Transcript Water Stress - Academic Resources at Missouri Western

Major Influences on Osmosis

1. Concentration of Solute


Molarity (M)
Osmolarity (O)
Osmotic Potential
the absence of energy in a solution as a
result of solute-solvent interactions, as
compared to pure water
Pure Water O = 0
M=0
O = - 8.1
M = .3
O = - 9.6
M = .35
Major Influences on Osmosis

1. Concentration of Solute


Molarity (M)
Osmolarity (O)
Osmotic Potential
the absence of energy in a solution as a
result of solute-solvent interactions, as
compared to pure water
Pure Water O = 0
M=0
O = -8.1
M = .3
O = - 9.6 M = .35
Osmolarity becomes more negative with
more solute
Major Influences on Osmosis
Osmolarity becomes more neagtive with
more solute
Major Influences on Osmosis


1. Concentration of Solute
2. Pressure from Cell Wall
Wall Pressure (P)


Wall pressure increases with turgidity
Major Influences on Osmosis



1. Concentration of Solute
2. Pressure from Cell Wall
3. Combined Effect


Water Potential (W)
W=O+P
Major Influences on Osmosis



1. Concentration of Solute
2. Pressure from Cell Wall
3. Combined Effect
Water Potential (W)

W=O+P

The true water status of the plants
 Tells how water will move in the tissues
 How tightly the tissue is holding water

Major Influences on Osmosis

3. Combined Effect





Water Potential (W)
W=O+P
W = -8 + 8
W=0
If cells were bathed in pure water
Major Influences on Osmosis

3. Combined Effect

Water Potential (W)

W=O+P

-3 = -11 + P ?
Major Influences on Osmosis

3. Combined Effect

Water Potential (W)

W=O+P

-3 = -11 + P


-3 = -11 + 8,
P=8
Major Influences on Osmosis

3. Combined Effect

Water Potential (W)

W=O+P

-1 = -4 + P ?
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
Major Influences on Osmosis

3. Combined Effect





Water Potential (W)
W=O+P
-1 = -4 + P ?
-1 = -4 + 3, P= 3
Wall pressure must build to +3 to
bring cell into equilibrium with tissue
fluid or cell sap. (only happens at
night)
Major Influences on Osmosis

3. Combined Effect


Water Potential (W)
W=O+P

-14 = -8 + P ?

-14 = -8 + -6, P = -6 ??
Major Influences on Osmosis

3. Combined Effect


Water Potential (W)
W=O+P

-14 = -8 + P ?

-14 = -8 + -6, P = -6 ??

Plasmolysis - Wilting
Major Influences on Osmosis

3. Combined Effect


Water Potential (W)
W=O+P

-8 = -8 + P ?

-14 = -8 + 0, P = 0 ??


Isotonic – on the verge of plasmolysis
Just prior to incipient plasmolysis
Major Influences on Osmosis

3. Combined Effect



Water Potential (W)
W=O+P
If we just conside water in a container –
not in a cell,

Pure Water W = 0

Salt Water
W = some number less than
zero
Major Influences on Osmosis

3. Combined Effect



Water Potential (W)
W=O+P
For measuring the W of plant tissue the
most direct and most accurate method is
the use on a ________________.
Major Influences on Osmosis

3. Combined Effect



Water Potential (W)
W=O+P
For measuring the W of plant tissue the
most direct and most accurate method is
the use on a pressure bomb.
Ascent of Water in Plants


Water Potential Gradient
1. Root Pressure

due to accumulation of solute in the stele
Ascent of Water in Plants


Water Potential Gradient
1. Root Pressure

due to accumulation of solute in the stele
Ascent of Water in Plants


Water Potential Gradient
1. Root Pressure

due to accumulation of solute in the stele
Ascent of Water in Plants


Water Potential Gradient
1. Root Pressure

due to accumulation of solute in the stele
Ascent of Water in Plants


Water Potential Gradient
1. Root Pressure

due to accumulation of solute in the stele
Ascent of Water in Plants


Water Potential Gradient
1. Root Pressure



due to accumulation of solute in the stele
The positive pressure that builds up in the root may
extend to the stem & leaves. -> GUTTATION
Hydathodes
Ascent of Water in Plants

