Water Potential and Osmosis in Plants
undefined
•
Water potential
•
Osmotic potential
•
Pressure potential
•
Matric potential
•
Absorption and translocation of
water
•
Stomatal regulation.
undefined
•
Difference b/w free energy of water in that
system and free energy of pure water at
atmospheric pressure and a defined
temperature.
•
Water potential is the potential energy of water
per unit volume relative to pure water in
reference conditions.
•
Water potential quantifies the tendency of water
to move from one area to another due to
osmosis, gravity, mechanical pressure and
matrix effects such as capillary action
•
Unit of measurement: Energy units, Joules per
m
3
, Pascals
•
Pure water
=0
•
Adding solute lowers potential
•
Less free water molecules
•
Water moves from a higher water potential to a
lower water potential
•
Less concentrated (hypotonic) to a more
concentrated (hypertonic)
Osmosis
Movement of
water molecules
from a region of
higher water
potential to a
region of lower
water potential
through a semi-
permiable
membrane.
Diffusion
•
Net movement from
one point to another
because of random
kinetic activities of
molecules or ions
from a region of their
own higher
concentration to a
region of their lesser
concentration.
•
It is spontaneous
process.
Pressure potential
•
Equivalent to
pumpimg water
from one place
to another.
•
If pressure
greater than
atmospheric
pressure is
applied to pure
water or a
solution, its
water potential
increases.
Osmotic potential
•
Solute potential
•
Pressure that a
solution have
to build to
increase its
chemical
potential to
that of pure
water.
•
Solute potential
is always
negative.
Water potential
•
Tendency of
water to leave
the system
•
Higher water
potential,
greater
tendency to
leave
•
Water passes
from one
system to the
other, through
membrane by
osmosis
Water potential = Solute potential + Pressure potential
=
s
+
p
Flaccid:
Limp-lost water
Turgid:
Firm-gained water
Plasmolysis:
Plant cell shrinks from cell wall
Lost water
Deplasmolysis:
Plant cell resumes turgidity
Gained water
E
n
v
i
r
o
n
m
e
n
t
:
0
.
0
1
M
s
u
c
r
o
s
e
0
.
0
1
M
g
l
u
c
o
s
e
0
.
0
1
M
f
r
u
c
t
o
s
e
“
C
e
l
l
”
0
.
0
3
M
s
u
c
r
o
s
e
0
.
0
2
M
g
l
u
c
o
s
e
ψ
=
−
0
.
2
3
M
P
a
(
a
)
0
.
1
M
s
o
l
u
t
i
o
n
P
u
r
e
w
a
t
e
r
H
2
O
ψ
P
=
0
ψ
S
=
0
ψ
P
=
0
ψ
S
=
−
0
.
2
3
ψ
=
0
M
P
a
(
b
)
P
o
s
i
t
i
v
e
p
r
e
s
s
u
r
e
H
2
O
ψ
P
=
0
.
2
3
ψ
S
=
−
0
.
2
3
ψ
P
=
0
ψ
S
=
0
ψ
=
0
M
P
a
ψ
=
0
M
P
a
ψ
P
=
ψ
S
=
−
0
.
2
3
(
c
)
I
n
c
r
e
a
s
e
d
p
o
s
i
t
i
v
e
p
r
e
s
s
u
r
e
H
2
O
ψ
=
0
.
0
7
M
P
a
ψ
P
=
0
ψ
S
=
0
ψ
=
0
M
P
a
0
.
3
0
(
a
)
I
n
i
t
i
a
l
c
o
n
d
i
t
i
o
n
s
:
c
e
l
l
u
l
a
r
ψ
>
e
n
v
i
r
o
n
m
e
n
t
a
l
ψ
ψ
P
=
0
ψ
S
=
−
0
.
9
ψ
P
=
0
ψ
S
=
−
0
.
9
ψ
P
=
0
ψ
S
=
−
0
.
7
ψ
=
−
0
.
9
M
P
a
ψ
=
−
0
.
9
M
P
a
ψ
=
−
0
.
7
M
P
a
0
.
4
M
s
u
c
r
o
s
e
s
o
l
u
t
i
o
n
:
P
l
a
s
m
o
l
y
z
e
d
c
e
l
l
I
n
i
t
i
a
l
f
l
a
c
c
i
d
c
e
l
l
:
ψ
P
=
0
ψ
S
=
−
0
.
