Water Movement, Translocation and Nutrient Uptake

1
Water Movement, Translocation and Nutrient Uptake
Chapters 36 and 37
2
Introduction flow of substances

• Driving force
• Concentration gradients
• Electrical gradients
• Pressure gradients
• Pathway
• Length
• Resistance

3
Ficks Law

• fx F/(dR)
• Where
• fx flux
• F gradient
• d distance
• R resistance

4
Establishing a gradient - Components of Water
potential (the potential for water to do work)

• ? (total water potential)
• ?s (osmotic or solute potential)
• ?p (pressure potential)
• ?m (matric potential)
• ?g (gravimetric potential)
• ? ?s ?p (?m ?g)
• generally not considered in plant water balance

5
Interaction of the components of water potential
- I
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Interaction of the components of water potential
- II

Pressure potential
MPa
decreasing cell volume
Total water potential
-
Osmotic potential (solute potential)
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Total water potential
Difference between lines equals pressure potential
Theoretical ? potential
Turgor loss potential
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Flow in soil, plant, atmosphere continuum

• Electrical circuit analogy Ohms law
• VIR
• Where
• V voltage
• I current
• R resistant
• Rearranged I V/R
• Ficks law
• fx F/dR
• Where
• fx volumetric water flow through plant
• F water potential gradient between atmosphere
  and soil
• dR resistances to water movement in plant

10
Water potential of atmosphere at various
relative humidities
Minimal WP values for various plants

10 bars 1 MPa
11
Soil water relations - films and adhesion
10 atms is approximately 1 MPa
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Movement of water within plant - films and
cohesion and adhesion
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Translocation
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Direction and mechanism

• Flow is from a source (region of production) to a
  sink (region of use).
• Sieve tubes actively loaded at source lowering
  water potential drawing in water.
• Pressure drives water and materials through
  tubes.
• Sieve tubes actively unloaded at sink raising
  water potential resulting in loss of water.
• Water goes into xylem to be returned.

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Water balance and sap-flow in red alder and big
leaf maple
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The Team
David W.
David H.
Tara and Megan
Myst
Angela and Seth
Jenny
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Measurement of gas exchange and water potential
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Measuring Sap-flow
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Measuring Hydraulic Conductance
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big leaf maple
red alder
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Nutrient Uptake
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Transfer across membranes
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Soil structure - Clay particles
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Movement locations in transfer of material

• Apoplast area outside cell membrane including
  the cell wall
• Symplast area inside cell membrane

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35
Solutions to the Nutrient Problems

• Nitrogen fixation
• Mycorrhizae
• Parasite/saprophyte
• Carnivory

36
Nitrogen fixation
37
Mycorrhizae
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Parasite/Saprophyte
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Carnivory
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The End