull on the xylem sap
is transmitted to the soil solutionis transmitted to the soil solution
Four forces combine to transport water Four forces combine to transport water
solutions from the roots through the xylem solutions from the roots through the xylem
elements, and into the leaveselements, and into the leaves
These TACT forces are: These TACT forces are:
•Transpiration Transpiration
•Adhesion Adhesion
•Cohesion Cohesion
•Tension Tension
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i. Transpirationi. Transpiration
involves the pulling of water up involves the pulling of water up
through the xylem of a plant through the xylem of a plant
Utilize the energy of evaporation and Utilize the energy of evaporation and
the tensile strength of water. the tensile strength of water.
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ii. Adhesionii. Adhesion
 is the attractive force between water is the attractive force between water
molecules and other substances.molecules and other substances.
both water and cellulose are polar both water and cellulose are polar
moleculesmolecules
there is a strong attraction for water to the there is a strong attraction for water to the
hydrophilic walls of xylem cells hydrophilic walls of xylem cells
The small diameter of vessels and The small diameter of vessels and
tracheids is important to the adhesion tracheids is important to the adhesion
effecteffect
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iii. Cohesioniii. Cohesion
is the attractive force between molecules of the is the attractive force between molecules of the
same substance. same substance.
 high cohesive force due to the 4 hydrogen bonds high cohesive force due to the 4 hydrogen bonds
water's cohesive force within xylem give it a water's cohesive force within xylem give it a
tensile strength equivalent to that of a steel wire tensile strength equivalent to that of a steel wire
of similar diameter.of similar diameter.
 Cohesion of water allows for the pulling of water Cohesion of water allows for the pulling of water
from the top of the plant without breaking the from the top of the plant without breaking the
"chain"."chain".
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iv. Tensioniv. Tension
a stress placed on an object by a pulling force. a stress placed on an object by a pulling force.
is created by the surface tension which is created by the surface tension which
develops in the leaf's air spaces. develops in the leaf's air spaces.
The upward pull of sap causes tension (negative The upward pull of sap causes tension (negative
pressure) in xylempressure) in xylem
decreases water potential and decreases water potential and
allows passive flow of water from soil into stele allows passive flow of water from soil into stele
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Soil factors affecting water absorptionSoil factors affecting water absorption
Reading AssignmentReading Assignment
Until Next class Until Next class
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1.1.What is the importance of the water potential What is the importance of the water potential
concept in plant physiology? What are the concept in plant physiology? What are the
components of water potential? components of water potential?
2.2.List three unique properties of water that List three unique properties of water that
make it such a good for cellular functioning make it such a good for cellular functioning
3.3.Can plant cells have negative turgor Can plant cells have negative turgor
pressure values? Explain pressure values? Explain
4.4.Describe the casparian strip and its function. Describe the casparian strip and its function.
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