7
I
n
i
t
i
a
l
f
l
a
c
c
i
d
c
e
l
l
:
P
u
r
e
w
a
t
e
r
:
ψ
P
=
0
ψ
S
=
0
ψ
=
0
M
P
a
ψ
=
−
0
.
7
M
P
a
ψ
P
=
0
.
7
ψ
S
=
−
0
.
7
ψ
=
0
M
P
a
T
u
r
g
i
d
c
e
l
l
(
b
)
I
n
i
t
i
a
l
c
o
n
d
i
t
i
o
n
s
:
c
e
l
l
u
l
a
r
ψ
<
e
n
v
i
r
o
n
m
e
n
t
a
l
ψ
Ψs = -iCRT
i = ionization constant
Sucrose=1.0 (sucrose does not ionize
water)
C = Molar concentration (from experiment)
R = Pressure constant
(R=0.0831
liter bars/mole K)
T = temperature in K (273 + C)
This content delves into the concept of water potential, osmosis, and pressure potential in plant biology. It explains how water moves within plant cells, the unit of measurement for water potential, the role of osmotic potential in water movement, and the effects of solute concentration on water potential. Additionally, it discusses key terms like turgor pressure, plasmolysis, and flaccid state in plant cells.
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Presentation Transcript
Water potential Osmotic potential Pressure potential Matric potential Absorption and translocation of water Stomatal regulation.
Difference b/w free energy of water in that system atmospheric temperature. Water potential is the potential energy of water per unit volume relative to pure water in reference conditions. Water potential quantifies the tendency of water to move from one area to another due to osmosis, matrix effects such as capillary action and free pressure energy of and pure water defined at a gravity, mechanical pressure and
Unit of measurement: Energy units, Joules per m3, Pascals Pure water =0 Adding solute lowers potential Less free water molecules Water moves from a higher water potential to a lower water potential Less concentrated (hypotonic) to a more concentrated (hypertonic)
Osmosis Movement water from a higher potential region water through a semi- permiable membrane. Osmosis Diffusion Net movement from one point to another because of random kinetic activities of molecules from a region of their own concentration region of their lesser concentration. It process. Diffusion of molecules region of water to of potential or ions higher to a lower a is spontaneous
Water potential = Solute potential + Pressure potential = s + p Osmotic potential Solute potential Pressure that a solution have to build to increase its chemical potential to that of pure water. Solute potential is always negative. Osmotic potential Pressure potential Equivalent to pumpimg water from one place to another. If pressure greater than atmospheric pressure is applied to pure water or a solution, its water potential increases. Pressure potential Water potential Tendency of water to leave the system Higher water potential, greater tendency to leave Water passes from one system to the other, through membrane by osmosis Water potential
Flaccid: Turgid: Plasmolysis: Plant cell shrinks from cell wall Lost water Deplasmolysis: Plant cell resumes turgidity Gained water Limp-lost water Firm-gained water
Environment: 0.01 M sucrose 0.01 M glucose 0.01 M fructose Cell 0.03 M sucrose 0.02 M glucose
(a) 0.1 M solution Pure water H2O P= 0 S= 0 = 0 MPa P= 0 S = 0.23 = 0.23 MPa
(b) Positive pressure H2O P= 0.23 S = 0.23 = 0 MPa P= 0 S= 0 = 0 MPa
(c) Increased positive pressure H2O P = S = 0.23 = 0.07 MPa P= 0 S= 0 = 0 MPa 0.30
Initial flaccid cell: P= 0 S = 0.7 = 0.7 MPa 0.4 M sucrose solution: P= 0 S = 0.9 = 0.9 MPa Plasmolyzed cell P= 0 S = 0.9 = 0.9 MPa (a) Initial conditions: cellular > environmental
Initial flaccid cell: P = 0 S = 0.7 = 0.7 MPa Pure water: P = 0 S = 0 = 0 MPa Turgid cell P = 0.7 S = 0.7 = 0 MPa (b) Initial conditions: cellular < environmental
s = -iCRT i = ionization constant Sucrose=1.0 (sucrose does not ionize water) C = Molar concentration (from experiment) R = Pressure constant (R=0.0831liter bars/mole K) T = temperature in K (273 + C)