Water Potential Gradient
1. Root Pressure

2. Capillary Action


Cohesion and Adhesion
Ascent of Water in Plants



Water Potential Gradient
1. Root Pressure
2. Capillary Action
3. Cohesion – Tension
a. transpiration
mesophyll cells -> water vapor into
substomatal chamber -> through stomates
-> through boundary layer air -> into air
b. W of mesophyll cells decreases
Ascent of Water in Plants



Water Potential Gradient
1. Root Pressure
2. Capillary Action
3. Cohesion – Tension *
a. transpiration
b. W of mesophyll cells decreases
c. mesophyll cells draw water from xylem
in vein
d. “transpirational pull” due to
cohesion of water molecules -> tension
Stomates

Structure
Stomates


1 -> 3% of leaf surface
Guard Cells (2)
chloroplasts
 thickened inner walls usually



Pore mechanism
Little cuticle – peristomatal transpiration

Accessory Cells

Regulated Movement –

Helps to prevent excessive water loss
Stomates

Structure
Stomates
Xerophytic Plants adaptations?
stomatal regulation
Stomates
Xerophytic Plants
- controlled stomatal movements
- fewer stomates
- sunken stomates
- thick cuticle
- hairiness
holds boundary layer
reflects light
Stomates
- As a plant dries out … stomates close
Stomates
Classical Theory of Stomatal Action:
1.
Photosynthesis
2.
H2C03 decreases pH increases
3.
Starch - Glucose
4.
Increased Glucose has Osmotic Effect on
Guard Cells
5.
Stomates Open
Stomates
Ion Flux Theory of Stomatal Action:
1.
Active Transport of K+ from surrounding
cells into the guard cells (other ions, Cl-, …
also involved)
2.
Increased K+ causes Osmotic Effect on
Guard Cells
3.
Stomates Open
Stomates
Guard Cell – Accessory Cell Relationship
Methods for Detecting and
Measuring Transpiration
48’ silver maple = 58 gals./hour
1.
Weighing Methods
2.
Potometer methods
1.
2.
3.
Direct Measurement of the Amount of Water
Absorbed by the Plant
Assumption: the amt. of water absorption
equals the amt. of transpiration
Cuvette Methods
1.
2.
Single leaf or branch part enclosed in chamber
– monitor gas exchange and humidity
Tent Chambers (absolute transpiration)
Methods for Detecting and
Measuring Transpiration
4. Cobolt Chloride Paper
blue < Red
5. Porometer
indirect measurement through stomatal
resistance
Factors Affecting Stomatal
Resistance and Transpiration Rate
1.
Water Stress –
peristomatal transpiration
cuticular transpiration
stomatal transpiration
ABA from mesophyll cells – causes
egress of K+ from guard cells
CLOSURE OF STOMATES BEFORE WILTING
“wilty mutant” tomato
ABA down
Factors Affecting Stomatal
Resistance and Transpiration Rate
1. Water Stress –
2. Carbon Dioxide –
CO2 low in substomatal chamber ->
stomates open
cell respiration – produces CO2 ->
stomates close
Why open stomates without photosynthesis?
Factors Affecting Stomatal
Resistance and Transpiration Rate
1. Water Stress –
2. Carbon Dioxide –
3. Temperature –
stomates generally open 0 -> 30/35
degrees centigrade if light
day: photosyn. up/resp. down
stomatal resistance (SR)
Factors Affecting Stomatal
Resistance and Transpiration Rate
1. Water Stress –
2. Carbon Dioxide –
3. Temperature –
Factors Affecting Stomatal
Resistance and Transpiration Rate
1. Water Stress –
2. Carbon Dioxide –
3. Temperature –
Factors Affecting Stomatal
Resistance and Transpiration Rate
1. Water Stress –
2. Carbon Dioxide –
3. Temperature –
stomates generally open 0 -> 30/35
