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 = M =.3 O = 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 = 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 = W = 0 If cells were bathed in pure water

Major Influences on Osmosis  3. Combined Effect Water Potential (W) W = O + P -3 = P ?

Major Influences on Osmosis  3. Combined Effect Water Potential (W) W = O + P -3 = P -3 = , P = 8

Major Influences on Osmosis  3. Combined Effect Water Potential (W) W = O + P -1 = -4 + P ?

Major Influences on Osmosis  3. Combined Effect Water Potential (W) W = O + P -1 = -4 + P ? -1 = , 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 = , P = -6 ??

Major Influences on Osmosis  3. Combined Effect Water Potential (W) W = O + P -14 = -8 + P ? -14 = , P = -6 ?? Plasmolysis - Wilting

Major Influences on Osmosis  3. Combined Effect Water Potential (W) W = O + P -8 = -8 + P ? -14 = , 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. Direct Measurement of the Amount of Water Absorbed by the Plant 2. Assumption: the amt. of water absorption equals the amt. of transpiration 3. Cuvette Methods 1. Single leaf or branch part enclosed in chamber – monitor gas exchange and humidity 2. 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. Water Stress – 2. Carbon Dioxide – 3. Temperature – 4. 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. Water Stress – 2. Carbon Dioxide – 3. Temperature – 4. Light - 5. 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. Humidity - 6. Wind – 7. Plant Factors – 8. Endogenous Rhythms -

Soil Factors in Water Absorption 1. Temperature 1. TKE Cell Metabolism 2. Aeration” 1. Oxygen“flopping 3. Soil particle Size 1. SAND SILTclay

Soil Factors in Water Absorption 1. Temperature 2. Aeration 3. Soil particle Size 1. SAND SILTCLAY

Soil Factors in Water Absorption 1. Temperature 2. Aeration 3. Soil particle Size 4. Water Potential of the soil 1. W = O + m

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

Micorrhiza - ectomicorrhiza endomycorrhiza Host Specificity – (lodgepole pines)

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

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