degrees centigrade if light
day: photosyn. up/resp. down
Factors Affecting Stomatal
Resistance and Transpiration Rate
1.
2.
3.
4.
Water Stress –
Carbon Dioxide –
Temperature –
Light C3 plants
C4 plants, CAM plants
CO2 -> 4-carbon acids -> CO2
-> Calvin Cycle (RuBP)
Transpiration, Stem Flow and Leaf
WP in Larix
Factors Affecting Stomatal
Resistance and Transpiration Rate
1.
2.
3.
4.
5.
Water Stress –
Carbon Dioxide –
Temperature –
Light Humidity -
Factors Affecting Stomatal
Resistance and Transpiration Rate
5. Humidity Relative Humidity RH%
Vapor Pressure VP
The same RH readings may have different VPs
depending on the temperature.
Substomatal Chamber – near 100% RH –
VP depends largely on Temperature
Stomates sometimes close due to large VP
differences between the leaf and air.
Factors Affecting Stomatal
Resistance and Transpiration Rate
5. Humidity Relative Humidity RH%
Vapor Pressure VP
The same RH readings may have different VPs
depending on the temperature.
Factors Affecting Stomatal
Resistance and Transpiration Rate
5. Humidity 6. Wind –
Factors Affecting Stomatal
Resistance and Transpiration Rate
5. Humidity 6. Wind –
7. Plant Factors –
Factors Affecting Stomatal
Resistance and Transpiration Rate
5.
6.
7.
8.
Humidity Wind –
Plant Factors –
Endogenous Rhythms -
Soil Factors in Water Absorption
1.
Temperature
1.
2.
Aeration”
1.
3.
TKE Cell Metabolism
Oxygen
“flopping
Soil particle Size
1.
SAND
SILT
clay
Soil Factors in Water Absorption
1.
2.
3.
Temperature
Aeration
Soil particle Size
1.
SAND
SILT
CLAY
Soil Factors in Water Absorption
1.
2.
3.
4.
Temperature
Aeration
Soil particle Size
Water Potential of the soil
1.
W=O+m
Water and Mineral Absorption by
the Plant
Water and Mineral Absorption by
the Plant
Rhizosphere
Mucilage
secreted from root cells
Mucigel
bacteria + fungi
Zone of Mineral Depletion
Water and Mineral Absorption by
the Plant
Water and Mineral Absorption by
the Plant
Micorrhiza ectomicorrhiza
endomycorrhiza
Host Specificity – (lodgepole pines)
Water and Mineral Absorption by
the Plant
Water and Mineral Absorption by
the Plant
Soil Mineral Nutrients
Water and Mineral Absorption by
the Plant
Soil Mineral Nutrients
N, P, K
*Essential Elements
*Beneficial Elements
Si, Se, Na, Co
Water and Mineral Absorption by
the Plant
Water and Mineral Absorption by
the Plant
Soil Reservoir
charged particles (-)
ion exchange
binding affinity
anions (-) not held
concentration (gradient)
Water and Mineral Absorption by
the Plant
Soil Reservoir
Lyotropic Series
(acid rain…) cations
Water and Mineral Absorption by
the Plant
Soil Reservoir
Lyotropic Series
(acid rain…) cations
Water and Mineral Absorption by
the Plant
Availability of Water
Field Capacity
water content of the soil after it has been
thoroughly wetted and allowed to drain until
the capillary movement of the water has ceased
Permanent Wilting Point
amount of water left in the soil when the leaves first
begin to show signs of permanent wilting
Water and Mineral Absorption by
the Plant
Availability of Water
Field Capacity
Permanent Wilting Point
Total Soil Moisture Stress TSMS
sum of the osmotic potential of the soil (O) and
the soil moisture tension (m)
W=O+m
Soil Tensiometer
Water and Mineral Absorption by
the Plant
Water and Mineral Absorption by
the Plant
Water and Mineral Absorption by
the Plant
Water and Mineral Absorption by
the Plant